Selection and characterization of mannanase-producing bacteria useful for the formation of prebiotic manno-oligosaccharides from copra meal

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.

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.

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.

Complete Genome Sequences of Mannanase-Producing Bacillus and Niallia Strains Isolated from the Intestine of the Black Tiger Shrimp (Penaeus monodon)

Here, we report the complete genome sequences of mannanase-producing bacteria, namely, Niallia sp. strain Man26 and Bacillus subtilis strain Man122, isolated from the intestine of Penaeus monodon, the black tiger shrimp. Mannanases are used in various industries, such as food, animal feed, and biorefinery, to hydrolyze mannan to oligomers and mannose.

Enhanced extracellular β-mannanase production by overexpressing PrsA lipoprotein in Bacillus subtilis and optimizing culture conditions

In this study, first, β-mannanase gene man derived from Bacillus amyloliquefaciens CGMCC1.857 was cloned and expressed in Bacillus subtilis 168 to generate B. subtilis M1. However, the extracellular β-mannanase activity of B. subtilis M1 was not very high. To further increase extracellular β-mannanase extracytoplasmic molecular chaperone, PrsA lipoprotein was tandem expressed with man gene in B. subtilis 168 to yield B. subtilis M2. The secretion of β-mannanase of B. subtilis M2 was enhanced by 15.4%, compared with the control B. subtilis M1. Subsequently, process optimization strategies were also developed to enhance β-mannanase production by B. subtilis 168 M2. It was noted that the optimal temperature for β-mannanase production (25°C) was different from the optimal growth temperature (37°C) for B. subtilis. Based on these findings, a two-stage temperature control strategy was proposed where the bacterial culture was maintained at 37°C for the first 12 h to obtain a high rate of cell growth, followed by lowering the temperature to 25°C to enhance β-mannanase production. Using this strategy, the extracellular β-mannanase activity reached 5016 ± 167 U/ml at about 36 h, which was 19.1% greater than the best result obtained using a constant temperature (25°C). The result of this study showed that PrsA lipoprotein overexpression and two-stage temperature control strategy were more efficient for β-mannanase fermentation in B. subtilis.

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.

A randomized trial to evaluate the impact of copra meal hydrolysate on gastrointestinal symptoms and gut microbiome

The impact of copra meal hydrolysate (CMH) on gut health was assessed by conducting a double-blinded, placebo-controlled study. Sixty healthy adult participants, aged 18–40 years were assigned to daily consume 3 g of CMH, 5 g of CMH or placebo in the form of drink powder for 21 days. Consumption of CMH at 3 g/d improved defecating conditions by reducing stool size and also relieved flatulence and bloating symptoms. Fecal samples were collected serially at the baseline before treatment, after the treatment and after a 2-week washout period. The gut microbiomes were similar among the treatment groups, with microbial community changes observed within the groups. Intake of CMH at 3 g/d led to increase microbial diversity and richness. Reduction of the ratio between Firmicutes to Bacteroidetes was observed, although it was not significantly different between the groups. The 3 g/d CMH treatment increased beneficial microbes in the group of fiber-degrading bacteria, especially human colonic Bacteroidetes, while induction of Bifidobacteriaceae was observed after the washout period. Intake of CMH led to increase lactic acid production, while 3 g/d supplement promoted the present of immunoglobulin A (IgA) in stool samples. The 3 g daily dose of CMH led to the potentially beneficial effects on gut health for healthy individuals.

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.

Production of manno-oligosaccharide from Gleditsia microphylla galactomannan using acetic acid and ferrous chloride

A novel and efficient method for manno-oligosaccharides (MOS) production has been proposed by utilizing Gleditsia microphylla galactomannan as the starting material. This co-operative hydrolysis using ferrous chloride (Fe²⁺) and acetic acid (HAc) effectively improved the MOS yield and meanwhile decreased the amount of monosaccharide and the 5-hydroxymethyl-furfural (HMF). The highest yields under the optimum conditions were 46.7% by HAc hydrolysis (5 M HAc at 130 °C for 120 min); 37.3% by Fe²⁺ hydrolysis (0.1 M Fe²⁺ at 150 °C for 120 min); and 51.4% by co-operative hydrolysis (2 M HAc, 0.05 M Fe²⁺ at 160 °C for 10 min). From the changes in the value of M/G (mannose/galactose) ratios, it was deduced that Fe²⁺ predominantly cleaves the main chain, and HAc assists in the breakage of the side chain, thus resulting in the high-efficient co-operative hydrolysis for the production of MOS.

