解聚型魔芋葡甘露聚糖的制备以及生理活性研究的进展

Depolymerized konjac glucomannan: preparation and application in health care 解聚型魔芋葡甘露聚糖的制备以及生理活性研究的进展 1 first-author 1 1 2 corresp ‡Corresponding Author ‡Corresponding Author †E-mail:shijs@163.com †E-mail:shijs@163.com shijs@163.com 3 4 School of Pharmaceutical, Jiangnan University, Wuxi 214122, China School of Pharmaceutical, Jiangnan University, Wuxi 214122, China Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Pharmaceutical Science, Jiangnan University, Wuxi 214122, China Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Pharmaceutical Science, Jiangnan University, Wuxi 214122, China National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China School of Biotechnology, Jiangnan University, Wuxi 214122, China School of Biotechnology, Jiangnan University, Wuxi 214122, China Konjac glucomannan (KGM) is a water-soluble polysaccharide obtained from the roots and tubers of konjac plants. Recently, a degraded product of KGM, depolymerized KGM (DKGM), has attracted attention because of its low viscosity, improved hydrophily, and favorable physiological functions. In this review, we describe the preparation of DKGM and its prebiotic effects. Other health benefits of DKGM, covering antioxidant and immune activity, are also discussed, as well as its safety. DKGM could be a candidate for use as a tool for the treatment of various diseases, including intestinal flora imbalance, and oxidative-and immune-related disorders. 魔芋葡甘露聚糖是从魔芋块茎中提取的一种高分子水溶性多糖.近些年研究表明,其解聚产物,除了具有高溶解性和低粘度等良好的理化性质外,还具有调节微生物菌群结构、抗氧化、免疫调节等多种生理活性.本文重点综述了解聚型葡甘露聚糖的制备方法以及菌群调节功能.除此之外,对其抗氧化、免疫调节功能以及安全性评价也进行了全面的总结,为解聚型葡甘露聚糖的研究与应用提供一定的依据与思路. Konjac glucomannan Depolymerized konjac glucomannan Prebiotics Immune response Antioxidant 魔芋葡甘露聚糖 解聚型魔芋葡甘露聚糖 益生功能 免疫活性 抗氧化 Introduction 1 Konjac glucomannan (KGM) is a water-soluble polysaccharide obtained from the roots and tubers of the konjac plant ( Amorphophallus konjac ). It consists of D -mannose and D -glucose units at a molar ratio of about 1.6:1.0. These units are joined by β-(1,4)-glycosidic bonds to form the backbone, and a few branches are formed by β-(1,6)-glycosidic units. Part of the short side branches can be formed via linkage between the C-3 positions of the mannoses and the acetyl groups randomly found at the C-6 position of a sugar unit. These sugar units with acetyl groups comprise about 1/9th to 1/20th of the total sugar units. Owing to its high molecular weight (mostly ranging from 1×10 4 to 2×10 6 Da) (Al-Ghazzewi et al., 2007 2007 ) and non-caloric nature, KGM plays a beneficial role in blood cholesterol and sugar reduction, weight loss, promotion of intestinal activity and immune function. Therefore, KGM has been consumed for centuries in East Asia, but in low-added value food forms, such as KGM tofu, noodles, and jellies. Recently, many researchers have studied the preparation of depolymerized KGM (DKGM) (Behera and Ray, 2016 2016 ; Tester and Al-Ghazzewi, 2017 2017 ). Compared with native KGM, DKGM showed significantly reduced viscosity, which is more favorable for food processing. Besides, DKGM displays many unique biological characteristics, especially its prebiotic function. Because of these advantages, DKGM has attracted increasing attention. In this review, we discuss its preparation strategies, safety concerns, and biological function assessments, including its prebiotic, antioxidant, and immune-regulator effects. Factors affecting the extent of its physiological benefits are also discussed. Preparation techniques 1 Recently, a number of studies have been devoted to exploring efficient methods for degrading KGM. In general, these methods can be divided into two classes: physicochemical degradation and biodegradation Physicochemical degradation 2 Various physicochemical degradation methods, such as acid-treatment (Suzuki et al., 2010 2010 ), thermal treatment (Jin et al., 2014b 2014b ), oxidative degradation (Zheng et al., 2015 2015 ; Zhang et al., 2016 2016 ), ultrasound treatment (Huang et al., 2006 2006 ; Li et al., 2017 2017 ), and irradiation treatment (Xu et al., 2007 2007 ; Jian et al., 2013 2013 , 2017 2017 ; Pan et al., 2013 2013 ; Li et al., 2018 2018 ), have been used to degrade polysaccharides. Although strong acid is powerful in breaking down the glycosidic chains of KGM, the process is not very controllable and carries a high risk of environment pollution. The use of γ-rays is a simple and manageable way to degrade polysaccharides in any physical form (e.g. solid, suspension, paste, or solution) without heating. The ionizing energy can rapidly penetrate the granule and randomly rupture the backbone of KGM. However, the molecular mass distribution of the final product is broad. Degradation of KGM by irradiation is believed to be dose-dependent (Xu et al., 2007 2007 ; Jian et al., 2013 2013 , 2017 2017 ). While there is agreement among international experts that irradiation dosages up to 10 kGy are safe (Jian et al., 2013 2013 , 2017 2017 ; Jin et al., 2014a 2014a ), carbonyl groups and double bonds might be formed at relatively high irradiation doses, leading to browning of the final product (Xu et al., 2007 2007 ). Therefore, irradiation dosage is the priority consideration during the process. Besides irradiation dosage, the solvent used to dissolve KGM is important. A higher efficiency of KGM degradation by irradiation is observed in some solvents than that found by irradiation alone. For example, the hydrogen peroxide solution alone cannot degrade KGM efficiently, but produces hydroxyl radicals, and the concentration of hydroxyl radicals increases after irradiation. The hydroxyl radicals are powerful oxidative agents, and could directly break the glucosidic linkages of KGM by absorbing carbon-bound hydrogen atoms. Therefore, the molecular weights of products with irradiation alone (6.58×10 4 Da) and synergetic degradation (6.48×10 4 Da) are much lower than that of the untreated sample (4.80×10 5 Da) (Pan et al., 2013 2013 ). Nevertheless, many factors are involved in the process: (1) free radicals, generated by the solvent, probably play either a positive or negative role in radiation; (2) molecular conformation varies with the solvent type and concentration. For instance, KGM molecular conformation and hydrogen atoms played a restrained effect during KGM irradiation in ethanol. At