Applications of Microbial β-Mannanases

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.

Carbohydrate polymer degradation derivatives as possible natural mannanase inhibitors

The role of mannanases is diverse and they are used in many industrial applications, in animal feed, in the food industry and in healthcare. They are also applied in biomass processing, because they play an important role in the breakdown of hemicellulose. Among the mannanase inhibitors, heavy metal ions and general enzyme inhibitors are mainly mentioned. Unfortunately, almost no data are available on carbohydrate-based natural inhibitors of mannanases. According to the literature, carbohydrates do not play an important role in the inhibition of mannanases, so neither do oligosaccharides. This is in contrast to the action and inhibition of other O-glycosyl hydrolases. My hypothesis is that mannanases, like other polysaccharide-degrading enzymes, work in the same way and can be inhibited by oligosaccharides. Evidence from docking and modeling results supports and makes probable the hypothesis that oligosaccharides can inhibit the activity of mannanases, similar to the inhibition of other O-glycosyl hydrolases. Among natural carbohydrate oligomers, several potential mannanase inhibitors have been identified and characterized. In addition to expensive research, it is very important to use research based on cheaper modeling to explore the processes. The results obtained are novel and forward-looking, enabling in-depth and targeted research to be carried out.

Research and application progress of microbial β-mannanases: a mini-review

Mannan is a predominant constituent of cork hemicellulose and is widely distributed in various plant tissues. β-Mannanase is the principal mannan-degrading enzyme, which breaks down the β-1,4-linked mannosidic bonds in mannans in an endo-acting manner. Microorganisms are a valuable source of β-mannanase, which exhibits catalytic activity in a wide range of pH and temperature, making it highly versatile and applicable in pharmaceuticals, feed, paper pulping, biorefinery, and other industries. Here, the origin, classification, enzymatic properties, molecular modification, immobilization, and practical applications of microbial β-mannanases are reviewed, the future research directions for microbial β-mannanases are also outlined.

Trends in the development and current perspective of thermostable bacterial hemicellulases with their industrial endeavors: A review

Hemicellulases are enzymes that hydrolyze hemicelluloses, common polysaccharides in nature. Thermophilic hemicellulases, derived from microbial strains, are extensively studied as natural biofuel sources due to the complex structure of hemicelluloses. Recent research aims to elucidate the catalytic principles, mechanisms and specificity of hemicellulases through investigations into their high-temperature stability and structural features, which have applications in biotechnology and industry. This review article targets to serve as a comprehensive resource, highlighting the significant progress in the field and emphasizing the vital role of thermophilic hemicellulases in eco-friendly catalysis. The primary goal is to improve the reliability of hemicellulase enzymes obtained from thermophilic bacterial strains. Additionally, with their ability to break down lignocellulosic materials, hemicellulases hold immense potential for biofuel production. Despite their potential, the commercial viability is hindered by their high enzyme costs, necessitating the development of efficient bioprocesses involving waste pretreatment with microbial consortia to overcome this challenge.

Thermophilic β-mannanases from bacteria: production, resources, structural features and bioengineering strategies

β-mannanases are pivotal enzymes that cleave the mannan backbone to release short chain mannooligosaccharides, which have tremendous biotechnological applications including food/feed, prebiotics and biofuel production. Due to the high temperature conditions in many industrial applications, thermophilic mannanases seem to have great potential to overcome the thermal impediments. Thus, structural analysis of thermostable β-mannanases is extremely important, as it could open up new avenues for genetic engineering, and protein engineering of these enzymes with enhanced properties and catalytic efficiencies. Under this scope, the present review provides a state-of-the-art discussion on the thermophilic β-mannanases from bacterial origin, their production, engineering and structural characterization. It covers broad insights into various molecular biology techniques such as gene mutagenesis, heterologous gene expression, and protein engineering, that are employed to improve the catalytic efficiency and thermostability of bacterial mannanases for potential industrial applications. Further, the bottlenecks associated with mannanase production and process optimization are also discussed. Finally, future research related to bioengineering of mannanases with novel protein expression systems for commercial applications are also elaborated.

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.

Mannanase improves the growth performance of broilers by alleviating inflammation of the intestinal epithelium and improving intestinal microbiota