Applications of Microbial β-Mannanases

Mannans are main components of hemicellulosic fraction of softwoods and they are present widely in plant tissues. β-mannanases are the major mannan-degrading enzymes and are produced by different plants, animals, actinomycetes, fungi, and bacteria. These enzymes can function under conditions of wide range of pH and temperature. Applications of β-mannanases have therefore, been found in different industries such as animal feed, food, biorefinery, textile, detergent, and paper and pulp. This review summarizes the most recent studies reported on potential applications of β-mannanases and bioengineering of β-mannanases to modify and optimize their key catalytic properties to cater to growing demands of commercial sectors.

Prebiotic mannooligosaccharides: Synthesis, characterization and bioactive properties

Functional oligosaccharides are non-digestible food ingredients that confer numerous health benefits. Among these, mannooligosaccharides (MOS) are emerging prebiotics that have characteristic potential bio-active properties. Microbial mannanases can be used to break down mannan rich agro-residues to yield MOS. Various applications of MOS as health promoting functional food ingredient may open up newer opportunities in food and feed industry. Enzymatic hydrolysis is the widely preferred method over chemical hydrolysis for MOS production. Presently, commercial MOS is being derived from yeast cell wall mannan and is widely used as prebiotic in feed supplements for poultry and aquaculture. Apart from stimulating the growth of probiotic microflora, MOS impart anticancer and immunomodulatory effects by inducing different gene markers in colon cells. This review summarizes recent developments and future prospects of enzymatic synthesis of MOS from various mannans, their structural characteristics and their potential health benefits.

Expression, Characterization and Structure Analysis of a New GH26 Endo-β-1, 4-Mannanase (Man26E) from Enterobacter aerogenes B19

β-mannanase is one of the key enzymes to hydrolyze hemicellulose. At present, most β-mannanases are not widely applied because of their low enzyme activity and unsuitable enzymatic properties. In this work, a new β-mannanase from Enterobacter aerogenes was studied, which laid the foundation for its further application. Additionally, we will further perform directed evolution of the enzyme to increase its activity, improve its temperature and pH properties to allow it more applications in industry. A new β-mannanase (Man26E) from Enterobacter aerogenes was successfully expressed in Escherichia coli. Man26E showed about 40 kDa on SDS-PAGE gel. The SWISS-MODEL program was used to model the tertiary structure of Man26E, which presented a core (α/β)8-barrel catalytic module. Based on the binding pattern of CjMan26 C, Man26E docking Gal1Man4 was investigated. The catalytic region consisted of a surface containing four solvent-exposed aromatic rings, many hydrophilic and charged residues. Man26E displayed the highest activity at pH 6.0 and 55 °C, and high acid and alkali stability in a wide pH range (pH 4–10) and thermostability from 40 to 50 °C. The enzyme showed the highest activity on locust bean gum, and the Km and Vmax were 7.16 mg mL−1 and 508 U mg−1, respectively. This is the second β-mannanase reported from Enterobacter aerogenes B19. The β-mannanase displayed high enzyme activity, a relatively high catalytic temperature and a broad range of catalytic pH values. The enzyme catalyzed both polysaccharides and manno-oligosaccharides.