low irradiation doses, stability predominated, leading to the viscosity-average molecular weights of pre-immersed samples being higher than those of irradiation controls. However, at high doses, the inhibition effect was relatively less significant, and the irradiation effect played a leading role in the hydrolysis process. For this reason there was no significant difference between ethanol-treated and untreated groups (Jin et al., 2014a 2014a ). So far, there have been only a few studies of the use of ultrasound degradation of KGM. It was thought that ultrasound treatment could weaken the intermolecular interactions between KGM molecules in an aqueous solution as well as the intramolecular interactions between the KGM polymer chains, leading to their degradation. The changes in the structure and degradation of KGM depended on the ultrasound power and other treatment parameters (Huang et al., 2006 2006 ; Chen and Qian, 2008 2008 ). Moreover, the degradation process of KGM by ultrasound was deemed to fit first-order polymer degradation kinetics (Li et al., 2017 2017 ). Enzyme hydrolysis 2 Compared with physicochemical degradation, enzymes have been widely used in polysaccharide hydrolysis because of their advantages such as high extraction yield, reproducibility, environmental-friendliness, energy efficiency, and simple protocols (van Zyl et al., 2010 2010 ; Bhotmange et al., 2017 2017 ; Jiao et al., 2017 2017 ). The molecular structure of KGM can provide multiple cutting sites. Thus, it can be degraded by different enzymes (Chen J et al., 2013 2013 ; Jian et al., 2013 2013 ; Mikkelson et al., 2013 2013 ; Liu HX et al., 2015 2015 ; Chen CY et al., 2016 2016 ; Yang et al., 2017 2017 ). Cellulase and hemicellulase derived from different strains have been most well studied so far (Table 1 1 ). The commercial cellulase product (a mixture of endoglucanase, exoglucanase, and glucosidase) has been the enzyme most commonly used for KGM hydrolysis. In the mixed product, the glucanase can break the β-(1,4)-glycosidic bond between glucose and mannose, the exoglucanase can remove the 1,4-glucopyranose units at the non-reducing end, and the β-glucosidase can cleave glucobiose into glucose units (Zhang et al., 2003 2003 ). As for the hemicellulase, β-mannanase has been the most commonly used enzyme. It is an endo-acting hydrolase which acts by randomly catalyzing the β-(1,4)-mannosidic linkages, resulting in the production of DKGM (Dhawan and Kaur, 2007 2007 ; van Zyl et al., 2010 2010 ; Liu HX et al., 2015 2015 ). Therefore, the choice of enzyme determines the structural characteristics of the final product. For example, M(mannan)G(glucose), MM, MMG, and MMM are abundant when KGM is hydrolyzed by endoglucanase, whereas plenty of GM, MM, GGM, and GMM are obtained by using β-mannanase (Cescutti et al., 2002 2002 ). Consistent with this, 99% of DKGM obtained from catalysis by β-mannanase had M as the reducing end pyranosyl unit, while KGM hydrolyzed by endoglucanase had both M and G as the reducing end pyranosyl unit (Mikkelson et al., 2013 2013 ). E/S: the ratio of enzyme to substance; DP: degree of polymerization Category Origin Reaction condition Product information Reference 17 Hemicellulase pH 6.5, 20% konjac, 45 °C, E/S 250 U/g, 0.83 h KGM oligosaccharide yield 35%, mainly consists of triose and tetrose units He et al., 2013 2013 Aspergillus niger pH 4.2, 2% konjac, 65 °C, E/S 108 U/g, 4 h KGM oligosaccharide yield 32.3% Xu et al., 2005 2005 A . niger pH 7.0, 15% konjac, 50 °C, E/S 50 U/g, 6 h KGM oligosaccharide yield 100% after yeast fermentation Li et al., 2007 2007 A . niger pH 7.0, 24% konjac, 50 °C, E/S 120 U/g, 8 h The average DP of DKGM was 1.8–1.9 Xu et al., 2008 2008 A . niger pH 5.0, 1% konjac, 30 °C, E/S 46.2 U/g, 24 h Oligosaccharide covering the whole range of DP 3–9 Albrecht et al., 2009 2009 pH 5.5, 1% konjac, 45 °C, E/S 100 U/g, 1.5 h KGM oligosaccharide yield 100% after yeast fermentation Wu et al., 2010 2010 A . niger pH 3.5–8.5, 0.05%–3.05% konjac, 14–62 °C; 20% konjac, 0.04–1.00 h The molecular weight and molecular weight distribution depended on the enzymatic parameters Yao et al., 2011 2011 A . niger pH 3.5, 18% konjac, 65 °C, E/S 30 U/g, 4 h KGM oligosaccharide yield 35.73% after yeast fermentation Xu SC et al., 2011 2011 Bacillus subtilis pH 6.0, 12.5% konjac, 50 °C, E/S 200 U/g, 3 h Xu LP et al., 2011 2011 B . subtilis pH 7.5, 5% konjac, 45 °C, E/S 50 U/g, 24 h Oligosaccharide covering the whole range of DP 2–9 Kang et al., 2012 2012 pH 6.0, 61.3% konjac, 55 °C, E/S 1500 U/g, 4.2 h DKGM yield 76.34% after ethanol precipitate, galactopyranose type DKGM covering the whole range of DP 2–10 Qin et al., 2013 2013 pH 6.0, 61.3% konjac, 55 °C, E/S 1500 U/g, 4.2 h DKGM yield 52.67% Deng et al., 2013 2013 Trichoderma reesei pH 5.0, 1% konjac, 45 °C, 48 h 17% DKGM (DP 2–6) Mikkelson et al., 2013 2013 pH 7.1, 20% konjac, 41 °C, E/S 0.49, 3.4 h Chen et al., 2013 2013 Thermobifida fusca 50 °C, 24 h The weight-average molecular weight 3089 Da Cheng et al., 2016 2016 pH 4.0, 0.2% konjac, 50 °C, E/S 360 kU/g, 24 h The molecular mass lower than 2200 Da after combination of γ-irradiation and enzymatic hydrolysis Jian et al., 2013 2013 B . subtilis pH 7.0, 0.33% konjac, 60 °C, E/S 6 U/g, 1 h DKGM yield 35.96%, most DKGM with DP 2–6 Cheng et al., 2016 2016 5 6 Cellulase Trichoderma viride pH 5.0, 10% konjac, 40 °C, E/S 50 U/g, 2 h Weight-average molecular weight 7160 Da, number-average molecular weight 5100 Da Zhang et al., 2003 2003 pH 4.5, 10% konjac, 60 °C, E/S 450 U/g, 1 h Elamir et al., 2008 2008 T . viride pH 5.0, 1% konjac, 30 °C, 24 h Albrecht et al., 2009 2009 pH 3.5, 0.5% konjac, 30 °C, E/S 58 U/g, 24 h Oligosaccharide covering the whole range of DP 3–14 Albrecht et al., 2009 2009 10% konjac, 50 °C, 1.3 h Dang et al., 2015 2015 T . reesei pH 5.0, 1% konjac, 45 °C, 48 h 18.0%, 4.7% DKGM (DP 2–6) for Cel7A and Cel7B, respectively Mikkelson et al., 2013 2013 Compared with enzymatic hydrolysis alone, chemical and physical pretreatments enhance the KGM enzymatic degradation process. Jian et al. ( 2013 2013 ) found that the molecular weight of KGM (1.68×10 6 Da) following γ-irradiation pre-treatment could be further reduced to 2200 Da with enzymes. Similarly, the molecular weight distribution of KGM enzymatic hydrolysis with or without mechanical shear