Production of mannooligosaccharides from various mannans and evaluation of their prebiotic potential

Date nawah powder as a promising waste for β-mannanase production from a new isolate Aspergillus niger MSSFW, statistically improving production and enzymatic characterization

β-Mannanase producing fungus was isolated from coffee powder waste and identified as Aspergillus niger MSSFW (Gen Bank accession number OR668928). Dates nawah powder as industrial and agricultural waste was the most inducer of β-mannanase production. The Plackett-Burman and Central Composite designs were used to improve β-mannanase titer. Optimization studies enhanced the enzyme yield with approximate 13.50-times. β-Mannanase was purified by Sephadex G-150 gel filtration column and the molecular weight was estimated to be 60 kDa by SDS-PAGE. Crude and purified β-mannanase displayed maximum activity at temperature 60 °C and 50 °C, respectively. Crude β-mannanase showed an activation energy value 2.35-times higher than the purified enzyme. Activation energy for thermal denaturation of the purified β-mannanase was 1.08-times higher than that of the crude enzyme. Purified β-mannanase exhibited higher deactivation rate constant (Kd) and lower half-life (t0.5) and decimal reduction time (D-value) compared with the crude enzyme. Thermodynamic parameters of enthalpy, entropy, and free energy values for crude and purified β-mannanase were calculated. Substrate kinetic parameters suggested that the purified β-mannanase had a strong affinity toward locust bean gum by showing 3.44-times lower Km and 1.99-times higher Vmax compared to the crude enzyme.

Value creation of copra meal mannan into functional manno-oligosaccharides (β-MOS) using the mannanase Bacillus man B (BlMan26B)

Agricultural wastes rich in β-mannan are an important environmental problem in tropical and sub-tropical countries. This research aims at dealing with this and investigates the valorization of mannan-rich copra meal from virgin coconut oil manufacturing into mannan-oligosaccharides (β-MOS) by enzymatic hydrolysis using β-mannanase from Bacillus licheniformis (BlMan26B). Lab-scale process, involving pre-treatment and bioconversion steps, were conducted and evaluated. Lyophilized β-MOS was analyzed and its biological activities were assessed. The size of oligosaccharides obtained ranged from dimers to hexamers with 36.7% conversion yields. The prebiotic effects of β-MOS were demonstrated in comparison with commercial inulin and fructo-oligosaccharides (FOS). In vitro toxicity assays of β -MOS on human dermal fibroblasts and monocytes showed no cytotoxic effect. Interestingly, β-MOS at concentrations ranging from 10 to 200 µg/mL also demonstrated potent anti-inflammatory activity against LPS-induced inflammation of human macrophage THP-1 in a dose-dependent manner. However, at high dose, β-MOS could also stimulate inflammation. Therefore, further investigation must be conducted to ensure its efficacy and safe use in the future. These results indicate that β-MOS have the potential to be used as valued-added health-promoting nutraceutical or feed additive after additional in-depth studies. These finding should be applicable for other agricultural wastes rich in mannan as well.

Optimized production and characterization of endo-β-mannanase by Aspergillus niger for generation of prebiotic mannooligosaccharides from guar gum

Optimized production of Aspergillus niger ATCC 26011 endo-β-mannanase (ManAn) on copra meal resulted in 2.46-fold increase (10,028 U/gds). Purified ManAn (47 kDa) showed high affinity towards guar gum (GG) as compared to konjac gum and locust bean gum with Km 2.67, 3.25 and 4.07 mg/mL, respectively. ManAn efficiently hydrolyzed GG and liberated mannooligosaccharides (MOS). Changes occurring in the rheological and compositional aspects of GG studied using Differential scanning calorimetry (DSC), Thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) revealed increased thermal stability and crystallinity of the partially hydrolyzed guar gum (PHGG). Parametric optimization of the time and temperature dependent hydrolysis of GG (1% w/v) with 100 U/mL of ManAn at 60 °C and pH: 5.0 resulted in 12.126 mg/mL of mannotetraose (M4) in 5 min. Enhanced growth of probiotics Lactobacilli and production of short chain fatty acids (SCFA) that inhibited enteropathogens, confirmed the prebiotic potential of PHGG and M4.