Expression, homology modeling and enzymatic characterization of a new β-mannanase belonging to glycoside hydrolase family 1 from Enterobacter aerogenes B19

BACKGROUND

β-mannanase can hydrolyze β-1,4 glycosidic bond of mannan by the manner of endoglycosidase to generate mannan-oligosaccharides. Currently, β-mannanase has been widely applied in food, medicine, textile, paper and petroleum exploitation industries. β-mannanase is widespread in various organisms, however, microorganisms are the main source of β-mannanases. Microbial β-mannanases display wider pH range, temperature range and better thermostability, acid and alkali resistance, and substrate specificity than those from animals and plants. Therefore microbial β-mannanases are highly valued by researchers. Recombinant bacteria constructed by gene engineering and modified by protein engineering have been widely applied to produce β-mannanase, which shows more advantages than traditional microbial fermentation in various aspects.

RESULTS

A β-mannanase gene (Man1E), which encoded 731 amino acid residues, was cloned from Enterobacter aerogenes. Man1E was classified as Glycoside Hydrolase family 1. The bSiteFinder prediction showed that there were eight essential residues in the catalytic center of Man1E as Trp166, Trp168, Asn229, Glu230, Tyr281, Glu309, Trp341 and Lys374. The catalytic module and carbohydrate binding module (CBM) of Man1E were homologously modeled. Superposition analysis and molecular docking revealed the residues located in the catalytic module of Man1E and the CBM of Man1E. The recombinant enzyme was successfully expressed, purified, and detected about 82.5 kDa by SDS-PAGE. The optimal reaction condition was 55 °C and pH 6.5. The enzyme exhibited high stability below 60 °C, and in the range of pH 3.5-8.5. The β-mannanase activity was activated by low concentration of Co²⁺, Mn²⁺, Zn²⁺, Ba²⁺ and Ca²⁺. Man1E showed the highest affinity for Locust bean gum (LBG). The K_m and V_max values for LBG were 3.09 ± 0.16 mg/mL and 909.10 ± 3.85 μmol/(mL min), respectively.

CONCLUSIONS

A new type of β-mannanase with high activity from E. aerogenes is heterologously expressed and characterized. The enzyme belongs to an unreported β-mannanase family (CH1 family). It displays good pH and temperature features and excellent catalysis capacity for LBG and KGM. This study lays the foundation for future application and molecular modification to improve its catalytic efficiency and substrate specificity.

Cultivation of Mushrooms and Their Lignocellulolytic Enzyme Production Through the Utilization of Agro-Industrial Waste

A large amount of agro-industrial waste is produced worldwide in various agricultural sectors and by different food industries. The disposal and burning of this waste have created major global environmental problems. Agro-industrial waste mainly consists of cellulose, hemicellulose and lignin, all of which are collectively defined as lignocellulosic materials. This waste can serve as a suitable substrate in the solid-state fermentation process involving mushrooms. Mushrooms degrade lignocellulosic substrates through lignocellulosic enzyme production and utilize the degraded products to produce their fruiting bodies. Therefore, mushroom cultivation can be considered a prominent biotechnological process for the reduction and valorization of agro-industrial waste. Such waste is generated as a result of the eco-friendly conversion of low-value by-products into new resources that can be used to produce value-added products. Here, we have produced a brief review of the current findings through an overview of recently published literature. This overview has focused on the use of agro-industrial waste as a growth substrate for mushroom cultivation and lignocellulolytic enzyme production.

Nutritional improvement of copra meal using mannanase and Saccharomyces cerevisiae

Copra meal is a by-product of coconut milk extraction, contained 4.60 ± 0.01 g/100 g DM and 62.19 ± 0.53% of protein and fiber, respectively. The optimal condition for quality improvement of copra meal was investigated using Box-Behnken design combined with response surface methodology (RSM). The simultaneous saccharification and fermentation (SSF) of Copra meal was performed by mannanase enzyme and yeast, Saccharomyces cerevisiae. The concentration of mannanase was determined as the most important factor to increase protein content in copra meal. The protein content was increased by 64% when 0.7% of enzyme per copra meal dry weight, the ratio of copra meal to water at 1:4.56 and fermentation time of 90.25 h at 30 °C were used. The program predicted an increase of 3.06 g of protein/100 g dry matter; however, the experimental result showed an increase of 3.35 g/100 g DM of protein in copra meal. The 10 kg of copra meal SSF in Koji reactor, the protein content increased to 4.18 g/100 g DM, while fiber content decreased 49%. Moreover, amino acids were increased by 64.05% and oligosaccharides, especially mannohexaose, were increased to 0.708 g/g DM. Results showed that fermentation of copra meal with mannanase and yeast offers a potential method to improve the nutrition of copra meal as animal feed.