pre-treatment was investigated. Compared with non-treated controls, the average molecular weights of the supernatant and pellet of DKGM following mechanical shear pre-treatment were further reduced by nearly 5% and 35%, respectively (Yang et al., 2017 2017 ). Although enzymatic degradation has been widely studied, most of these studies aimed mainly to reduce the molecular weight of KGM, and there is lack of information about its structure and purity. We believe that the health benefits of DKGM are closely associated with its molecular characteristics (e.g. its molecular structure and degree of polymerization (DP)). Therefore, controllable and limited enzymatic degradation as well as product purification is still the most challenging problems in its application. Safety 1 It is widely regarded that overconsumption of oligosaccharides might induce flatulence and even cause an imbalance of essential nutrients, which would be counterproductive (Liu et al., 2016 2016 ). Although the intrinsic safety of DKGM is supported by its natural occurrence in konjac, the safety of DKGM is still worthy of investigation. So far, only a few studies of DKGM safety have been reported. A previous study by our research group demonstrated that DKGM (DP=2–7) of up to 7.5 g/kg daily was safe for rats for 90 d. The results of genotoxicity studies in vitro (using the Ames assay and erythrocyte micronucleus assay) and in vivo (using a sperm malformation test in mice) indicated that administration of DKGM up to 10.0 g/kg had no mutagenic potential. In addition, DKGM up to 2.5 g/kg showed neither maternal toxicity nor teratogenicity in pregnant rats (Jiang et al., 2016 2016 ). Biological activity 1 More recently, DKGM, especially low molecular weight DKGM, has been widely studied because of its health benefits. In this part, its prebiotic effects and relevant factors are summarized. Potential applications of DKGM in the fields of anti-oxidation and immune function are also discussed. Prebiotic activity 2 The prebiotic activity of DKGM has been mentioned briefly in some reviews which focused mainly on native KGM (Bateni et al., 2013 2013 ; Behera and Ray, 2016 2016 ; Tester and Al-Ghazzewi, 2017 2017 ). In general, recent studies (Table 2 2 ) revealed that DKGM is valuable as a prebiotic via a number of mechanisms: (1) It can selectively stimulate Lactobacillus and Bifidobacterium in the colon (Feng et al., 2015 2015 ; Liu et al., 2016 2016 ), cecum (Wang et al., 2016a 2016a ), vagina and skin surface (Tester et al., 2012 2012 ). (2) By blocking their adhesion on mucosal surfaces of animals, DKGM can restrain the growth of pathogenic bacteria such as Coliforms , Enterococci , Staphylococcus aureus (Al-Ghazzewi et al., 2012 2012 ; Liu et al., 2016 2016 ), Propionibacterium acnes (Al-Ghazzewi and Tester, 2010 2010 ), Clostridium (Chen et al., 2005 2005 ), and Salmonella typhi (Al-Ghazzewi et al., 2012 2012 ). (3) During the fermentation of DKGM, short chain fatty acids (SCFAs) (mainly acetic, propionic, and butyric acid) are generated, leading to a lowering of the gut pH. These SCFAs are a source of nutrition for gut microbes, and show positive effects for the treatment of inflammation and carcinogenesis in the gut and other organs (Tester et al., 2012 2012 ; Bateni et al., 2013 2013 ; Wan et al., 2015 2015 ; Sivaprakasam et al., 2016 2016 ; Tao et al., 2016 2016 ; Unger et al., 2016 2016 ; Primec et al., 2017 2017 ). DP: degree of polymerization; IBD: inflammatory bowel disease; SCFA: short chain fatty acid Test Substance Subject Prebiotic effect Reference 3 9 In vitro DP 10–70 Single microculture Enhanced all Lactobacillus and Bifidobacterium strains examined Al-Ghazzewi et al., 2007 2007 Reduced Propionibacterium Al-Ghazzewi and Tester, 2010 2010 Molecular weight 1000–6000 Da Microculture with human faeces Selective stimulation of beneficial gut microbiota and a favourable SCFA profile Connolly et al., 2010 2010 Containing less than 10% by weight degree of DP 3 Single microculture Enhanced lactic acid bacteria Al-Ghazzewi and Tester, 2012 2012 Molecular weight 1000–6000 Da Co-microculture Reduced Staphylococcus aureus and Salmonella typhimurium Al-Ghazzewi et al., 2012 2012 2000 u, 5000 u, 10000 u Single microculture Enhanced the proliferation of Lactobacillus acidophilus Wang et al., 2015 2015 DP 2–6 Single microculture Enhanced four different lactic acid bacteria Wang et al., 2016b 2016b Co-microculture Lactobacillus plantarum was the dominant strain in the co-culture with Enterococcus Guo et al., 2017 2017 Microculture with human faeces Improved the composition of fermentation broth and the prebiotic effect can be enhanced by γ-irradiation Li et al., 2017 2017 7 3 10 In vivo Mice Enhanced anaerobes and Lactobacillus ; reduced Clostridium perfringens and Escherichia coli Elamir et al., 2008 2008 Female patients suffering from vaginal infection Decreased the clue cells and yeast-like fungi Tester et al., 2012 2012 Female patients suffering from acne vulgaris Improved skin health Bateni et al., 2013 2013 Molecular weight <10 000 Da and >10 000 Da Patients suffering IBD Improve the patients’ life style Suwannaporn et al., 2013 2013 DP 2–10 Mice Enhanced Bifidobacterium and Lactobacillus Qin et al., 2014 2014 DP 2–10 ≥85%, DP 2–6 ≥50% Ulcerative colitis mice Decreased the ulcer areas and rates of the colon Feng et al., 2015 2015 DP 2–4 Mice Improved the gut environment; enhanced the probiotics Wan et al., 2015 2015 DP 2–4 Rat Improved the intestinal environment; regular intestinal flora Wang et al., 2016a 2016a DP 2–10 ≥85%, DP 2–6≥50% Ulcerative colitis rat Improved the gut environment; improved the gut microbiota structure; anti-inflammatory Liu et al., 2016 2016 DP 2–10 ≥85% Ulcerative colitis rat Improved the gut environment; improved the gut microbiota structure Liu et al., 2017 2017 Generally, the fermentation process of DKGM is a time-and dose-dependent procedure (Tester et al., 2012 2012 ; Behera and Ray, 2016 2016 ). The DP, structural characteristics, and constituents of DKGM change with the preparation methods, often leading to different fermentation behaviors (Wang et al., 2008 2008 ; Albrecht et al., 2009 2009 ). Four substrates (a monomer-free DKGM with a cellulose digest, a monomer-free DKGM with an endo-β-(1,4)-glucanase digest, a monomer-containing DKGM with a cellulose digest, and