Mannooligosaccharide production from açaí seeds by enzymatic hydrolysis: optimization through response surface methodology

Recognized for its bioactive compounds, açaí has become a functional food, but it has a low pulp yield, and the seeds are the main waste. This study investigates the potential of açaí seeds (Euterpe oleracea Mart.) to produce mannooligosaccharides (MOS) through enzymatic hydrolysis. Using response surface methodology (RSM), the research optimizes MOS extraction while minimizing mannose production and reducing processing time, achieving MOS production of about 10 g/L, a value within the range of similar investigations. The RSM quadratic models establish correlations between MOS production (M2-M5) and enzymatic hydrolysis conditions, with R2 values ranging from 0.6136 to 0.9031. These models are used to emphasize MOS performance (M2-M5) while reducing mannose production, which also promotes profitability by reducing time. Experimental validation agrees with model predictions, highlighting optimal conditions near 40 °C, intermediate enzyme loading, and basic pH that effectively promotes MOS generation on mannose within an accelerated processing time frame. With predictions of experimental results within a margin of error of < 9%, the validity of the models was acceptable. This research contributes to the advancement of the understanding of the enzymatic hydrolysis of açaí seeds, which is a step toward the sustainable use of resources with a focus on process engineering aspects.

A Comparative Study of Composition and Soluble Polysaccharide Content between Brewer's Spent Yeast and Cultured Yeast Cells

Yeast, crucial in beer production, holds great potential owing to its ability to transform into a valuable by-product resource, known as brewer's spent yeast (BSY), with potentially beneficial physiological effects. This study aimed to compare the composition and soluble polysaccharide content of Brewer's spent yeast with those of cultured yeast strains, namely Saccharomyces cerevisiae (SC) and S. boulardii (SB), to facilitate the utilization of BSY as an alternative source of functional polysaccharides. BSY exhibited significantly higher carbohydrate content and lower crude protein content than SC and SB cells. The residues recovered through autolysis were 53.11%, 43.83%, and 44.99% for BSY, SC, and SB, respectively. Notably, the polysaccharide content of the BSY residue (641.90 μg/mg) was higher than that of SC (553.52 μg/mg) and SB (591.56 μg/mg). The yields of alkali-extracted water-soluble polysaccharides were 33.62%, 40.76%, and 42.97% for BSY, SC, and SB, respectively, with BSY comprising a comparable proportion of water-soluble saccharides made with SC and SB, including 49.31% mannan and 20.18% β-glucan. Furthermore, BSY demonstrated antioxidant activities, including superoxide dismutase (SOD), ABTS, and DPPH scavenging potential, suggesting its ability to mitigate oxidative stress. BSY also exhibited a significantly higher total phenolic compound content, indicating its potential to act as an effective functional food material.

Characteristics of exopolysaccharides from Paecilomyces hepiali and their simulated digestion and fermentation in vitro by human intestinal microbiota

The metabolic process of polysaccharides in gastrointestinal digestions and the effects of the resulting carbohydrates on the composition of gut microbes are important to explore their prebiotic properties. Therefore, the purpose of this study was to investigate the simulated digestion and fecal fermentation in vitro of three fractions (PHEPSs-1, PHEPSs-2 and PHEPSs-3) purified from the crude exopolysaccharides of Paecilomyces hepiali HN1 (PHEPSs) and to explore the potential prebiotic mechanisms. The three purified fractions were characterized by HPLC, UV, FT-IR, SEM and AFM, and they were all of galactoglucomannan family with molecular weight of 178, 232 and 119 kDa, respectively. They could resist the simulated gastrointestinal digestions, but they were metabolized in fecal fermentation in vitro. Furthermore, the mannose in PHEPSs showed a higher utilization rate than that of glucose or galactose. The proliferation effects of PHEPSs on Bifidobacterium and Lactobacillus were weaker significantly than those of fructooligosaccharides before 12 h of fecal fermentation, but stronger after 24 h of fecal fermentation. Meanwhile, higher levels of short-chain fatty acids were found in PHEPSs groups when the fecal fermentation extended to 36 h. Therefore, PHEPSs are expected to have a potent gut healthy activity and can be explored as functional food ingredients.

Material basis and core chemical structure of Dendrobium officinale polysaccharides against colitis-associated cancer based on anti-inflammatory activity

It has been claimed that Dendrobium officinale polysaccharides (PSs) can degrade into oligosaccharide and then transform into short-chain fatty acids in the intestine after oral administration, and play an anti-colitis-associated cancer (CAC) effect by inhibiting intestinal inflammation. However, the material basis and core chemical structure underlying the anti-colon cancer properties of PSs have not yet been elucidated. In this study, PSs were degraded into enzymatic oligosaccharides (OSs) using β-mannanase. The results of in vivo experiments revealed that PSs and OSs administered by gastric lavage had similar antitumor effects in CAC mice. OS-1 (Oligosaccharide compounds 1) and OS-2 (Oligosaccharide compounds 2) were further purified and characterized from OSs, and it was found that OS-1, OS-2, OSs, and PSs had similar and consistent anti-inflammatory activities in vitro. Chemical structure comparison and evaluation revealed that the chemical structure of β-D-Manp-(1 → 4)-β-D-Glcp corresponding to OS-1 was the least common PS structure with anti-colitic activity. Therefore, our findings suggest that OSs are the material basis for PSs to exert anti-CAC activity and that the chemical structure of β-D-Manp-(1 → 4)-β-D-Glcp corresponding to OS-1 is the core chemical structure of PSs against CAC.