This experiment aimed to discuss and reveal the effect and mechanism of mannanase on intestinal inflammation in broilers triggered by a soybean meal diet. In this experiment, 384 Arbor Acres broilers at 1 d old were randomly divided into 3 treatment groups. The broilers were fed a corn-soybean meal basal diet, a low-energy diet (metabolizable energy reduced by 50 kcal/kg), and a low-energy diet supplemented with 100 mg/kg mannanase for 42 d. The low-energy diet increased feed conversion ratio from 0 to 42 d, reduced ileal villus height and villus height-to-crypt depth ratio and upregulated the expression of nuclear factor kappa B (NF-κB) in the ileum (P < 0.05). It also reduced cecal short-chain fatty acids (SCFA), such as acetic acid (P < 0.05). Compared with low-energy diets, the addition of mannanase increased body weight at 42 d, promoted the digestibility of nutrients, and maintained the morphology and integrity of the intestinal epithelium of broilers (P < 0.05). In addition, mannanase upregulated the expression of claudin-1 (CLDN1) and zonula occludens-1 (ZO-1) in the jejunum at 21 d, downregulated the expression of ileal NF-κB, and increased the content of isobutyric acid in the cecum of broilers (P < 0.05). The results for the ileal microbiota showed that a low-energy diet led to a decrease in the relative abundance of Lactobacillus reuteri in the ileum of broilers. The addition of mannanase increased the relative abundance of Lactobacillus-KC45b and Lactobacillus johnsonii in broilers. Furthermore, a low-energy diet reduced the relative abundance of Butyricicoccus in the intestine of broilers and inhibited oxidative phosphorylation and phosphoinositol metabolism. Mannanase increased the relative abundance of Odoribacter, promoted energy metabolism and N-glycan biosynthesis, and increased the activities of GH3 and GH18. It is concluded that mannanase could improve the growth performance of broilers by reducing the expression of NF-κB in the ileum, increasing the production of SCFA in the cecum, suppressing intestinal inflammation, balancing the intestinal microbiota, reducing damage to the intestinal barrier, and improving the efficiency of nutrient utilization to alleviate the adverse effects caused by the decrease in dietary energy level.

The genus Acrophialophora: History, phylogeny, morphology, beneficial effects and pathogenicity

The genus Acrophialophora is a thermotolerant fungus, which is widely distributed in temperate and tropical zones. This fungus is classified in Ascomycota and belongs to the Chaetomiaceae family and the genera of Parathielavia, Pseudothielavia and Hyalosphaerella are closely related to Acrophialophora. For this genus have been reported 28 species so far, which two species of Acrophialophora jodhpurensis and Acrophialophora teleoafricana produce only sexual phase and other species produce asexual form. Therefore, producing both sexual and asexual forms were not reported by any species. Many applications were reported by some species in agriculture, pharmacy and industry. Production of enzymes, antimicrobial metabolites and plant growth-promoting factors were reported by some species. The species of A. nainiana is used in the industries of textile, fruit juice, pulp and paper due to extracellular enzyme production. Also, other species produce extracellular enzymes that can be used in various industries. The species Acrophialophora are used in the composting industry due to the production of various enzymes and to be thermotolerant. In addition, some species were isolated from hostile environmental conditions. Therefore has been suggested that it can be used for mycoremediation. Also, antimicrobial metabolites of Acrophialophora have been reported to be effective against human and plant pathogens. In contrast to the beneficial effects described, the Acrophialophora pathogenicity has been rarely reported. Two species A. fusispora and A. levis are opportunistic fungi and have been reported as pathogens in humans, animals and plants. Currently, the development and applications of Acrophialophora species have increased more than past. To our knowledge, there is no report with comprehensive information on the species of Acrophialophora, which include their disadvantage and beneficial effects, particularly in agriculture. Therefore, it seems necessary to pay more in-depth attention to the application of this genus as a beneficial fungus in agriculture, pharmaceutical and industry. This review is focused on the history, phylogeny, morphology, valuable roles of Acrophialophora and pathogenicity.

Production of β-mannanase, inulinase, and oligosaccharides from coffee wastes and extracts

This study aimed to produce enzymes (beta (β)-mannanase using a recombinant Aspergillus sojae AsT3 and inulinase using Aspergillus niger A42) and oligosaccharides (mannooligosaccharides (MOS), fructooligosaccharides (FOS)) using coffee waste, ground coffee, and coffee extract by solid-state fermentation (SSF). Plackett-Burman Design (PBD) was used to create a design for enzyme production with four different parameters (temperature, pH, solid-to-liquid ratio (SLR), and mix with coffee wastes and ground coffee). The highest β-mannanase and inulinase activities were 71.17 and 564.07 U/mg of protein respectively. Statistical analysis showed that the temperature was statistically significant for the production of both enzymes (P < 0.05). The produced enzymes were utilized in French Pressed coffee extracts to produce oligosaccharides. As a result of the enzymatic hydrolyzation, the highest mannobiose, mannotriose, mannotetraose, and total MOS levels were 109.66, 101.11, 391.02, and 600.64 ppm, respectively. For the FOS production, the maximal 1,1,1-kestopentaose was 38.34 ppm. Consequently, this study demonstrates that a recombinant Aspergillus sojae AsT3 β-mannanase and Aspergillus niger A42 inulinase produced from coffee wastes and ground coffee can be used in coffee extracts to increase the amount of oligosaccharides in coffee extracts.