native KGM) were fermented in a fecal slurry consisting of a mix of feces from three human volunteers for 72 h. Optical density and pH showed that all DKGM were fermented well except native KGM. The monomer-free endo-β-(1,4)-glucanase digest behaved similarly to the cellulose digests. However, the fermentation of the monomer-free cellulose digest showed a different pattern compared to the monomer-containing digest. For the monomer-free digest, the monomers were fermented during the first 24 h, and then most of the dimers and trimers were fermented between 24 and 72 h. No significant change was observed for the larger oligomers. In contrast, for the monomer-containing cellulose digest, no change was observed in the first 24 h. Moreover, DP 6 was completely degraded and DP 5 mostly degraded between 24 and 72 h, whereas DP 4 was more resistant (Albrecht et al., 2009 2009 ). Similarly, DKGM with a different structure and constituent was obtained following treatments with endo-β-(1,4)-glucanase, endo-β-(1,4)-mannanase, and an equivalent mixture (1:1) of cellulose-mannanase. Their utilization by lactic acid bacteria was then evaluated. The Lactobacillus growth profiles showed that DKGM produced with cellulose enzymes was the most effective growth promoter among the three groups (Al-Ghazzewi and Tester, 2012 2012 ). Although lots of research has demonstrated the prebiotic effect of DKGM, its selectivity towards specific microorganisms and the fermentation profile are still unclear. According to Wang et al. ( 2016b 2016b ) and Yang et al. ( 2017 2017 ), the fermentation of DKGM varies among species. DKGM with different molecular weights was prepared by mechanical-pretreated enzymatic hydrolysis, and fermentation by five Lactobacillus and three Bifidobacterium was investigated in vitro. Results showed that all the test bacteria (except Lactobacillus delbrueckii subsp. bulgaricus ) were DKGM fermenters, but Bifidobacterium strains were not as strong as Lactobacillus . Moreover, there was variation among the Lactobacillus strains (Yang et al., 2017 2017 ). Similarly, Wang et al. ( 2016b 2016b ) investigated the regular fermentation patterns of DKGM by four acid bacteria ( Lactobacillus animals , Lactobacillus plantarum , Enterococcus faecalists , and Lactobacillus reuteri ) in vitro. Results showed that L. plantarum and E. faecalists could quickly and completely consume DKGM with DP 2–3, whereas L. animals and L. reuteri utilized only the DKGM with DP2. In vivo studies in healthy animals (Elamir et al., 2008 2008 ; Qin et al., 2014 2014 ; Wan et al., 2015 2015 ; Wang et al., 2016a 2016a ), ulcerative colitis animals (Feng et al., 2015 2015 ; Liu et al., 2016 2016 ), and humans suffering from IBD (Suwannaporn et al., 2013 2013 ) (Table 2 2 ) verified the prebiotic effects of DKGM. Mechanism studies revealed that oral administration of DKGM not only promotes the proliferation of probiotics (mainly Lactobacillus and Bifidobacterium ), which is consistent with the in vitro results, but also influences the intestinal environment (increasing intestinal villi height and SCFAs) and reduces the levels of inflammatory factors (malondialdehyde, inducible nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β)). Furthermore, the physiological effects of DKGM in the gut were verified to be effective in the skin and vagina of humans (Tester et al., 2012 2012 ; Bateni et al., 2013 2013 ), implying that the use of DKGM can be expanded to other ecological systems beyond the gut. Anti-oxidative activity 2 In recent years, there has been increasing interest in natural antioxidants because synthetic antioxidants might induce teratogenicity, carcinogenicity or mutagenicity. A few studies have demonstrated that DKGM could have great potential as a natural antioxidant (Wang et al., 2008 2008 ; Liu J et al., 2015 2015 ; Jian et al., 2017 2017 ). In general, its anti-oxidative effects may result from two pathways: (1) It could act directly as an antioxidant which not only scavenges oxidants, but also activates intracellular antioxidant enzymes. Antioxidant experiments in vitro showed that DKGM (DP 5.2), obtained by β-mannanase degradation, not only could eliminate hydroxyl radicals (OH) and 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH), but also had great reducing power (Liu J et al., 2015 2015 ). Moreover, cytological tests in human hepatic cells revealed that DKGM (53 kDa) degraded by 100 kGy irradiation not only significantly increased cellular survival and activity of glutathione peroxidase and intracellular activity of catalase, but also reduced the levels of lactate dehydrogenase, malondialdehyde, and intracellular accumulation of reactive oxygen species (ROS), providing a protective effect against oxidative damage by H 2 O 2 (Jian et al., 2017 2017 ). (2) Fermentation products of DKGM produced by bacteria also exert anti-oxidative effects. However, the mechanisms vary depending on its molecular weight and the bacterial strains (Wang et al., 2008 2008 ). Native KGM and DKGM with different DPs within five colonic bacteria were compared. The results suggested that native KGM produces anti-oxidative activity mainly through initiation of ferrous ion-induced peroxidation. Nevertheless, fermentation of DKGM (DP=5) produced anti-oxidative effects by reducing ferrous ion-induced peroxidation and the formation of lipid peroxide products and increasing radical-eliminating ability, whereas fermentation of DKGM (DP=10) produced anti-oxidative effects by increasing radical-scavenging ability and eliminating lipid peroxide formation. Immune activity 2 Administration of DKGM has positive immunomodulatory effects on various animal species, including mammals (Suzuki et al., 2010 2010 ) and fish (Zheng et al., 2015 2015 , 2016 2016 ). Mechanism studies revealed that DKGM at an optimal size (between 10 and 500 kDa) could inhibit the production of immunoglobulin E (IgE) and enhance interferon-γ (IFN-γ) in vitro, thereby easing atopic disease in mice (Suzuki et al., 2010 2010 ). DKGM (4.7×10 5 Da) and low molecular-DKGM (L-KGM; 9.29×10 3 Da), obtained by H 2 O 2 and HCl degradation, were used to evaluate effects on immune response in Schizothorax prenanti . Data suggested that the ideal dosage of L-DKGM for enhancement of the immune system was 8.0 g/kg and that the immunomodulatory mechanism