Enhanced Enzymatic Performance of β-Mannanase Immobilized on Calcium Alginate Beads for the Generation of Mannan Oligosaccharides

Mannan oligosaccharides (MOSs) are excellent prebiotics that are usually obtained via the enzymatic hydrolysis of mannan. In order to reduce the cost of preparing MOSs, immobilized enzymes that demonstrate good performance, require simple preparation, and are safe, inexpensive, and reusable must be developed urgently. In this study, β-mannanase was immobilized on calcium alginate (CaAlg). Under the optimal conditions of 320 U enzyme addition, 1.6% sodium alginate, 2% CaCl2, and 1 h of immobilization time, the immobilization yield reached 68.3%. The optimum temperature and pH for the immobilized β-mannanase (Man-CaAlg) were 75 °C and 6.0, respectively. The Man-CaAlg exhibited better thermal stability, a high degree of pH stability, and less substrate affinity than free β-mannanase. The Man-CaAlg could be reused eight times and retained 70.34% of its activity; additionally, the Man-CaAlg showed 58.17% activity after 30 days of storage. A total of 7.94 mg/mL of MOSs, with 4.94 mg/mL of mannobiose and 3.00 mg/mL of mannotriose, were generated in the oligosaccharide production assay. It is believed that this convenient and safe strategy has great potential in the important field of the use of immobilized β-mannanase for the production of mannan oligosaccharides.

Digestibility and Palatability of the Diet and Intestinal Functionality of Dogs Fed a Blend of Yeast Cell Wall and Oregano Essential Oil

Feed additives, such as prebiotics and essential oils, are used in pet foods and can affect digestibility, palatability, and intestinal functionality of dogs. The combined effects of yeast cell wall and oregano essential oil on apparent total tract digestibility (ATTD) and palatability of diet, intestinal fermentation products, and fecal microbiota in dogs were analyzed. Eighteen adult dogs were fed for 20 days with three dry extruded diets for adult dogs: control (without the additive), a diet containing 1.5 kg/ton of yeast cell wall and oregano essential oil (1.5YCO), and a diet containing 3.0 kg/ton of yeast cell wall and oregano essential oil (3.0YCO). The inclusion of both levels of YCO reduced the intake ratio. The addition of 3.0YCO reduced the ATTD of dry matter, compared to the control group (p < 0.05). There were greater putrescine and cadaverine concentrations and lower histamine and ammonia (p < 0.05) in the feces of dogs fed 3.0YCO. In addition, fecal odor of dogs fed YCO was less fetid than the control group (p < 0.05). There was greater fecal bacterial diversity in dogs fed with both dietary concentrations of YCO evaluated (p < 0.05). Dogs fed 1.5YCO and 3.0YCO showed higher relative abundance of Blautia and Faecalibacterium and lower abundance of Streptococcus (p < 0.05) in the feces, in comparison to the control group. Given the modulation of microorganisms considered beneficial and the lower fecal concentrations of histamine, phenols, and ammonia, the YCO blend resulted in indicators of improvement of intestinal functionality in dogs.