In vitro fermentation of copra meal hydrolysate by human fecal microbiota

Copra meal hydrolysate (CMH) is obtained by hydrolyzing defatted copra meal with β-mannanase from Bacillus circulans NT 6.7. In this study, we investigated the resistance of CMH to upper gastrointestinal tract digestion and the fecal fermentation profiles of CMH. Fecal slurries from four healthy human donors were used as inocula, and fructooligosaccharides (FOS) were used as a positive prebiotic control. Fecal batch cultures were performed at 37 °C under anaerobic conditions. Samples were collected at 0, 10, 24 and 34 h for bacterial enumeration via fluorescent in situ hybridization and organic acid (OA) analysis. In vitro gastric stomach and human pancreatic α-amylase simulations demonstrated that CMH was highly resistant to hydrolysis. Acetate was the main fermentation product of all the substrates. The proportions of acetate production of the total OAs from FOS, CMH and yeast mannooligosaccharides (MOS) after 34 h of fermentation did not significantly differ (69.76, 65.24 and 53.93%, respectively). At 24 h of fermentation, CMH promoted the growth of Lactobacillus and Bifidobacterium groups (P < 0.01) and did not significantly differ from the results obtained using FOS. The results of in vitro fecal fermentation of CMH indicate that CMH can promote the growth of beneficial bacteria.

Characterization and high-efficiency secreted expression in Bacillus subtilis of a thermo-alkaline β-mannanase from an alkaliphilic Bacillus clausii strain S10

Background

β-Mannanase catalyzes the cleavage of β-1,4-linked internal linkages of mannan backbone randomly to produce new chain ends. Alkaline and thermostable β-mannanases provide obvious advantages for many applications in biobleaching of pulp and paper, detergent industry, oil grilling operation and enzymatic production of mannooligosaccharides. However, only a few of them are commercially exploited as wild or recombinant enzymes, and none heterologous and secretory expression of alkaline β-mannanase in Bacillus subtilis expression system was reported. Alkaliphilic Bacillus clausii S10 showed high β-mannanase activity at alkaline condition. In this study, this β-mannanase was cloned, purified and characterized. The high-level secretory expression in B. subtilis was also studied.

Results

A thermo-alkaline β-mannanase (BcManA) gene encoding a 317-amino acid protein from alkaliphilic Bacillus clausii strain was cloned and expressed in Escherichia coli. The purified mature BcManA exhibited maximum activity at pH 9.5 and 75 °C with good stability at pH 7.0–11.5 and below 80 °C. BcManA demonstrated high cleavage capability on polysaccharides containing β-1,4-mannosidic linkages, such as konjac glucomannan, locust bean gum, guar gum and sesbania gum. The highest specific activity of 2366.2 U mg⁻¹ was observed on konjac glucomannan with the K_m and k_cat value of 0.62 g l⁻¹ and 1238.9 s⁻¹, respectively. The hydrolysis products were mainly oligosaccharides with a higher degree of polymerization than biose. BcManA also cleaved manno-oligosaccharides with polymerization degree more than 3 without transglycosylation. Furthermore, six signal peptides and two strong promoters were used for efficiently secreted expression optimization in B. subtilis WB600 and the highest extracellular activity of 2374 U ml⁻¹ with secretory rate of 98.5% was obtained using SP_lipA and P43 after 72 h cultivation in 2 × SR medium. By medium optimization using cheap nitrogen and carbon source of peanut meal and glucose, the extracellular activity reached 6041 U ml⁻¹ after 72 h cultivation with 6% inoculum size by shake flask fermentation.