involved a significant enhancement of lysozyme, superoxide dismutase (SOD) activity, and immune factors (1L-1β and TNF-α) and a significant reduction in the malondialdehyde level, leading to better resistance to Aeromonas hydrophila (Zheng et al., 2015 2015 , 2016 2016 ). Conclusions 1 The health benefits of DKGM have been confirmed and accepted. However, most studies have focused mainly on producing DKGM with low molecular weight. In addition, the relation between its physicochemical properties and its health benefits is still unclear. Therefore, further studies focused on DKGM are needed to develop manageable and physiological benefit-oriented technologies to produce DKGM with a specific structure, providing guidelines for industrial product design. References S Albrecht , GC van Muiswinkel , HA Schols , 等 . Introducing capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for the characterization of konjac glucomannan oligosaccharides and their in vitro fermentation behavior . J Agric Food Chem , 2009 . 57 ( 9 ): 3867 - 3876 . 19296676 DOI: 10.1021/jf8038956 http://doi.org/10.1021/jf8038956 . Introducing capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for the characterization of konjac glucomannan oligosaccharides and their in vitro fermentation behavior FH Al-Ghazzewi , RF Tester . Effect of konjac glucomannan hydrolysates and probiotics on the growth of the skin bacterium Propionibacterium acnes in vitro . Int J Cosmet Sci , 2010 . 32 ( 2 ): 139 - 142 . 19818083 DOI: 10.1111/j.1468-2494.2009.00555.x http://doi.org/10.1111/j.1468-2494.2009.00555.x . Effect of konjac glucomannan hydrolysates and probiotics on the growth of the skin bacterium Propionibacterium acnes in vitro FH Al-Ghazzewi , RF Tester . Efficacy of cellulase and mannanase hydrolysates of konjac glucomannan to promote the growth of lactic acid bacteria . J Sci Food Agric , 2012 . 92 ( 11 ): 2394 - 2396 . 22495737 DOI: 10.1002/jsfa.5678 http://doi.org/10.1002/jsfa.5678 . Efficacy of cellulase and mannanase hydrolysates of konjac glucomannan to promote the growth of lactic acid bacteria FH Al-Ghazzewi , S Khanna , RF Tester , 等 . The potential use of hydrolysed konjac glucomannan as a prebiotic . J Sci Food Agric , 2007 . 87 ( 9 ): 1758 - 1766 . DOI: 10.1002/jsfa.2919 http://doi.org/10.1002/jsfa.2919 . The potential use of hydrolysed konjac glucomannan as a prebiotic FH Al-Ghazzewi , RF Tester , K Alvani . The synbiotic effects of konjac glucomannan hydrolysates (GMH) and lactobacilli on the growth of Staphylococcus aureus and Salmonella typhimurium . Nutr Food Sci , 2012 . 42 ( 2 ): 97 - 101 . DOI: 10.1108/00346651211212051 http://doi.org/10.1108/00346651211212051 . The synbiotic effects of konjac glucomannan hydrolysates (GMH) and lactobacilli on the growth of Staphylococcus aureus and Salmonella typhimurium E Bateni , R Tester , F Al-Ghazzewi , 等 . The use of konjac glucomannan hydrolysates (GMH) to improve the health of the skin and reduce acne vulgaris . Am J Dermatol Venereol , 2013 . 2 ( 2 ): 10 - 14 . DOI: 10.5923/j.ajdv.20130202.02 http://doi.org/10.5923/j.ajdv.20130202.02 . The use of konjac glucomannan hydrolysates (GMH) to improve the health of the skin and reduce acne vulgaris SS Behera , RC Ray . Konjac glucomannan, a promising polysaccharide of Amorphophallus konjac K. Koch in health care . Int J Biol Macromol , 2016 . 92 942 - 956 . 27481345 DOI: 10.1016/j.ijbiomac.2016.07.098 http://doi.org/10.1016/j.ijbiomac.2016.07.098 . Konjac glucomannan, a promising polysaccharide of Amorphophallus konjac K. Koch in health care DU Bhotmange , JH Wallenius , RS Singhal , 等 . Enzymatic extraction and characterization of polysaccharide from tuber aestivum . Bioact Carbohydr Diet Fibre , 2017 . 10 1 - 9 . DOI: 10.1016/j.bcdf.2017.02.001 http://doi.org/10.1016/j.bcdf.2017.02.001 . Enzymatic extraction and characterization of polysaccharide from tuber aestivum P Cescutti , C Campa , F Delben , 等 . Structure of the oligomers obtained by enzymatic hydrolysis of the glucomannan produced by the plant Amorphophallus konjac . Carbohydr Res , 2002 . 337 ( 24 ): 2505 - 2511 . 12493237 DOI: 10.1016/S0008-6215(02)00332-4 http://doi.org/10.1016/S0008-6215(02)00332-4 . Structure of the oligomers obtained by enzymatic hydrolysis of the glucomannan produced by the plant Amorphophallus konjac CY Chen , YC Huang , TY Yang , 等 . Degradation of konjac glucomannan by Thermobifida fusca thermostable β-mannanase from yeast transformant . Int J Biol Macromol , 2016 . 82 1 - 6 . 26476245 DOI: 10.1016/j.ijbiomac.2015.10.008 http://doi.org/10.1016/j.ijbiomac.2015.10.008 . Degradation of konjac glucomannan by Thermobifida fusca thermostable β-mannanase from yeast transformant F Chen , H Qian . Optimization of ultrasonic degradation of konjac glucomannan by response surface analysis . Sci Technol Food Ind , 2008 . 29 ( 1 ): 146 - 152 . (in Chinese) . Optimization of ultrasonic degradation of konjac glucomannan by response surface analysis HL Chen , YH Fan , ME Chen , 等 . Unhydrolyzed and hydrolyzed konjac glucomannans modulated cecal and fecal microflora in Balb/c mice . Nutrition , 2005 . 21 ( 10 ): 1059 - 1064 . 16157244 DOI: 10.1016/j.nut.2005.02.008 http://doi.org/10.1016/j.nut.2005.02.008 . Unhydrolyzed and hydrolyzed konjac glucomannans modulated cecal and fecal microflora in Balb/c mice J Chen , D Liu , B Shi , 等 . Optimization of hydrolysis conditions for the production of glucomanno-oligosaccharides from konjac using β-mannanase by response surface methodology . Carbohydr Polym , 2013 . 93 ( 1 ): 81 - 88 . 23465904 DOI: 10.1016/j.carbpol.2012.05.037 http://doi.org/10.1016/j.carbpol.2012.05.037 . Optimization of hydrolysis conditions for the production of glucomanno-oligosaccharides from konjac using β-mannanase by response surface methodology LF Cheng , XY Feng , SW Duan , 等 . Optimization of the process conditions on preparation of glucomanno-oligosaccharides using a novel β-mannanase . Food Sci , 2016 . 37 ( 6 ): 34 - 38 . (in Chinese) DOI: 10.7506/spkx1002-6630-201606006 http://doi.org/10.7506/spkx1002-6630-201606006 . Optimization of the process conditions on preparation of glucomanno-oligosaccharides using a novel β-mannanase ML Connolly , JA Lovegrove , KM Tuohy . Konjac glucomannan hydrolysate beneficially modulates bacterial composition and activity within the faecal microbiota . J Funct Foods , 2010 . 