Hybridization altered the gut microbiota of pigs

Mammalian gut microbiota plays an important role in the host's nutrient metabolism, growth, and immune regulation. Hybridization can enable a progeny to acquire superior traits of the parents, resulting in the hybridization advantage. However, studies on the effects of hybridization on the pigs' gut microbiota are lacking. Therefore, this study used multi-omics technologies to compare and analyze the gut microbiota of the primary wild boar and its offspring. The 16S rRNA gene sequencing results revealed that the gut microbiota of F4 exhibited a host-like dominance phenomenon with a significant increase in the abundance of Lactobacillus and Bifidobacterium. The beta diversity of Duroc was significantly different from those of F0, F2, and F4; after the host hybridization, the similarity of the beta diversity in the progeny decreased with the decrease in the similarity of the F0 lineage. The metagenomic sequencing results showed that the significantly enriched metabolic pathways in F4, such as environmental, circulatory system, fatty acid degradation adaptation, and fatty acid biosynthesis, were similar to those in F0. Moreover, it also exhibited similar significantly enriched metabolic pathways as those in Duroc, such as carbohydrate metabolism, starch and sucrose metabolism, starch-degrading CAZymes, lactose-degrading CAZymes, and various amino acid metabolism pathways. However, the alpha-amylase-related KOs, lipid metabolism, and galactose metabolism in F4 were significantly higher than those in Duroc and F0. Non-targeted metabolome technology analysis found that several metabolites, such as docosahexaenoic acid, arachidonic acid, and citric acid were significantly enriched in the F4 pigs as compared to those in F0. Based on Spearman correlation analysis, Lactobacillus and Bifidobacterium were significantly positively correlated with these metabolites. Finally, the combined metagenomic and metabolomic analysis suggested that the metabolic pathways, such as valine, leucine, and isoleucine biosynthesis and alanine aspartate and glutamate metabolism were significantly enriched in F4 pigs. In conclusion, the gut microbiota of F4 showed a similar host "dominance" phenomenon, which provided reference data for the genetics and evolution of microbiota and the theory of microbial-assisted breeding.

Functional β-mannooligosaccharides: Sources, enzymatic production and application as prebiotics

One of the emerging non-digestible oligosaccharide prebiotics is β-mannooligosaccharides (β-MOS). β-MOS are β-mannan derived oligosaccharides, they are selectively fermented by gut microbiota, promoting the growth of beneficial microorganisms (probiotics), whereas the growth of enteric pathogens remains unaffected or gets inhibited in their presence, along with production of metabolites such as short-chain fatty acids. β-MOS also exhibit several other bioactive properties and health-promoting effects. Production of β-MOS using the enzymes such as β-mannanases is the most effective and eco-friendly approach. For the application of β-MOS on a large scale, their production needs to be standardized using low-cost substrates, efficient enzymes and optimization of the production conditions. Moreover, for their application, detailed in-vivo and clinical studies are required. For this, a thorough information of various studies in this regard is needed. The current review provides a comprehensive account of the enzymatic production of β-MOS along with an evaluation of their prebiotic and other bioactive properties. Their characterization, structural-functional relationship and in-vivo studies have also been summarized. Research gaps and future prospects have also been discussed, which will help in conducting further research for the commercialization of β-MOS as prebiotics, functional food ingredients and therapeutic agents.

Biochemical analyses of a novel acidophilic GH5 β-mannanase from Trichoderma asperellum ND-1 and its application in mannooligosaccharides production from galactomannans

In this study, an acidophilic GH5 β-mannanase (TaMan5) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 2.0-fold increase, 67.5 ± 1.95 U/mL). TaMan5 displayed the highest specificity toward locust bean gum (K_m = 1.34 mg/mL, V_max = 749.14 μmol/min/mg) at pH 4.0 and 65°C. Furthermore, TaMan5 displayed remarkable tolerance to acidic environments, retaining over 80% of its original activity at pH 3.0-5.0. The activity of TaMan5 was remarkably decreased by Cu²⁺, Mn²⁺, and SDS, while Fe²⁺/Fe³⁺ improved the enzyme activity. A thin-layer chromatography (TLC) analysis of the action model showed that TaMan5 could rapidly degrade mannan/MOS into mannobiose without mannose via hydrolysis action as well as transglycosylation. Site-directed mutagenesis results suggested that Glu²⁰⁵, Glu³¹³, and Asp³⁵⁷ of TaMan5 are crucial catalytic residues, with Asp¹⁵² playing an auxiliary function. Additionally, TaMan5 and commercial α-galactosidase displayed a remarkable synergistic effect on the degradation of galactomannans. This study provided a novel β-mannanase with ideal characteristics and can be considered a potential candidate for the production of bioactive polysaccharide mannobiose.