Komagataella phaffii as a Platform for Heterologous Expression of Enzymes Used for Industry

In the 1980s, Escherichia coli was the preferred host for heterologous protein expression owing to its capacity for rapid growth in complex media; well-studied genetics; rapid and direct transformation with foreign DNA; and easily scalable fermentation. Despite the relative ease of use of E. coli for achieving the high expression of many recombinant proteins, for some proteins, e.g., membrane proteins or proteins of eukaryotic origin, this approach can be rather ineffective. Another microorganism long-used and popular as an expression system is baker's yeast, Saccharomyces cerevisiae. In spite of a number of obvious advantages of these yeasts as host cells, there are some limitations on their use as expression systems, for example, inefficient secretion, misfolding, hyperglycosylation, and aberrant proteolytic processing of proteins. Over the past decade, nontraditional yeast species have been adapted to the role of alternative hosts for the production of recombinant proteins, e.g., Komagataella phaffii, Yarrowia lipolytica, and Schizosaccharomyces pombe. These yeast species' several physiological characteristics (that are different from those of S. cerevisiae), such as faster growth on cheap carbon sources and higher secretion capacity, make them practical alternative hosts for biotechnological purposes. Currently, the K. phaffii-based expression system is one of the most popular for the production of heterologous proteins. Along with the low secretion of endogenous proteins, K. phaffii efficiently produces and secretes heterologous proteins in high yields, thereby reducing the cost of purifying the latter. This review will discuss practical approaches and technological solutions for the efficient expression of recombinant proteins in K. phaffii, mainly based on the example of enzymes used for the feed industry.

A review of the principles and biotechnological applications of glycoside hydrolases from extreme environments

It is apparent that Biocatalysts are shaping the future by providing a more sustainable approach to established chemical processes. Industrial processes rely heavily on the use of toxic compounds and high energy or pH reactions, factors that both contributes to the worsening climate crisis. Enzymes found in bacterial systems and other microorganisms, from the glaciers of the Arctic to the sandy deserts of Abu Dhabi, provide key tools and understanding as to how we can progress in the biotechnology sector. These extremophilic bacteria harness the adaptive enzymes capable of withstanding harsh reaction conditions in terms of stability and reactivity. Carbohydrate-active enzymes, including glycoside hydrolases or carbohydrate esterases, are extremely beneficial for the presence and future of biocatalysis. Their involvement in the industry spans from laundry detergents to paper and pulp treatment by degrading oligo/polysaccharides into their monomeric products in almost all detrimental environments. This includes exceedingly high temperatures, pHs or even in the absence of water. In this review, we discuss the structure and function of different glycoside hydrolases from extremophiles, and how they can be applied to industrial-scale reactions to replace the use of harsh chemicals, reduce waste, or decrease energy consumption.

Identification and Characterization of a Novel Mannanase from Klebsiella grimontii

Konjac glucomannan (KGM) is a natural polysaccharide derived from konjac, which has been widely used in various fields due to its numerous beneficial properties. However, the high viscosity and water absorption of KGM limit its application. Compared with KGM, Konjac glucomannan oligosaccharides (KGMOS) have higher water solubility and stronger application value. In this paper, a novel mannanase KgManA was cloned from Klebsiella grimontii to develop a new KGMOS-producing enzyme. Bioinformatic analysis shows that the structural similarity between KgManA and other enzymes was less than 18.33%. Phylogenetic analysis shows that KgManA shares different branches with the traditional mannanases containing the CMB35 domain, indicating that it is a novel mannanase. Then, the enzymatic properties were determined and substrate specificity was characterized. Surprisingly, KgManA is stable in a very wide pH range of 3.0 to 10.0; it has a special substrate specificity and seems to be active only for mannans without galactose in the side chain. Additionally, the three-dimensional structure of the enzyme was simulated and molecular docking of the mannotetraose substrate was performed. As far as we know, this is the first report to characterize the enzymatic properties and to simulate the structure of mannanase from K. grimontii. This work will contribute to the development and characterization of novel K. grimontii-derived mannanases. The above results indicate that KgManA is a promising tool for the production of KGMOS.

Engineered Alcaligenes sp. by chemical mutagen produces thermostable and acido-alkalophilic endo-1,4-β-mannanases for improved industrial biocatalyst

This study reported physicochemical properties of purified endo-1,4-β-mannanase from the wild type, Alcaligenes sp. and its most promising chemical mutant. The crude enzymes from fermentation of wild and mutant bacteria were purified by ammonium sulfate precipitation, ion exchange and gel-filtration chromatography followed by an investigation of the physicochemical properties of purified wild and mutant enzymes. β-mannanase from wild and mutant Alcaligenes sp. exhibited 1.75 and 1.6 purification-folds with percentage recoveries of 2.6 and 2.5% and molecular weights of 61.6 and 80 kDa respectively. The wild and mutant β-mannanase were most active at 40 and 50 °C with optimum pH 6.0 for both and were thermostable with very high percentage activity but the wild-type β-mannanase showed better stability over a broad pH activity. The β-mannanase activity from the parent strain was stimulated in the presence of Mn2+, Co2+, Zn2+, Mg2+ and Na+. Vmax and Km for the wild type and its mutant were found to be 0.747 U//mL/min and 5.2 × 10-4 mg/mL, and 0.247 U/mL/min and 2.47 × 10-4 mg/mL, respectively. Changes that occurred in the nucleotide sequences of the most improved mutant may be attributed to its thermo-stability, thermo-tolerant and high substrate affinity- desired properties for improved bioprocesses.