Conclusions

The thermo-alkaline β-mannanase BcManA showed good thermal and pH stability and high catalytic efficiency towards konjac glucomannan and locust bean gum, which distinguished from other reported β-mannanases and was a promising thermo-alkaline β-mannanase for potential industrial application. The extracellular BcManA yield of 6041 U ml⁻¹, which was to date the highest reported yield by flask shake, was obtained in B. subtilis with constitutive expression vector. This is the first report for secretory expression of alkaline β-mannanase in B. subtilis protein expression system, which would significantly cut down the production cost of this enzyme. Also this research would be helpful for secretory expression of other β-mannanases in B. subtilis.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0973-0) contains supplementary material, which is available to authorized users.

Optimization of enzymatic hydrolysis of copra meal: compositions and properties of the hydrolysate

This study demonstrated that oligosaccharides from copra meal could be prepared by using a commercial enzyme preparation containing mannanase for use as a prebiotic. The conditions giving the highest hydrolysis rate of the copra meal by the enzyme were pH 4 and temperature of 40 °C with an enzyme to substrate ratio (E/S) of 1092.69 β-mannanase activity unit/g of the dried copra meal. Monosaccharide was the predominant product of the hydrolysis reaction followed by di- and tri-saccharide. Activated carbon treatment of the copra meal hydrolysate reduced the monosaccharide content resulting in 36.13% of monosaccharide, 54.26% of disaccharide and 9.61% of trisaccharide. All monosaccharides were eliminated by incubating the copra meal hydrolysate with Saccharomyces cerevisiae for 48 h, which promoted the growth of B. breve, L. plantrarum, B. bifidum, L. bugaricus, L. acidophilus, L. brevis, L. casei, B. longum, and S. thermophiles while retarding the growth of the pathogenic bacteria, S. aureus and E. coli.

Optimization of hydrolysis conditions for the mannooligosaccharides copra meal hydrolysate production

Copra meal is a good source of galactomannan and its mannooligosaccharides have prebiotic properties. However, limited data are available concerning the ideal requirements for mannan hydrolysis. Thus, optimum hydrolysis conditions for the production of oligosaccharides from copra meal hydrolysate were investigated using response surface methodology. Model validation provided good agreement between experimental results and predicted responses. Maximum oligosaccharide of 14.41 ± 0.09 mg/ml (20 ml) was obtained at an enzyme concentration of 16.52 U/ml, substrate concentration 15% and reaction time 12 h. On a larger scale, this increased to 15.76 ± 0.04 mg/ml (200 ml) and 16.89 mg/ml (2000 ml). Defatted copra meal hydrolysate promoted the growth of beneficial bacteria as lactobacilli and bifidobacteria, while inhibiting pathogens Salmonella serovar Enteritidis S003, Escherichia coli E010, Staphylococcus aureus TISTR 029 and Shigella dysenteriae DMST 1511. Higher yield of oligosaccharides under optimum conditions indicated the potential of this method for production of mannooligosaccharides from copra meal hydrolysate on an industrial scale.

Kinetic properties analysis of beta-mannanase from Klebsiella oxytoca KUB-CW2-3 expressed in Escherichia coli

Endo-1,4-β-mannanase is an enzyme that can catalyze the random hydrolysis of β-1,4-mannosidic linkages in the main chain of mannans, glucomannans and galactomannans and offers many applications in different biotechnology industries. Purification and kinetic properties of the endo-1,4-β-mannanase from recombinant Escherichia coli strain KMAN-3 were examined. Recombinant β-mannanase (KMAN-3) was purified 50.5 fold using Ni-NTA Agarose resin and specific activity of 11900 U/mg protein was obtained. Purified KMAN-3 showed a single band on SDS-PAGE with a molecular weight of 43 kDa. K_m and V_max values of KMAN-3 on ivory nut mannan, locust bean gum, defatted copra meal and konjac glucomannan were 243, 3.83 × 10⁵ 37 and 2.13 × 10⁶ mg ml^-1 and 2940, 61,100, 3930 and 1.56 × 10¹⁰ mg^-1, respectively. Carboxymethyl cellulose was not digested by KMAN-3.