Heterologous Expression, Purification and Characterization of an Alkalic Thermophilic β-Mannanase CcMan5C from Coprinopsis cinerea

A endo-1,4-β-mannanase (CcMan5C) gene was cloned from Coprinopsis cinerea and heterologously expressed in Pichia pastoris, and the recombinant enzyme was purified by Ni-affinity chromatography and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). CcMan5C hydrolyzed only locust bean gum galactomannan (LBG) but not α-mannan from S. cerevisiae or Avicel cellulose, oat spelt xylan, or laminarin from Laminaria digitata. CcMan5C exhibited distinctive catalytic features that were different from previously reported β-mannanases. (1) CcMan5C is the first reported fungal β-mannase with an optimal alkalic pH of 8.0-9.0 for hydrolytic activity under assay conditions. (2) CcMan5C is the first reported alkalic fungal β-mannase with an optimal temperature of 70 °C for hydrolytic activity under assay conditions. (3) The organic solvents methanol, ethanol, isopropanol, and acetone at concentrations of 10% or 20% did not inhibit CcMan5C activity, while 10% or 20% isopropanol and acetone even enhanced CcMan5C activity by 9.20-34.98%. Furthermore, CcMan5C tolerated detergents such as Tween 20 and Triton X-100, and its activity was even enhanced to 26.2-45.6% by 1% or 10% Tween 20 and Triton X-100. (4) CcMan5C solution or lyophilized CcMan5C exhibited unchanged activity and even increasing activity after being stored at -20 °C or -80 °C for 12 months and retained above 50% activity after being stored at 4 °C for 12 months. These features make CcMan5C a suitable candidate for the detergent industry and paper and pulp industry.

Thermostability modification of β-mannanase from Aspergillus niger via flexibility modification engineering

Introduction

β-Mannanases can hydrolyze mannans, which are widely available in nature. However, the optimum temperature of most β-mannanases is too low to be directly utilized in industry.

Methods

To further improve the thermostability of Anman (mannanase from Aspergillus niger CBS513.88), B-factor and Gibbs unfolding free energy change were used to modify the flexible of Anman, and then combined with multiple sequence alignment and consensus mutation to generate an excellent mutant. At last, we analyzed the intermolecular forces between Anman and the mutant by molecular dynamics simulation.

Results

The thermostability of combined mutant mut5 (E15C/S65P/A84P/A195P/T298P) was increased by 70% than the wild-type Amman at 70°C, and the melting temperature (Tm) and half-life (t1/2) values were increased by 2°C and 7.8-folds, respectively. Molecular dynamics simulation showed reduced flexibility and additional chemical bonds in the region near the mutation site.

Discussion

These results indicate that we obtained a Anman mutant that is more suitable for industrial application, and they also confirm that a combination of rational and semi-rational techniques is helpful for screening mutant sites.

Molecular insight into Aspergillus oryzae β-mannanase interacting with mannotriose revealed by molecular dynamic simulation study

Fungal β-mannanases hydrolyze β-1, 4-glycosidic bonds of mannans and find application in the generation of mannose and prebiotic mannooligosaccharides (MOS). Previously, a MOS generating β-mannanase from Aspergillus oryzae MTCC 1846 (βManAo) was characterized and its structural and functional properties were unraveled through homology modeling and molecular dynamics in this study. The βManAo model was validated with 92.9% and 6.5% of the residues found to be distributed in the most favorable and allowed regions of the Ramachandran plot. Glu244 was found to play a key role in the interaction with mannotriose, indicating conserved amino acids for the catalytic reaction. A detailed metadynamic analysis of the principal components revealed the presence of an α₈-helix in the C-terminus which was very flexible in nature and energy landscapes suggested high conformation sub-states and the complex dynamic behavior of the protein. The binding of the M3 substrate stabilized the β-mannanase and resulted in a reduction in the intermediate conformational sub-states evident from the free energy landscapes. The active site of the β-mannanase is mostly hydrophilic in nature which is accordance with our results, where the major contribution in the binding energy of the substrate with the active site is from electrostatic interactions. Define Secondary Structure of Proteins (DSSP) analysis revealed a major transition of the protein from helix to β-turn for binding with the mannotriose. The molecular dynamics of the βManAo–mannotriose model, and the role and interactions of catalytic residues with ligand were also described. The substrate binding pocket of βManAo was found to be highly dynamic and showed large, concerted movements. The outcomes of the present study can be exploited in further understanding the structural properties and functional dynamics of βManAo.

Does supplementing β-mannanase modulate the feed-induced immune response and gastrointestinal ecology in poultry and pigs? An appraisal