2 ( 3 ): 219 - 224 . DOI: 10.1016/j.jff.2010.05.001 http://doi.org/10.1016/j.jff.2010.05.001 . Konjac glucomannan hydrolysate beneficially modulates bacterial composition and activity within the faecal microbiota Y Dang , SY Liu , ZJ Zhang , 等 . Research of preparation and production optimization of mannoligosaccharides . Sci Technol Food Ind , 2015 . 36 ( 8 ): 250 - 256 . (in Chinese) . Research of preparation and production optimization of mannoligosaccharides LL Deng , G Zhong , BY Liu , 等 . Properties of konjac oligosaccharides prepared by semi-dry enzymatic hydrolysis . Food Sci , 2013 . 34 ( 15 ): 115 - 119 . (in Chinese) DOI: 10.7506/spkx1002-6630-201315024 http://doi.org/10.7506/spkx1002-6630-201315024 . Properties of konjac oligosaccharides prepared by semi-dry enzymatic hydrolysis S Dhawan , J Kaur . Microbial mannanases: an overview of production and applications . Crit Rev Biotechnol , 2007 . 27 ( 4 ): 197 - 216 . 18085462 DOI: 10.1080/07388550701775919 http://doi.org/10.1080/07388550701775919 . Microbial mannanases: an overview of production and applications AA Elamir , RF Tester , FH Al-Ghazzewi , 等 . Effects of konjac glucomannan hydrolysates on the gut microflora of mice . Nutr Food Sci , 2008 . 38 ( 5 ): 422 - 429 . DOI: 10.1108/00346650810906930 http://doi.org/10.1108/00346650810906930 . Effects of konjac glucomannan hydrolysates on the gut microflora of mice L Feng , XJ An , Y Qi , 等 . Protective effect of konjac oligo-glucomannan on trinitrobenzene sulfonic acid-induced ulcerative colitis in mice . Sci Technol Food Ind , 2015 . 36 ( 1 ): 349 - 352 . (in Chinese) . Protective effect of konjac oligo-glucomannan on trinitrobenzene sulfonic acid-induced ulcerative colitis in mice Y Guo , HS Wang , K Zhou . Effect of konjacmannan oligosaccharides on the co-culture of Lactobacillus plantarum and Enterococcus faecalis . Chin Wild Plant Resour , 2017 . 36 ( 2 ): 13 - 16 . (in Chinese) DOI: 10.3969/j.issn.1006-9690.2017.02.004 http://doi.org/10.3969/j.issn.1006-9690.2017.02.004 . Effect of konjacmannan oligosaccharides on the co-culture of Lactobacillus plantarum and Enterococcus faecalis D He , X Guo , SL Yang , 等 . Preparation of konjac mannose-oligosaccharides by β-mannanase and composition analysis . China Brew , 2013 . 32 ( 2 ): 85 - 88 . (in Chinese) . Preparation of konjac mannose-oligosaccharides by β-mannanase and composition analysis YC Huang , QR Xie , YF Ma , 等 . Study on the degradation of konjac glucomannan with ultrasonic . Food Sci Technol , 2006 . ( 9 ): 103 - 105 . (in Chinese) . Study on the degradation of konjac glucomannan with ultrasonic W Jian , Y Sun , H Huang , 等 . Study on preparation and separation of Konjac oligosaccharides . Carbohydr Polym , 2013 . 92 ( 2 ): 1218 - 1224 . 23399149 DOI: 10.1016/j.carbpol.2012.09.065 http://doi.org/10.1016/j.carbpol.2012.09.065 . Study on preparation and separation of Konjac oligosaccharides W Jian , L Tu , L Wu , 等 . Physicochemical properties and cellular protection against oxidation of degraded Konjac glucomannan prepared by γ-irradiation . Food Chem , 2017 . 231 42 - 50 . 28450022 DOI: 10.1016/j.foodchem.2017.03.121 http://doi.org/10.1016/j.foodchem.2017.03.121 . Physicochemical properties and cellular protection against oxidation of degraded Konjac glucomannan prepared by γ-irradiation M Jiang , H Li , M Wang , 等 . Subchronic toxicity and genotoxicity assessment of low molecular mass konjac mannan oligosaccharide in vitro and in vivo . Prog Biochem Biophys , 2016 . 43 ( 3 ): 271 - 280 . (in Chinese) DOI: 10.1647/j.pibb.2015.0313 http://doi.org/10.1647/j.pibb.2015.0313 . Subchronic toxicity and genotoxicity assessment of low molecular mass konjac mannan oligosaccharide in vitro and in vivo F Jiao , X Wang , X Song , 等 . Processing optimization and anti-oxidative activity of enzymatic extractable polysaccharides from Pleurotus djamor . Int J Biol Macromol , 2017 . 98 469 - 478 . 28167111 DOI: 10.1016/j.ijbiomac.2017.01.126 http://doi.org/10.1016/j.ijbiomac.2017.01.126 . Processing optimization and anti-oxidative activity of enzymatic extractable polysaccharides from Pleurotus djamor W Jin , W Xu , Z Li , 等 . Degraded konjac glucomannan by γ-ray irradiation assisted with ethanol: preparation and characterization . Food Hydrocoll , 2014 . 36 85 - 92 . DOI: 10.1016/j.foodhyd.2013.09.005 http://doi.org/10.1016/j.foodhyd.2013.09.005 . Degraded konjac glucomannan by γ-ray irradiation assisted with ethanol: preparation and characterization W Jin , T Mei , Y Wang , 等 . Synergistic degradation of konjac glucomannan by alkaline and thermal method . Carbohydr Polym , 2014 . 99 270 - 277 . 24274506 DOI: 10.1016/j.carbpol.2013.08.029 http://doi.org/10.1016/j.carbpol.2013.08.029 . Synergistic degradation of konjac glucomannan by alkaline and thermal method LX Kang , YL Zhou , LX Ma . Enzymatic preparation of mannose-oligosacchades . Food Sci Technol , 2012 . 37 ( 7 ): 237 - 239 . (in Chinese) . Enzymatic preparation of mannose-oligosacchades J Li , B Li , P Geng , 等 . Ultrasonic degradation kinetics and rheological profiles of a food polysaccharide (konjac glucomannan) in water . Food Hydrocoll , 2017 . 70 14 - 19 . DOI: 10.1016/j.foodhyd.2017.03.022 http://doi.org/10.1016/j.foodhyd.2017.03.022 . Ultrasonic degradation kinetics and rheological profiles of a food polysaccharide (konjac glucomannan) in water JF Li , MC Wu , K Cheng , 等 . Study on the preparation of oligo-glucomannan using konjak gum by β-mannanase . Food Ferment Ind , 2007 . 33 ( 1 ): 21 - 24 . (in Chinese) . Study on the preparation of oligo-glucomannan using konjak gum by β-mannanase MY Li , GP Feng , ZL Xu , 等 . Effect of γ irradiation on the prebiotic functions of konjac glucomannan . Food Sci , 2018 . 39 ( 11 ): 83 - 88 . DOI: 10.7506/spkx1002-6630-201811013 http://doi.org/10.7506/spkx1002-6630-201811013 . Effect of γ irradiation on the prebiotic functions of konjac glucomannan HX Liu , JS Gong , H Li , 等 . Biochemical characterization and cloning of an endo-1,4-β-mannanase from Bacillus subtilis YH12 with unusually broad substrate profile . Process Biochem , 2015 . 50 ( 5 ): 712 - 721 . DOI: 10.1016/j.procbio.2015.02.011 http://doi.org/10.1016/j.procbio.2015.02.011 . Biochemical characterization and cloning of an endo-1,4-β-mannanase from Bacillus subtilis YH12 with unusually broad substrate profile J Liu , Q Xu , J Zhang , 等 . Preparation, composition analysis and antioxidant activities of konjac oligo-glucomannan . Carbohydr Polym , 2015 . 