High NaCl concentrations induce the resistance to thermal denaturation of an extremely halotolerant (salt-activated) β-mannanase from Bacillus velezensis H1

β-mannanase catalyzes the hydrolysis of mannans β-1,4-mannosidic linkages to produce industrially relevant oligosaccharides. These enzymes have numerous important applications in the detergent, food, and feed industries, particularly those that are resistant to harsh environmental conditions such as salts and heat. While, moderately salt-tolerant β-mannanases are already reported, existence of a high halotolerant β-mannanase is still elusive. This study aims to report the first purification and characterization of ManH1, an extremely halotolerant β-mannanase from the halotolerant B. velezensis strain H1. Electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) analysis revealed a single major peak with a molecular mass of 37.8 kDa demonstrating its purity. The purified enzyme showed a good thermostability as no activity was lost after a 48 h incubation under optimal conditions of 50 °C and pH 5.5. The enzyme's salt activation nature was revealed when its maximum activity was obtained in the presence of 4 M NaCl, it doubled compared to the no-salt condition. Moreover, NaCl strengthens its resistance to thermal denaturation, as its melting temperature (Tm) increased steadily with increasing NaCl concentrations reaching 75.5 °C in the presence of 2.5 M NaCl. The Km and Vmax values were 5.63 mg/mL and 333.33 µmol/min/mL, respectively, using carob galactomannan (CG) as a substrate. The enzyme showed a significant ability to produce manno-oligosaccharides (MOS) from lignocellulosic biomass releasing 13 mg/mL of reducing sugars from olive mill wastes (OMW) after 24 h incubation. The results revealed that this enzyme may have significant commercial values for agro-waste treatment, and other potential applications.

In vitro assessment of the immobilized mannanase enzyme against infection-causing Candida

Background: Developing an effective treatment for fungal infections is among contemporary medicine's challenges. In this study we aimed to eradicate mannan in pathogenic Candidae's cell walls using a nontoxic method, mannanase. Materials & Methods: We investigated the in vitro antifungal activities of mannanase immobilized on zinc oxide nanoparticles (ZnONps) and reduced graphene oxide nanoparticles (RGONps), as well as therapeutics against Candidae. Mannanase was purified from Bacillus invictae (activity: 5.15 EU/ml; range: 60-80%) and then immobilized it to ZnO and RGO to enhance its effectiveness. Results: Mannanase immobilized on ZnONps had the highest activity, with a value of 4.97 EU/ml, more effective than amphotericin-B. However, it could not reach the inhibition rates of other antifungals. Conclusion: Mannanase immobilized on ZnONps could be an effective fungicide for Candida biocontrol.

Glycoside hydrolases from (hyper)thermophilic archaea: structure, function, and applications

(Hyper)thermophilic archaeal glycosidases are enzymes that catalyze the hydrolysis of glycosidic bonds to break down complex sugars and polysaccharides at high temperatures. These enzymes have an unique structure that allows them to remain stable and functional in extreme environments such as hot springs and hydrothermal vents. This review provides an overview of the current knowledge and milestones on the structures and functions of (hyper)thermophilic archaeal glycosidases and their potential applications in various fields. In particular, this review focuses on the structural characteristics of these enzymes and how these features relate to their catalytic activity by discussing different types of (hyper)thermophilic archaeal glycosidases, including β-glucosidases, chitinase, cellulases and α-amylases, describing their molecular structures, active sites, and mechanisms of action, including their role in the hydrolysis of carbohydrates. By providing a comprehensive overview of (hyper)thermophilic archaeal glycosidases, this review aims to stimulate further research into these fascinating enzymes.

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.

An integrated approach for pulp biobleaching: application of cocktail of enzymes

One of the paper industry's major focuses is shifting toward eco-friendly paper production. Chemical-based bleaching of pulp, which is widely used in the paper industry, is a highly polluting step. Replacing it with enzymatic biobleaching is the most viable alternative to make the process of papermaking greener. Enzymes such as xylanase, mannanase, and laccase are suitable for the biobleaching of pulp, which involves the removal of hemicelluloses, lignins, and other undesirable components. However, as no single enzyme can achieve this, their application in industry is limited. To overcome these limitations, a cocktail of enzymes is required. A number of strategies have been explored for the production and application of a cocktail of enzymes for pulp biobleaching, but no comprehensive information is available in the literature. The present short communication has summarized, compared, and discussed the various studies in this regard, which will be highly useful to pursue further research in this regard and make the process of papermaking greener.