The provision of adequate and balanced nutrients is critical for efficient and profitable animal protein production. However, non-nutritive components in feedstuffs can elicit responses that can negatively impact nutrient utilization efficiency. For example, dietary β-mannans are recognizable by cell surface mannose receptors are pivotal for diverse cellular functions. This review will evaluate the physiological implications of dietary native β-mannans, the utility of supplemental feed β-mannanase in hydrolyzing β-mannans, and subsequent metabolic responses. Dietary native β-mannans have been implicated in inadvertent stimulation of immune response through a phenomenon called the feed-induced immune response (FIIR), that has been associated with intestinal inflammation and depression in animal performance. Supplemental β-mannanase blunted the FIIR by hydrolyzing native β-mannans to smaller fragments with a reduced ability to stimulate the innate immune system as indicated by the modulation of oxidative stress, mucosal permeability, and blood concentration of acute phase proteins and immunoglobulins in broilers and piglet models. Moreover, β-mannanase hydrolysis of native β-mannans to mannooligosaccharides (MOS) impacted gastrointestinal microbial ecology. Indeed, β-mannanase-derived MOS reduced the concentration of pathogenic bacteria such as Escherichia coli and Salmonella and increased the production of short-chain fatty acids in gastrointestinal tracts of various animal models. Consequently, by hydrolyzing native β-mannans, supplemental β-mannanase may have nutritional, metabolic, and microbial ecology benefits. In summary, integrating multi-functional feed additives such as β-mannanase into feeding programs for monogastric animals will be critical for efficient and sustainable animal protein production in the context of evolving challenges such as the mandated elimination of use of antibiotics for growth promotion.

Production and characterization of thermostable acidophilic β-mannanase from Aureobasidium pullulans NRRL 58524 and its potential in mannooligosaccharide production from spent coffee ground galactomannan

The maximum yield of the crude mannanase from Aureobasidium pullulans NRRL 58524 was 8.42 ± 0.18 U mL-1 when cultured for 72 h in the optimized medium containing 3% (w v-1) defatted spent coffee grounds (SCG) and 0.67% (w v-1) ammonium sulphate. Two forms of mannanase were observed in the crude enzyme and the principal mannanase was enriched to apparent homogeneity via sequential filtration and anion exchange chromatography. The molecular mass of the enzyme was approximately 63 kDa as determined by SDS-PAGE. The enriched mannanase was active at high temperatures (45-75 °C) and a pH range from 3 to 6 with the maximum activity at 55 °C and pH 4.0. The enzyme was relatively thermostable with more than 75% of its initial activity remained after a 12 h incubation at 55 °C. The half-lives of the enriched mannanase were over 8 and 6 h at 60 and 65 °C, respectively. The enzyme was not adversely affected by chelator and most ions tested. This enzyme could hydrolyze both glucomannan and galactomannan and exhibited limited catalytic activity on beta-glucan. When the crude mannanase was used to hydrolyze galactomannan extracted from SCG, the maximum yield of reducing sugars mainly comprising of mannobiose (16.27 ± 0.84 mg 100 mg-1), and mannotriose (2.85 ± 0.20 mg 100 mg-1) was obtained at 58.22 ± 2.04 mg 100 mg-1 dry weight, under optimized condition (84.87 U g-1 mannanase, 41 h 34 min incubation at 55 °C and pH 4.0). These results suggested the prospect of the enzyme in mannan hydrolysis and mannooligosaccharide production at a larger scale.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03301-4.

Stachybotrys chartarum-A Hidden Treasure: Secondary Metabolites, Bioactivities, and Biotechnological Relevance

Fungi are renowned as a fountainhead of bio-metabolites that could be employed for producing novel therapeutic agents, as well as enzymes with wide biotechnological and industrial applications. Stachybotrys chartarum (black mold) (Stachybotriaceae) is a toxigenic fungus that is commonly found in damp environments. This fungus has the capacity to produce various classes of bio-metabolites with unrivaled structural features, including cyclosporins, cochlioquinones, atranones, trichothecenes, dolabellanes, phenylspirodrimanes, xanthones, and isoindoline and chromene derivatives. Moreover, it is a source of various enzymes that could have variable biotechnological and industrial relevance. The current review highlights the formerly published data on S. chartarum, including its metabolites and their bioactivities, as well as industrial and biotechnological relevance dated from 1973 to the beginning of 2022. In this work, 215 metabolites have been listed and 138 references have been cited.

Short-chain β-manno-oligosaccharides from copra meal: structural characterization, prebiotic potential and anti-glycation activity