130 398 - 404 . 26076641 DOI: 10.1016/j.carbpol.2015.05.025 http://doi.org/10.1016/j.carbpol.2015.05.025 . Preparation, composition analysis and antioxidant activities of konjac oligo-glucomannan R Liu , Y Li , B Zhang . The effects of konjac oligosaccharide on TNBS-induced colitis in rats . Int Immunopharmacol , 2016 . 40 385 - 391 . 27694039 DOI: 10.1016/j.intimp.2016.08.040 http://doi.org/10.1016/j.intimp.2016.08.040 . The effects of konjac oligosaccharide on TNBS-induced colitis in rats RX Liu , YC Li , B Zhang . Effect of konja coligosaccharide on gut microbiota in rats with ulcerative colitis . J Chin Instit Food Sci Technol , 2017 . 17 ( 6 ): 53 - 59 . (in Chinese) . Effect of konja coligosaccharide on gut microbiota in rats with ulcerative colitis A Mikkelson , H Maaheimo , TK Hakala . Hydrolysis of konjac glucomannan by Trichoderma reesei mannanase and endoglucanases Cel7B and Cel5A for the production of glucomannooligosaccharides . Carbohydr Res , 2013 . 372 60 - 68 . 23537778 DOI: 10.1016/j.carres.2013.02.012 http://doi.org/10.1016/j.carres.2013.02.012 . Hydrolysis of konjac glucomannan by Trichoderma reesei mannanase and endoglucanases Cel7B and Cel5A for the production of glucomannooligosaccharides T Pan , S Peng , Z Xu , 等 . Synergetic degradation of konjac glucomannan by γ-ray irradiation and hydrogen peroxide . Carbohydr Polym , 2013 . 93 ( 2 ): 761 - 767 . 23499121 DOI: 10.1016/j.carbpol.2012.11.075 http://doi.org/10.1016/j.carbpol.2012.11.075 . Synergetic degradation of konjac glucomannan by γ-ray irradiation and hydrogen peroxide M Primec , D Mičetić-Turk , T Langerholc . Analysis of short-chain fatty acids in human feces: a scoping review . Anal Biochem , 2017 . 526 9 - 21 . 28300535 DOI: 10.1016/j.ab.2017.03.007 http://doi.org/10.1016/j.ab.2017.03.007 . Analysis of short-chain fatty acids in human feces: a scoping review QJ Qin , Y Zhang , BY Liu , 等 . Optimization of the preparation of konjac oligo-glucomannan in semi-drying enzymatic hydrolysis method and its antioxidant capacity . Sci Tech Food Ind , 2013 . 34 ( 23 ): 186 - 191 . (in Chinese) . Optimization of the preparation of konjac oligo-glucomannan in semi-drying enzymatic hydrolysis method and its antioxidant capacity QJ Qin , XQ Xu , Y Zhang , 等 . Toxicological and prebiotic evaluation of konjac oligosaccharides . Food Sci , 2014 . 35 ( 21 ): 244 - 248 . (in Chinese) DOI: 10.7506/spkx1002-6630-201421048 http://doi.org/10.7506/spkx1002-6630-201421048 . Toxicological and prebiotic evaluation of konjac oligosaccharides S Sivaprakasam , PD Prasad , N Singh . Benefits of short-chain fatty acids and their receptors in inflammation and carcinogenesis . Pharmacol Ther , 2016 . 164 144 - 151 . 27113407 DOI: 10.1016/j.pharmthera.2016.04.007 http://doi.org/10.1016/j.pharmthera.2016.04.007 . Benefits of short-chain fatty acids and their receptors in inflammation and carcinogenesis P Suwannaporn , K Thepwong , R Tester , 等 . Tolerance and nutritional therapy of dietary fibre from konjac glucomannan hydrolysates for patients with inflammatory bowel disease (IBD) . Bioact Carbohydr Diet Fibre , 2013 . 2 ( 2 ): 93 - 98 . DOI: 10.1016/j.bcdf.2013.09.005 http://doi.org/10.1016/j.bcdf.2013.09.005 . Tolerance and nutritional therapy of dietary fibre from konjac glucomannan hydrolysates for patients with inflammatory bowel disease (IBD) H Suzuki , S Oomizu , Y Yanase , 等 . Hydrolyzed konjac glucomannan suppresses IgE production in mice B cells . Int Arch Allergy Immumol , 2010 . 152 ( 2 ): 122 - 130 . DOI: 10.1159/000265533 http://doi.org/10.1159/000265533 . Hydrolyzed konjac glucomannan suppresses IgE production in mice B cells JH Tao , JA Duan , S Jiang , 等 . Simultaneous determination of six short-chain fatty acids in colonic contents of colitis mice after oral administration of polysaccharides from Chrysanthemum morifolium Ramat by gas chromatography with flame ionization detector . J Chromatogr B Analyt Technol Biomed Life Sci , 2016 . 1029 ( 2 ): 88 - 94 . DOI: 10.1016/j.jchromb.2016.07.002 http://doi.org/10.1016/j.jchromb.2016.07.002 . Simultaneous determination of six short-chain fatty acids in colonic contents of colitis mice after oral administration of polysaccharides from Chrysanthemum morifolium Ramat by gas chromatography with flame ionization detector R Tester , F Al-Ghazzewi . Glucomannans and nutrition . Food Hydrocoll , 2017 . 68 246 - 254 . DOI: 10.1016/j.foodhyd.2016.05.017 http://doi.org/10.1016/j.foodhyd.2016.05.017 . Glucomannans and nutrition R Tester , F Al-Ghazzewi , N Shen . The use of konjac glucomannan hydrolysates to recover healthy microbiota in infected vaginas treated with an antifungal agent . Benef Microbes , 2012 . 3 ( 1 ): 61 - 66 . DOI: 10.3920/BM2011.0021 http://doi.org/10.3920/BM2011.0021 . The use of konjac glucomannan hydrolysates to recover healthy microbiota in infected vaginas treated with an antifungal agent MM Unger , J Spiegel , KU Dillmann , 等 . Short chain fatty acids and gut microbiota differ between patients with Parkinson’s disease and age-matched controls . Parkinsonism Relat Disord , 2016 . 32 66 - 72 . DOI: 10.1016/j.parkreldis.2016.08.019 http://doi.org/10.1016/j.parkreldis.2016.08.019 . Short chain fatty acids and gut microbiota differ between patients with Parkinson’s disease and age-matched controls WH van Zyl , SH Rose , K Trollope , 等 . Fungal β-mannanases: mannan hydrolysis, heterologous production and biotechnological applications . Process Biochem , 2010 . 45 ( 8 ): 1203 - 1213 . DOI: 10.1016/j.procbio.2010.05.011 http://doi.org/10.1016/j.procbio.2010.05.011 . Fungal β-mannanases: mannan hydrolysis, heterologous production and biotechnological applications JJ Wan , M Jiang , H Li , 等 . Effects of low polymerization degree konjacmannan-oligosaccharide on intestinal and microflora of normal mice . Food Ferment Ind , 2015 . 41 ( 9 ): 13 - 18 . (in Chinese) . Effects of low polymerization degree konjacmannan-oligosaccharide on intestinal and microflora of normal mice CH Wang , P Lai , ME Chen , 等 . Antioxidative capacity produced by Bifidobacteriu m-and Lactobacillus acidophilus-mediated fermentations of konjac glucomannan and glucomannan oligosaccharides . J Sci Food Agric , 2008 . 