Characterization of a novel GH26 β-mannanase from Paenibacillus polymyxa and its application in the production of mannooligosaccharides

A novel glycoside hydrolase family 26 β-mannanase gene ppman26a was cloned from Paenibacillus polymyxa KF-1. The full-length enzyme PpMan26A and its truncated products CBM35pp (aa 35-328) and PpMan26A-Δ205 (aa 206-656) were overexpressed in Escherichia coli. PpMan26A hydrolyzed locust bean gum, guar gum, konjac gum and ivory nut mannan, with the highest specific activity toward konjac gum. The K_m and k_cat values for konjac gum were 2.13 mg/mL and 416.66 s^-1, respectively. The oligosaccharides fraction obtained from the hydrolysis of konjac gum by PpMan26A was analyzed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometer (MALDI-TOF-MS). The degradation products were mainly mannooligosaccharides with a degree of polymerization of 3-8. CBM35pp exerted strong binding activity toward mannans but without β-mannanase activity. PpMan26A-Δ205, with the deletion of the N-terminal CBM domain, showed lower substrate binding capacity, resulting in reduced enzymatic activity and thermostability. This study complements our understanding of GH26 β-mannanases and expands the potential industrial application of PpMan26A.

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.

Trait biases in microbial reference genomes

Common culturing techniques and priorities bias our discovery towards specific traits that may not be representative of microbial diversity in nature. So far, these biases have not been systematically examined. To address this gap, here we use 116,884 publicly available metagenome-assembled genomes (MAGs, completeness ≥80%) from 203 surveys worldwide as a culture-independent sample of bacterial and archaeal diversity, and compare these MAGs to the popular RefSeq genome database, which heavily relies on cultures. We compare the distribution of 12,454 KEGG gene orthologs (used as trait proxies) in the MAGs and RefSeq genomes, while controlling for environment type (ocean, soil, lake, bioreactor, human, and other animals). Using statistical modeling, we then determine the conditional probabilities that a species is represented in RefSeq depending on its genetic repertoire. We find that the majority of examined genes are significantly biased for or against in RefSeq. Our systematic estimates of gene prevalences across bacteria and archaea in nature and gene-specific biases in reference genomes constitutes a resource for addressing these issues in the future.

Advances in extraction, purification, structural characteristics and biological activities of hemicelluloses: A review

Hemicelluloses, a major component of plant cell walls, are a non-cellulosic heteropolysaccharide composed of several distinct sugars that is second in abundance to cellulose, which are one of the most abundant and cheapest renewable resources on earth. Hemicelluloses structure is complex and its chemical structure varies greatly among the different plant species. In addition to its wide use in production of feed and other chemical materials, hemicelluloses are known for its remarkable biological activities that remain largely underutilised to date. Therefore, comprehensive investigations of hemicelluloses structural and biological properties would be helpful for achieving rational utilisation and high-value conversion of this underutilised substance into agents with enhanced health benefits for incorporation in drugs and health foods. In this review, details of diverse research initiatives that have enhanced our understanding of hemicelluloses properties are summarised, including hemicelluloses sources, extraction and purification methods, structural characteristics and biological activities. Furthermore, hemicelluloses structure-activity relationships and new directions for future hemicelluloses research studies are discussed.

Isolation and Characterization of Mannanase-Producing Bacteria for Potential Synbiotic Application in Shrimp Farming

Prebiotics such as mannan-oligosaccharides (MOS) are a promising approach to improve performance and disease resistance in shrimp. To improve prebiotic utilization, we investigated the potential probiotics and their feasibility of synbiotic use in vitro. Two bacterial isolates, Man26 and Man122, were isolated from shrimp intestines and screened for mannanase, the enzyme for mannan digestion. The crude mannanase from both isolates showed optimal activities at pH 8 with optimum temperatures at 60 °C and 50 °C, respectively. The enzymes remained stable at pH 8−10 for 3 h (>70% relative activity). The thermostability range of Man26 was 20−40 °C for 20 min (>50%), while that of Man122 was 20−60 °C for 30 min (>50%). The Vmax of Man122 against locust bean gum substrate was 41.15 ± 12.33 U·mg−1, six times higher than that of Man26. The Km of Man26 and Man122 were 18.92 ± 4.36 mg·mL−1 and 34.53 ± 14.46 mg·mL−1, respectively. With the addition of crude enzymes, reducing sugars of copra meal, palm kernel cake, and soybean meal were significantly increased (p < 0.05), as well as protein release. The results suggest that Man26 and Man122 could potentially be used in animal feeds and synbiotically with copra meal to improve absorption and utilization of feedstuffs.