Size-exclusion chromatography, HR-ESI-MS and FT-IR of copra meal hydrolyzed by ManB-1601 showed the presence of oligosaccharides (CM-β-MOS) having a degree of polymerisation (DP) between 2 and 4. Thermal decomposition studies of the purified CM-β-MOS (DP 2, 3 and 4) showed mass loss at high temperatures (135.8 °C to 600 °C). DP2, DP3 and DP4 CM-β-MOS were adjudged as un-substituted Manβ-4Man, Manβ-4Manβ-4Man and Manβ-4Manβ-4Manβ-4Man, respectively, using NMR (¹H and ¹³C) studies. During fermentation, purified CM-β-MOS supported the growth of Lactobacillus sp. and inhibited enteropathogens (Escherichia coli, Listeria monocytogenes and Salmonella typhi). Acetate was the predominant short-chain fatty acid produced by Lactobacillus sp. RT-PCR studies of L. plantarum WCFS1 fed with CM-β-MOS showed up-regulation (up to 6.7-fold) of the cellobiose utilization operon (pts23C and pbg6) and oligo-sucrose utilization loci (pts1BCA and agl2). Biochemical (free amino groups, carbonyl and fructosamine content), fluorescence (AGEs-specific and intrinsic) and molecular docking studies suggested the anti-glycation potential of CM-β-MOS.

Antioxidant activity of yeast mannans and their growth-promoting effect on Lactobacillus strains

Yeast mannans from Saccharomyces cerevisiae (123.2 kDa, 40.5 kDa and 21.3 kDa) were prepared. The scavenging abilities of Fe²⁺, OH˙, and O₂˙^- and protective capacities against lipid peroxidation and oxidative DNA damage increased with the reduction of the molecular weights of yeast mannans. The highest scavenging abilities of Fe²⁺, OH˙ and O₂˙^- (25.32%, 70.8%, and 61.5%) were observed with YM-90, and it showed an anti-lipid peroxidation capacity of 65.82%, which was much stronger than that of vitamin C (VC), with a thiobarbituric acid-reactive substance (TBARS) inhibition rate of 80.41%. However, the highest DPPH scavenging rate (88.7%) was exhibited by YM-30. In addition, the growth-promoting effect of yeast mannans on Lactobacillus strains was further confirmed, and a 54.2% increment of Lactobacillus plantarum ZWR5 cell viability was achieved by YM-90. The results indicated the potential industrial applications of this yeast mannan technology in therapeutic and nutraceutical production.

Production and in vitro evaluation of prebiotic manno-oligosaccharides prepared with a recombinant Aspergillus niger endo-mannanase, Man26A

In this study, a GH26 endo-mannanase (Man26A) from an Aspergillus niger ATCC 10864 strain, with a molecular mass of 47.8 kDa, was cloned in a yBBH1 vector and expressed in Saccharomyces cerevisiae Y294 strain cells. Upon fractionation by ultra-filtration, the substrate specificity and substrate degradation pattern of the endo-mannanase (Man26A) were investigated using ivory nut linear mannan and two galactomannan substrates with varying amounts of galactosyl substitutions, guar gum and locust bean gum. Man26A exhibited substrate specificity in the order: locust bean gum ≥ ivory nut mannan > guar gum; however, the enzyme generated more manno-oligosaccharides (MOS) from the galactomannans than from linear mannan during extended periods of mannan hydrolysis. MOS with a DP of 2-4 were the major products from mannan substrate hydrolysis, while guar gum also generated higher DP length MOS. All the Man26A generated MOS significantly improved the growth (approximately 3-fold) of the probiotic bacterial strains Streptococcus thermophilus and Bacillus subtilis in M9 minimal medium. Ivory nut mannan and locust bean gum derived MOS did not influence the auto-aggregation ability of the bacteria, while the guar gum derived MOS led to a 50 % reduction in bacterial auto-aggregation. On the other hand, all the MOS significantly improved bacterial biofilm formation (approximately 3-fold). This study suggests that the prebiotic characteristics exhibited by MOS may be dependent on their primary structure, i.e. galactose substitution and DP. Furthermore, the data suggests that the enzyme-generated MOS may be useful as potent additives to dietary foods.

Enzymatic Conversion of Mannan-Rich Plant Waste Biomass into Prebiotic Mannooligosaccharides

A growing demand in novel food products for well-being and preventative medicine has attracted global attention on nutraceutical prebiotics. Various plant agro-processes produce large amounts of residual biomass considered "wastes", which can potentially be used to produce nutraceutical prebiotics, such as manno-oligosaccharides (MOS). MOS can be produced from the degradation of mannan. Mannan has a main backbone consisting of β-1,4-linked mannose residues (which may be interspersed by glucose residues) with galactose substituents. Endo-β-1,4-mannanases cleave the mannan backbone at cleavage sites determined by the substitution pattern and thus give rise to different MOS products. These MOS products serve as prebiotics to stimulate various types of intestinal bacteria and cause them to produce fermentation products in different parts of the gastrointestinal tract which benefit the host. This article reviews recent advances in understanding the exploitation of plant residual biomass via the enzymatic production and characterization of MOS, and the influence of MOS on beneficial gut microbiota and their biological effects (i.e., immune modulation and lipidemic effects) as observed on human and animal health.