88 ( 7 ): 1294 - 1300 . DOI: 10.1002/jsfa.3226 http://doi.org/10.1002/jsfa.3226 . Antioxidative capacity produced by Bifidobacterium-and Lactobacillus acidophilus-mediated fermentations of konjac glucomannan and glucomannan oligosaccharides L Wang , SS Tan , R Song , 等 . Synergistic effect of konjac oligosaccharides/isomalto-oligosaccharide complex on the growth of Lactobacillus acidophilus . Mod Food Sci Technol , 2015 . 31 ( 10 ): 151 - 155 . (in Chinese) . Synergistic effect of konjac oligosaccharides/isomalto-oligosaccharide complex on the growth of Lactobacillus acidophilus M Wang , TG Shuai , QJ Qin , 等 . Effect of konjac oligosaccharides on rat intestinal environment . Food Sci , 2016 . 37 ( 7 ): 197 - 203 . (in Chinese) DOI: 10.7506/spkx1002-6630-201607036 http://doi.org/10.7506/spkx1002-6630-201607036 . Effect of konjac oligosaccharides on rat intestinal environment M Wang , M Jiang , H Li , 等 . Investigation on the regular patterns of mannan oligosaccharides degradation and utilization by lactic acid bacteria . Food Ferment Ind , 2016 . 42 ( 11 ): 20 - 24 . (in Chinese) DOI: 10.13995/j.cnki.11-1802/ts.201611004 http://doi.org/10.13995/j.cnki.11-1802/ts.201611004 . Investigation on the regular patterns of mannan oligosaccharides degradation and utilization by lactic acid bacteria CF Wu , YY Dong , JJ Li , 等 . Study on the preparation of konjac oligo-glucomannan by β-mannanase . 2010 . Biotechnol Bull . ( 1 ): 118 - 122 . (in Chinese) . Study on the preparation of konjac oligo-glucomannan by β-mannanase CM Xu , MC Wu , JF Li , 等 . Study on hydrolytic conditions of konjak glucomannan by β-mannanase . J Food Sci Biotechnol , 2008 . 27 ( 3 ): 120 - 124 . (in Chinese) . Study on hydrolytic conditions of konjak glucomannan by β-mannanase LP Xu , ZY Wu , FX Ren , 等 . Study on the optimization of the enzymatic hydrolysis conditions of konjac gum . J Anhui Agric Sci , 2011 . 39 ( 21 ): 13058 - 13059 . (in Chinese) DOI: 10.3969/j.issn.0517-6611.2011.21.151 http://doi.org/10.3969/j.issn.0517-6611.2011.21.151 . Study on the optimization of the enzymatic hydrolysis conditions of konjac gum MD Xu , L Ke , Q Zeng , 等 . Investigated production of mannan-oligosaccharides using konjac power by β-mannan mannohydrolase from Aspergillus niger . Acta Agric Boreali-Occidentalis Sin , 2005 . 14 ( 6 ): 115 - 118 . (in Chinese) DOI: 10.3969/j.issn.1004-1389.2005.06.027 http://doi.org/10.3969/j.issn.1004-1389.2005.06.027 . Investigated production of mannan-oligosaccharides using konjac power by β-mannan mannohydrolase from Aspergillus niger SC Xu , YL Li , Y Liu , 等 . Study on the preparation of feeding oligo-glucomannan by enzymatic method . Feed Ind , 2011 . 32 ( 2 ): 47 - 49 . (in Chinese) . Study on the preparation of feeding oligo-glucomannan by enzymatic method ZL Xu , YM Sun , YH Yang , 等 . Effect of γ-irradiation on some physiochemical properties of konjac glucomannan . Carbohydr Polym , 2007 . 70 ( 4 ): 444 - 450 . DOI: 10.1016/j.carbpol.2007.05.011 http://doi.org/10.1016/j.carbpol.2007.05.011 . Effect of γ-irradiation on some physiochemical properties of konjac glucomannan J Yang , N Vittori , W Wang , 等 . Molecular weight distribution and fermentation of mechanically pre-treated konjac enzymatic hydrolysates . Carbohydr Polym , 2017 . 159 58 - 65 . 28038754 DOI: 10.1016/j.carbpol.2016.12.014 http://doi.org/10.1016/j.carbpol.2016.12.014 . Molecular weight distribution and fermentation of mechanically pre-treated konjac enzymatic hydrolysates X Yao , XG Luo , BC Han . Study on the enzyme-catalyzed degradation of konjac glucomannan and the preparation conditions on the degradation product of various molecular weights . Sci Tech Food Ind , 2011 . 32 ( 9 ): 97 - 101 . (in Chinese) . Study on the enzyme-catalyzed degradation of konjac glucomannan and the preparation conditions on the degradation product of various molecular weights YQ Zhang , X Gan , BJ Xie . Preparation of konjac oligo-glucomannan by cellulase . J Jinshou Univ (Nat Sci Ed) , 2003 . 3 42 - 44 . (in Chinese) . Preparation of konjac oligo-glucomannan by cellulase ZS Zhang , XM Wang , CB Liu , 等 . The degradation, antioxidant and antimutagenic activity of the mucilage polysaccharide from Dioscorea opposita . Carbohydr Polym , 2016 . 150 227 - 231 . 27312633 DOI: 10.1016/j.carbpol.2016.05.034 http://doi.org/10.1016/j.carbpol.2016.05.034 . The degradation, antioxidant and antimutagenic activity of the mucilage polysaccharide from Dioscorea opposita Q Zheng , Y Wu , H Xu , 等 . The effects of dietary oxidized konjac glucomannan and its acidolysis products on the immune response, expression of immune related genes and disease resistance of Schizothorax prenanti . Fish Shellfish Immunol , 2015 . 45 ( 2 ): 551 - 559 . 25989625 DOI: 10.1016/j.fsi.2015.05.016 http://doi.org/10.1016/j.fsi.2015.05.016 . The effects of dietary oxidized konjac glucomannan and its acidolysis products on the immune response, expression of immune related genes and disease resistance of Schizothorax prenanti Q Zheng , Y Wu , H Xu , 等 . Immune responses to Aeromonas hydrophila infection in Schizothorax prenanti fed with oxidized konjac glucomannan and its acidolysis product . Fish Shellfish Immunol , 2016 . 49 260 - 267 . 26748343 DOI: 10.1016/j.fsi.2015.12.042 http://doi.org/10.1016/j.fsi.2015.12.042 . Immune responses to Aeromonas hydrophila infection in Schizothorax prenanti fed with oxidized konjac glucomannan and its acidolysis product Compliance with ethics guidelines Min JIANG, Heng LI, Jin-song SHI, and Zheng-hong XU declare that they have no conflict of interest. This article does not contain any studies with human or animal subjects performed by any of the authors. 10.1631/jzus.B1700310 Project supported by the National First-Class Discipline Program of Light Industry Technology and Engineering (Nos. LITE2018-18 and LITE2018-11) of China, the Transformation Project for Major Scientific and Technological Achievements in Jiangsu Province (No. BA2015006), the Industry-Academia Cooperation Innovation Fund Project of Jiangsu Province (No. BY2016022-19), and the National Key Technologies R&D Program of China for the 12th Five-year Plan (No. 2012BAD33B06) 2017-06-15 2017-11-20 2022-01-05 Copyright © Zhejiang University and Springer-Verlag GmbH Germany, part of Springer Nature 2018 2018 Journal of Zhejiang University-SCIENCE B (Biomedicine and Biotechnology) 07 19