In vitro fermentation of copra meal hydrolysate by chicken microbiota

The aim of this study was to carry out preliminary investigations on the in vitro fermentation selectivity of copra meal hydrolysate (CMH) by chicken gut microbiota. The ileum and cecum contents from three 35-day-old birds were used as inocula. Yeast mannooligosaccharide (yeast-MOS) or α-mannan was selected as a positive control. Batch culture fermentation with fecal bacteria was performed at 42 °C for 24 h in an anaerobic chamber. Samples were collected at 0, 6, 12, 18 and 24 h of fermentation and evaluated using real-time PCR and short-chain fatty acid (SCFA) analysis. Results showed that the medium containing ileum and both CMH and yeast-MOS substrates led to an increase in the growth of the dominant groups as Lactobacillus, Enterobacteriaceae and Enterococcus spp. compared with 0-h fermentation. Campylobacter spp. and Bifidobacterium spp. were not detected in any samples. A significant decrease in Acinetobacter was observed in all substrates tested after 6 h of fermentation (P < 0.05). Only the sample from CMH fermentation showed a significantly greater reduction in the population of Pseudomonas after 18-h fermentation with ileum content (P < 0.05). Propionate was the main fermentation product found in both ileum and cecum fermentation followed by lactate and acetate. CMH can be utilized by ileum and cecum microbial of chickens, and CMH has a generally desirable effect on the microbiota. CMH has the potential for use as a supplementary diet with similar or improved benefits and lower costs compared to commercial prebiotics. Further experiments in animal trials would seem to be justified.

Characterization of pH-tolerant and thermostable GH 134 β-1,4-mannanase SsGH134 possessing carbohydrate binding module 10 from Streptomyces sp. NRRL B-24484

A GH 134 β-1,4-mannanase SsGH134 from Streptomyces sp. NRRL B-24484 possesses a carbohydrate binding module (CBM) 10 and a glycoside hydrolase 134 domain at the N- and C-terminal regions, respectively. Recombinant SsGH134 expressed in Escherichia coli. SsGH134 was maximally active within a pH range of 4.0-6.5 and retained >80% of this maximum after 90 min at 30°C within a pH range of 3.0-10.0. The β-1,4-mannanase activity of SsGH134 towards glucomannan was 30% of the maximal activity after an incubation at 100°C for 120 min, indicating that SsGH134 is pH-tolerant and thermostable β-1,4-mannanase. SsGH134, SsGH134-ΔCBM10 (CBM10-linker-truncated SsGH134) and SsGH134-G34W (substitution of Gly34 to Trp) bound to microcrystalline cellulose, β-mannan and chitin, regardless of the presence or absence of CBM10. These indicate that GH 134 domain strongly bind to the polysaccharides. Although deleting CBM10 increased the catalytic efficiency of the β-1,4-mannanase, its disruption decreased the pH, solvent and detergent stability of SsGH134. These findings indicate that CBM10 inhibits the β-1,4-mannanase activity of SsGH134, but it is involved in stabilizing its enzymatic activity within a neutral-to-alkaline pH range, and in the presence of various organic solvents and detergents. We believe that SsGH134 could be useful to a diverse range of industries.

Manufacture and Properties of Glucomannans and Glucomannooligosaccharides Derived from Konjac and Other Sources

Glucomannans (GM) are polymers that can be found in natural resources, such as tubers, bulbs, roots, and both hard- and softwoods. In fact, mannan-based polysaccharides represent the largest hemicellulose fraction in softwoods. In addition to their structural functions and their role as energy reserve, they have been assessed for their healthy applications, including their role as new source of prebiotics. This paper summarizes the scientific literature regarding the manufacture and functional properties of GM and their hydrolysis products with a special focus on their prebiotic activity.