BdPUL12 depolymerizes β-mannan-like glycans into mannooligosaccharides and mannose, which serve as carbon sources for Bacteroides dorei and gut probiotics

Symbiotic bacteria, including members of the Bacteroides genus, are known to digest dietary fibers in the gastrointestinal tract. The metabolism of complex carbohydrates is restricted to a specified subset of species and is likely orchestrated by polysaccharide utilization loci (PULs) in these microorganisms. β-Mannans are plant cell wall polysaccharides that are commonly found in human nutrients. Here, we report the structural basis of a PUL cluster, BdPUL12, which controls β-mannan-like glycan catabolism in Bacteroides dorei. Detailed biochemical characterization and targeted gene disruption studies demonstrated that a key glycoside hydrolase, BdP12GH26, performs the initial attack on galactomannan or glucomannan likely via an endo-acting mode, generating mannooligosaccharides and mannose. Importantly, coculture assays showed that the B. dorei promoted the proliferation of Lactobacillus helveticus and Bifidobacterium adolescentis, likely by sharing mannooligosaccharides and mannose with these gut probiotics. Our findings provide new insights into carbohydrate metabolism in gut-inhabiting bacteria and lay a foundation for novel probiotic development.

Hemicellulose-Derived Oligosaccharides: Emerging Prebiotics in Disease Alleviation

The gut microbiota in the human body is an important component that plays a pivotal role in the ability of the host to prevent diseases and recover from these diseases. If the human microbiome changes for any reason, it affects the overall functioning of the host. Healthy and vigorous gut microbiota require dietary fiber supplementation. Recently, oligosaccharides have been found to play a significant role in the modulation of microbiota. Several such oligosaccharides, i.e., xylooligosaccharides (XOS), mannooligosaccharides (MOS), and arabino-xylooligosaccharides (AXOS), are derived from hemicellulosic macromolecules such as xylan, mannan, and arabino-xylan, respectively. These oligosaccharides serve as substrates for the probiotic production of health-promoting substances (short-chain fatty acids, branched chain amino acids etc.), which confer a variety of health benefits, including the prevention of some dreaded diseases. Among hemicellulose-derived oligosaccharides (HDOs), XOS have been largely explored, whereas, studies on MOS and AXOS are currently underway. HDOs, upon ingestion, help reduce morbidities by lowering populations of harmful or pathogenic bacteria. The ATP-binding cassette (ABC) transporters are mainly utilized for the uptake of oligosaccharides in probiotics. Butyrate generated by the selective fermentation of oligosaccharides, along with other short-chain fatty acids, reduces gut inflammation. Overall, oligosaccharides derived from hemicelluloses show a similar potential as conventional prebiotics and can be supplemented as functional foods. This review summarizes the role of HDOs in the alleviation of autoimmune diseases (inflammatory bowel disease, Crohn's disease), diabetes, urinary tract infection, cardiovascular diseases, and antimicrobial resistance (AMR) through the modulation of the gut microbiota. The mechanism of oligosaccharide utilization and disease mitigation is also explained.

Functional and structural investigation of a novel β-mannanase BaMan113A from Bacillus sp. N16-5

Mannan is an important renewable resource whose backbone can be hydrolyzed by β-mannanases to generate manno-oligosaccharides of various sizes. Only a few glycoside hydrolase (GH) 113 family β-mannanases have been functionally and structurally characterize. Here, we report the function and structure of a novel GH113 β-mannanase from Bacillus sp. N16-5 (BaMan113A). BaMan113A exhibits a substrate preference toward manno-oligosaccharides and releases mannose and mannobiose as main hydrolytic products. The crystal structure of BaMan113A suggest that the enzyme shows a semi-enclosed substrate-binding cleft and the amino acids surrounding the +2 subsite form a steric barrier to terminate the substrate-binding tunnel. Based on these structural features, we conducted mutagenesis to engineer BaMan113A to remove the steric hindrance of the substrate-binding tunnel. We found that F101E and N236Y variants exhibit increased specific activity toward mannans comparing to the wild-type enzyme. Meanwhile, the product profiles of these two variants toward polysaccharides changed from mannose to a series of manno-oligosaccharides. The crystal structure of variant N236Y was also determined to illustrate the molecular basis underlying the mutation. In conclusion, we report the functional and structural features of a novel GH113 β-mannanase, and successfully improved its endo-acting activity by using structure-based engineering.