Effect of dietary β-mannanase supplementation on growth performance, digestibility, and gene expression levels of Cyprinus carpio (Linnaeus) fingerlings fed a plant protein-rich diet

The aim of this study was to assess possible beneficial effects of dietary β-mannanase supplementation on the nutrient digestibility, growth performance, digestive and metabolic enzyme activity, and immune response of common carp (Cyprinus carpio) fed plant protein-rich diets. An experiment was conducted in triplicate, and a total of 225 fingerlings of common carp with an average body weight of 13.17 ± 0.12 g were stocked in 15 fiberglass tanks (15 fish/tank). Five dietary treatments (control 35% crude protein, plant-rich basal diet without supplement and four diets supplemented with β-mannanase from two sources (commercially available and locally isolated), each at two dosage levels (500 and 1,000 U/kg diet) were prepared and fed to respective groups of fish, twice a day (8:00 AM and 4:00 PM) at 4 % body weight. During the trial, changes in the level of DO and temperature ranged from 5.5 to 6.1 mg L-1 and 21.5 to 23.5°C, respectively. At the end of the feeding experiment, all fish in each tank were weighed and counted to determine growth parameters, while for the study of other indices, nine samples/treatment group were selected. The results of the study indicated a positive effect of both sources and dosage levels of β-mannanase supplementation on all studied indices, that is, significantly improved (P < 0.05), growth performance (%weight gain, specific growth rate), survival %, hematological indices (RBC, Hb, HCT, and MCHC), immunological indices (lysozyme activity, WBC, respiratory burst activity, and phagocytic activity), improved apparent digestibility of nutrients (crude protein, crude fat, and carbohydrates), and digestible energy. Furthermore, higher activity (P < 0.05) of the digestive enzymes (cellulase, lipase, and protease) and upregulation of MyoD gene in muscle and TNF-α gene in liver, intestine, and muscle were also observed, while the activity of serum AST (serum aspartate aminotransferase) and ALT (alanine transaminase) as compared to control group was significantly decreased (P < 0.05). Based on the results, β-mannanase supplementation (500 U/kg) could be recommended for obtaining better carp production when low-cost plant protein-rich diets are used.

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.

Selection of pretreatment method and mannanase enzyme to improve the functionality of palm kernel cake

Palm kernel cake (PKC) is a by-product of palm kernel oil extraction with moderate nutritional value, containing 30-35% β-mannan, which is indigestible, slows growth, and reduces feed efficiency. PKC can be improved by mannanase hydrolysis, but the effectiveness of mannanase is dependent on the microbial source. Thus, the effect of steam pretreatment and bacterial mannanases on PKC quality was investigated. PKC was pretreated by steaming and hydrolyzed in the small intestine by various mannanases. The contents of reducing sugar, total sugar, and protein release were measured. Steamed PKC had a significant increase in protein (16.95 ± 0.14 to 20.98 ± 0.13%) and a substantial decrease in hemicellulose (29.52 ± 0.44 to 3.46 ± 0.88%) and lignin (8.94 ± 0.28 to 1.40 ± 0.22%). Mannanases from Escherichia coli-KMAN-3 and E. coli-Man6.7 recorded the highest activities, followed by commercial mannanase, Bacillus circulans NT6.7 and B. amyloliquefaciens NT6.3 mannanases, orderly. B. circulans NT6.7 and B. amyloliquefaciens NT6.3 had multi-activities that include glucanase (3.10 ± 0.04% and 2.47 ± 0.02%) and amylase (1.74 ± 0.03% and 1.38 ± 0.04%), respectively. B. amyloliquefaciens NT6.3 mannanase hydrolyzed steamed PKC to release more reducing sugar, total sugar, and protein than hydrolyzed raw PKC. In raw and steamed PKC, B. amyloliquefaciens NT6.3 mannanase produced the highest reducing sugar release. As a result, steam pretreatment and mannanase hydrolysis, particularly from B. amyloliquefaciens, can be used to increase the functioning of PKC and develop new feed ingredients for monogastric animals at a reasonable cost.

Modifying Thermostability and Reusability of Hyperthermophilic Mannanase by Immobilization on Glutaraldehyde Cross-Linked Chitosan Beads

In the current study, the purified β-mannanase (Man/Cel5B) from Thermotoga maritima was immobilized on glutaraldehyde cross-linked chitosan beads. The immobilization of Man/Cel5B on chitosan beads was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. After immobilization, the protein loading efficiency and immobilization yield were found to be 73.3% and 71.8%, respectively. The optimum pH for both free and immobilized enzymes was found to be pH 5.5. However, the optimum temperature of immobilized Man/Cel5B increased by 10 °C, from 85 °C (free Man/Cel5B) to 95 °C (Immobilized). The half-life of free and immobilized enzymes was found to be 7 h and 9 h, respectively, at 85 °C owing to the higher thermostability of immobilized Man/Cel5B. The increase in thermostability was also demonstrated by an increase in the energy of deactivation (209 kJmol⁻¹) for immobilized enzyme compared to its native form (92 kJmol⁻¹), at 85 °C. Furthermore, the immobilized Man/Cel5B displayed good operational stability as it retained 54% of its original activity after 15 repeated catalytic reactions concerning its free form.