Purification and Characterization of a Thermostable β-Mannanase from Bacillus subtilis BE-91: Potential Application in Inflammatory Diseases

β-mannanase has shown compelling biological functions because of its regulatory roles in metabolism, inflammation, and oxidation. This study separated and purified the β-mannanase from Bacillus subtilis BE-91, which is a powerful hemicellulose-degrading bacterium using a "two-step" method comprising ultrafiltration and gel chromatography. The purified β-mannanase (about 28.2 kDa) showed high specific activity (79, 859.2 IU/mg). The optimum temperature and pH were 65°C and 6.0, respectively. Moreover, the enzyme was highly stable at temperatures up to 70°C and pH 4.5-7.0. The β-mannanase activity was significantly enhanced in the presence of Mn²⁺, Cu²⁺, Zn²⁺, Ca²⁺, Mg²⁺, and Al³⁺ and strongly inhibited by Ba²⁺ and Pb²⁺. K_m and V_max values for locust bean gum were 7.14 mg/mL and 107.5 μmol/min/mL versus 1.749 mg/mL and 33.45 µmol/min/mL for Konjac glucomannan, respectively. Therefore, β-mannanase purified by this work shows stability at high temperatures and in weakly acidic or neutral environments. Based on such data, the β-mannanase will have potential applications as a dietary supplement in treatment of inflammatory processes.

Molecular cloning of kman coding for mannanase from Klebsiella oxytoca KUB-CW2-3 and its hybrid mannanase characters

Gene encoding for β-mannanase (E.C 3.2.1.78) from Klebsiella oxytoca KUB-CW2-3 was cloned and expressed by an E. coli system resulting in 400 times higher mannanase activities than the wild type. A 3314bp DNA fragment obtained revealed an open reading frame of 1164bp, namely kman-2, which encoded for 387 amino acids with an estimated molecular weight of 43.2kDa. It belonged to the glycosyl hydrolase family 26 (GH26) exhibited low similarity of 50-71% to β-mannanase produced by other microbial sources. Interestingly, the enzyme had a broad range of substrate specificity of homopolymer of ivory nut mannan (6%), carboxymethyl cellulose (30.6%) and avicel (5%), and heteropolymer of konjac glucomannan (100%), locust bean gum (92.6%) and copra meal (non-defatted 5.3% and defatted 7%) which would be necessary for in vivo feed digestion. The optimum temperature and pH were 30-50°C and 4-6, respectively. The enzyme was still highly active over a low temperature range of 10-40°C and over a wide pH range of 4-10. The hydrolysates of konjac glucomannan (H-KGM), locust bean gum (H-LBG) and defatted copra meal (H-DCM) composed of compounds which were different in their molecular weight range from mannobiose to mannohexaose and unknown oligosaccharides indicating the endo action of mannanase. Both H-DCM and H-LBG enhanced the growth of lactic acid bacteria and some pathogens except Escherichia coli E010 with a specific growth rate of 0.36-0.83h(-1). H-LBG was more specific to 3 species of Weissella confusa JCM 1093, Lactobacillus reuteri KUB-AC5, Lb salivarius KL-D4 and E. coli E010 while both H-KGM and H-DCM were to Lb. reuteri KUB-AC5 and Lb. johnsonii KUNN19-2. Based on the nucleotide sequence of kman-2 containing two open reading frames of 1 and 2at 5' end of the +1 and +43, respectively, removal of the first open reading frame provided the recombinant clone E. coli KMAN-3 resulting in the mature protein of mannanase composing of 345 amino acid residues confirmed by 3D structure analysis and amino acid sequence at N-terminal namely KMAN (GenBank accession number KM100456). It exhibited 10 times higher extracellular and periplasmic total activities of 17,600 and 14,800 units than E. coli KMAN-2. With its low similarity to mannanases previously proposed, wide range of homo- and hetero-polysaccharide specificity, negative effect to E. coli and most importance of high production, it would be proposed as a novel mannanase source for application in the future.

Characterization of mannanase from Bacillus circulans NT 6.7 and its application in mannooligosaccharides preparation as prebiotic

This study focused on the characterization of mannanase from Bacillus circulans NT 6.7 for mannooligosaccharides (MOS) production. The enzyme from B. circulans NT 6.7 was produced using defatted copra meal as a carbon source. The mannanase was purified by ultrafiltration and column chromatography of Q-Sepharose. The purified protein (M1) was a dimeric protein with a 40 kDa subunit. The purified M1 exhibited optimum pH and temperature at pH 6.0 and 60 °C, respectively. It was activated by Mn(2+,) Mg(2+,) and Cu(2+), and as inhibited by EDTA (45-65 %). The purified enzyme exhibited high specificity to beta-mannan: konjac (glucomannan), locust bean gum (galactomannan), ivory nut (mannan), guar gum (galactomannan) and defatted copra meal (galactomannan). The defatted copra meal could be hydrolyzed by purified M1 into mannooligosaccharides which promoted beneficial bacteria, especially Lactobacillus group, and inhibited pathogenic bacteria; Shigella dysenteria DMST 1511, Staphylococcus aureus TISTR 029, and Salmonella enterica serovar Enteritidis DMST 17368. Therefore, the mannanase from B. circulans NT 6.7 would be a novel source of enzymes for the mannooligosaccharides production as prebiotics.

A β-mannanase from Paenibacillus sp.: Optimization of production and its possible prebiotic potential

A thermotolerant bacterium Paenibacillus thiaminolyticus with an ability to produce extracellular β-mannanase was isolated from a soil sample. Bacterium produced 45 U/mL β-mannanase at 50 °C. The culture conditions for high-level production of β-mannanase were optimized. Optimized MS medium [wheat bran 2% (w/v), ammonium sulfate 0.3% (w/v), yeast extract, and peptone (0.025% each) pH 6.5] was inoculated with 2% of 16 H old culture.  The culture was incubated at 50 °C for 48 H resulting in 24-folds higher β-mannanase production (1,100 ± 50 U/mL). Optimum pH and temperature for enzyme activity of the crude enzyme was 6.0 and 60 °C, respectively. The enzyme demonstrated 65% relative enzyme activity at 37 °C. The hydrolytic activity of the crude enzymatic preparation was assessed on various agro residues. Thin-layer chromatographic analysis showed that the enzyme activity to saccharify heteromannans resulted in production of a mixture of manno-oligosaccharides (MOS) and enzyme exhibited classic endo-activity. To evaluate the possible prebiotic potential of the MOS thus obtained, initial screening for their ability to support the growth of probiotics was carried out by the pure culture method. Bifidobacterium and Lactobacillus sp. responded positively to the addition of enzymatically derived oligosaccharides and their numbers increased significantly.

Improved Mannanase Production from Penicillium occitanis by Fed-Batch Fermentation Using Acacia Seeds

By applying a fed-batch strategy, production of Penicillium occitanis mannanases could be almost doubled as compared to a batch cultivation on acacia seeds (76 versus 41 U/mL). Also, a 10-fold increase of enzyme activities was observed from shake flask fermentation to the fed-batch fermentation. These production levels were 3-fold higher than those obtained on coconut meal. The high mannanase production using acacia seeds powder as inducer substrate showed the suitability of this culture process for industrial-scale development.

Expression of Bacillus subtilis MA139 beta-mannanase in Pichia pastoris and the enzyme characterization

The 1014 nucleotides long gene-encoding beta-mannanase from Bacillus subtilis strain MA139 was cloned using PCR. To obtain high expression levels in Pichia pastoris, the beta-mannanase gene was optimized according to the codon usage bias of P. pastoris and fused downstream of GAP promoter. The reconstituted plasmid pGAP-mann was transformed into P. pastoris X-33 strain to constitutively express beta-mannanase. When cultured at 28 degrees Celsius for 3 days protein yields up to 2.7 mg/mL was obtained with the enzyme activity of up to 230 U/mL. In comparison, wild-type gene product yielded 1.9 mg/mL and 170 U/mL, respectively indicating that the protein yield and enzyme activity were significantly improved by codon modification. After purification, the enzyme properties were characterized. The optimal activity was at pH 6.0 and 50 degrees Celsius. In the pH range of 3.0 to 9.0, beta-mannanase showed above 60% of its peak activity. Among the numerous ions tested copper significantly inhibited the enzyme activity. These results suggested that codon-optimized beta-mannanase expressed in P. pastoris could potentially be used as an additive in the feed for monogastric animals.