Co-production of schizophyllan and cellulolytic enzymes from bagasse by Schizophyllum commune

Schizophyllum commune is a mushroom-forming fungus well-known for its ability to degrade lignocellulosic materials and production of schizophyllan, a high added-value product for cosmeceutical, pharmaceutical and biomaterial industries. Conventionally, schizophyllan is produced by submerged fermentation using glucose as carbon source. In this work, we demonstrate that alkaline pretreated bagasse can be used by Schizophyllum commune as an alternative carbon source for the production of schizophyllan. The influence of different factors was investigated including cultivation time, biomass loading, and culturing media component and a co-product correlation model was proposed. In this lab-scale study, a yield of 4.4 g/L of schizophyllan containing 89% glucose was achieved. In addition to schizophyllan, the cellulolytic enzymes co-produced during this process were isolated and characterized and could find applications in a range of industrial processes. This demonstrates the potential of using agricultural waste as a cheaper alternative feedstock for this biorefinery process.

Genome sequencing of a novel Microbacterium camelliasinensis CIAB417 identified potential mannan hydrolysing enzymes

Here, whole genome sequencing of Microbacterium sp. CIAB417 was conducted to determine its novelty at species level and identification of genes encoding for enzymes for mannan degradation. The draft genome was predicted to have 6.53 mbp length represented by 41 contigs and 6078 genes. However, only 82.35% genes were allocated for their functions. The whole genome phylogeny, ANI score (78.84%), GGDC (genome to genome distance calculations) show probability (DDH ≥ 70%) equal to 0% and difference in advanced biochemical properties among closely predicted species. The Microbacterium sp. CIAB417 was stipulated to be novel at species level. Isolate was named as Microbacterium camelliasinensis CIAB417 (accession no JAHZUT000000000) based on its isolation from a tea garden soil. Genome was predicted for three novel mannanase coding genes man1 (MZ702740), man2 (MZ702741), and man3 (MZ702737) that belong to the GH5 and GH113 family. Besides that, mannan side chain hydrolysing enzymes alpha-galactosidase (gla1; MZ702739) and beta-glucosidase (glu1; MZ702738) were also predicted.

Fractionation of the water insoluble part of the heterotrophic mutant green microalga Parachlorella kessleri HY1 (Chlorellaceae) biomass: Identification and structure of polysaccharides

The water-insoluble part of Parachlorella kessleri HY1 biomass was subjected to the extraction of cell-wall polysaccharides using polar aprotic solvents (DMSO, LiCl/DMSO) and aqueous alkaline solutions (0.1, 1 and 4 mol·l^-1 of NaOH). Proteins predominated in all the crude extracts and in the insoluble residues were partially removed by treatment with proteolytic enzymes (pepsin and pronase), and in some cases with the HCl/H₂O₂ reagent, yielding purified polysaccharide-enriched fractions. These treatments led to the solubilisation of some products in water. The composition and structure of isolated polysaccharides were characterised based on monosaccharide composition, glycosidic linkage and spectroscopic analyses. The DMSO extract contained mainly proteins, and polysaccharides were not detected. The water-soluble parts isolated from the LiCl/DMSO extract contained α-l-rhamnan, α-d-glucan and β-d-glucogalactan; the water-insoluble part contained (1 → 4)-β-d-xylan, first isolated from the biomass of green microalgae. The alkali extracts contained polysaccharides of similar structure, and also water-insoluble (1 → 4)-β-d-mannan. The insoluble part after all extractions contained α-chitin as the main polysaccharide, which was confirmed by spectroscopic methods. All these polysaccharides can play a certain role in the cell wall structure of this microalga.

Impact of Modular Architecture on Activity of Glycoside Hydrolase Family 5 Subfamily 8 Mannanases

Glycoside hydrolase family 5 subfamily 8 (GH5_8) mannanases belong to Firmicutes, Actinomycetia, and Proteobacteria. The presence or absence of carbohydrate-binding modules (CBMs) present a striking difference. While various GH5_8 mannanases need a CBM for binding galactomannans, removal of the CBM did not affect activity of some, whereas it in other cases reduced the catalytic efficiency due to increased K_M. Here, monomodular GH5_8 mannanases from Eubacterium siraeum (EsGH5_8) and Xanthomonas citri pv. aurantifolii (XcGH5_8) were produced and characterized to clarify if GH5_8 mannanases from Firmicutes and Proteobacteria without CBM(s) possess distinct properties. EsGH5_8 showed a remarkably high temperature optimum of 55 °C, while XcGH5_8 had an optimum at 30 °C. Both enzymes were highly active on carob galactomannan and konjac glucomannan. Notably, EsGH5_8 was equally active on both substrates, whereas XcGH5_8 preferred galactomannan. The K_M values were comparable with those of catalytic domains of truncated GH5_8s, while the turn-over numbers (k_cat) were in the higher end. Notably, XcGH5_8 bound to but did not degrade insoluble ivory nut mannan. The findings support the hypothesis that GH5_8 mannanases with CBMs target insoluble mannans found in plant cell walls and seeds, while monomodular GH5_8 members have soluble mannans and mannooligosaccharides as primary substrates.

Delayed Breaker Systems To Remove Residual Polymer Damage in Hydraulically Fractured Reservoirs

Hydraulic fracturing is a widely used technology to enhance the productivity of low-permeability reservoirs. Fracturing fluids using guar as the rheology builder leaves aside residual polymer layers over the fractured surface, resulting in a restricted matrix to fracture flow, causing reduced well productivity and injectivity. This research developed a specialized enzyme breaker and evaluated its efficiency in breaking linear and cross-linked guar-polymer gel as a function of time, temperature, and breaker concentration targeting a high-temperature carbonate reservoir. The study began with developing a high-temperature stable galacto-mannanase enzyme using the "protein-engineering" approach, followed by the optimization of fracturing fluids and breaker concentrations measuring their rheological properties. The thermal stability of the enzyme breaker vis-à-vis viscosity reduction and the degradation pattern of the linear and cross-linked gel observed from the break tests showed that the enzyme is stable and active up to 120 °C and can reduce viscosity by more than 99%. Further studies conducted using a high-temperature high-pressure HT-HP filter press for the visual inspection of polymer cake quality, filtration loss rates, and cake dissolution efficiency showed that a 6 h enzyme treatment degrades the filter cake by 94-98% compared to 60-70% degradation in 72 h of the natural degradation process. Coreflooding studies, under simulated reservoir conditions, showed the severity of postfracture damage (up to 99%), which could be restored up to 95% on enzyme treatment depending on the treatment protocol and the type of fracturing gel used.

Value-Added Products from Ethanol Fermentation—A Review

Global demand for renewable and sustainable energy is increasing, and one of the most common biofuels is ethanol. Most ethanol is produced by Saccharomyces cerevisiae (yeast) fermentation of either crops rich in sucrose (e.g., sugar cane and sugar beet) or starch-rich crops (e.g., corn and starchy grains). Ethanol produced from these sources is termed a first-generation biofuel. Yeast fermentation can yield a range of additional valuable co-products that accumulate during primary fermentation (e.g., protein concentrates, water soluble metabolites, fusel alcohols, and industrial enzymes). Distillers’ solubles is a liquid co-product that can be used in animal feed or as a resource for recovery of valuable materials. In some processes it is preferred that this fraction is modified by a second fermentation with another fermentation organism (e.g., lactic acid bacteria). Such two stage fermentations can produce valuable compounds, such as 1,3-propanediol, organic acids, and bacteriocins. The use of lactic acid bacteria can also lead to the aggregation of stillage proteins and enable protein aggregation into concentrates. Once concentrated, the protein has utility as a high-protein feed ingredient. After separation of protein concentrates the remaining solution is a potential source of several known small molecules. The purpose of this review is to provide policy makers, bioethanol producers, and researchers insight into additional added-value products that can be recovered from ethanol beers. Novel products may be isolated during or after distillation. The ability to isolate and purify these compounds can provide substantial additional revenue for biofuel manufacturers through the development of marketable co-products.

Biotechnological potential of psychrophilic microorganisms as the source of cold-active enzymes in food processing applications

Microorganisms striving in extreme environments and exhibiting optimal growth and reproduction at low temperatures, otherwise known as psychrophilic microorganisms, are potential sources of cold-active enzymes. Owing to higher stability and cold activity, these enzymes are gaining enormous attention in numerous industrial bioprocesses. Applications of several cold-active enzymes have been established in the food industry, e.g., β-galactosidase, pectinase, proteases, amylases, xylanases, pullulanases, lipases, and β-mannanases. The enzyme engineering approaches and the accumulating knowledge of protein structure and function have made it possible to improve the catalytic properties of interest and express the candidate enzyme in a heterologous host for a higher level of enzyme production. This review compiles the relevant and recent information on the potential uses of different cold-active enzymes in the food industry.

Crystallization, structural characterization and kinetic analysis of a GH26 β-mannanase from Klebsiella oxytoca KUB-CW2-3

β-Mannanase (EC 3.2.1.78) is an enzyme that cleaves within the backbone of mannan-based polysaccharides at β-1,4-linked D-mannose residues, resulting in the formation of mannooligosaccharides (MOS), which are potential prebiotics. The GH26 β-mannanase KMAN from Klebsiella oxytoca KUB-CW2-3 shares 49-72% amino-acid sequence similarity with β-mannanases from other sources. The crystal structure of KMAN at a resolution of 2.57 Å revealed an open cleft-shaped active site. The enzyme structure is based on a (β/α)₈-barrel architecture, which is a typical characteristic of clan A glycoside hydrolase enzymes. The putative catalytic residues Glu183 and Glu282 are located on the loop connected to β-strand 4 and at the end of β-strand 7, respectively. KMAN digests linear MOS with a degree of polymerization (DP) of between 4 and 6, with high catalytic efficiency (k_cat/K_m) towards DP6 (2571.26 min^-1 mM^-1). The predominant end products from the hydrolysis of locust bean gum, konjac glucomannan and linear MOS are mannobiose and mannotriose. It was observed that KMAN requires at least four binding sites for the binding of substrate molecules and hydrolysis. Molecular docking of mannotriose and galactosyl-mannotetraose to KMAN confirmed its mode of action, which prefers linear substrates to branched substrates.