Purification, characterization, and production of β-mannanase from Bacillus subtilis TJ-102 and its application in gluco-mannooligosaccharides preparation

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.

Enhanced β-mannanase production by Bacillus licheniformis by optimizing carbon source and feeding regimes

Bacillus licheniformis HDYM-04 was isolated in flax retting water and showed β-mannanase activity. Carbon sources for β-mannanase production, as well as the fermentation conditions and feeding strategy, were optimized in shake flasks. When glucose or konjac powder was used as the carbon source, the β-mannanase activity was 288.13 ± 21.59 U/mL and 696.35 ± 23.47 U/mL at 24 h, respectively, which was approximately 4.4- to 10.68-fold higher than the values obtained with wheat powder. When 0.5% (w/v) glucose and 1% (w/v) konjac powder were added together, maximum enzyme activities of 789.07 ± 25.82 U/mL were obtained, an increase of 13.35% compared to the unoptimized cultures with only 1% (w/v) konjac powder. The enzyme activity decreased in the presence of 1% (w/v) konjac powder, but the highest enzyme activity was 1,533.26 ± 33.74 U/mL, a 1.2-fold increase compared with that in nonoptimized cultures; when 0.5% (w/v) glucose was used, the highest enzyme activity was 966.53 ± 27.84 U/mL, an increase in β-mannanase activity of 38.79% compared with control cultures. In this study, by optimizing fed-batch fermentation conditions, the yield of β-mannanase produced by HDYM-04 was increased, laying the foundation for the industrial application and further research of B. licheniformis HDYM-04.

High surfactant-tolerant β-mannanase isolated from Dynastes hercules larvae excrement, and identification of its hotspot using site-directed mutagenesis and molecular dynamics simulations

The β-mannanase from Bacillus subtilis HM7 (Man26HM7) isolated from Dynastes hercules larvae excrement was cloned and expressed in Escherichia coli. Biochemical characterization shows that optimal pH and temperature for catalysis are 6.0 and 50 °C, respectively. Man26HM7 displayed excellent surfactant stability by retaining 70% of initial activity in 1%(w/v) SDS, and more than 90% of initial activity in 1%(w/v) Triton X-100 and Tween 80. Results from amino acid sequence alignment and molecular modeling suggest residue 238 of β-mannanase as a hotspot of SDS-tolerance. Mutagenesis at the equivalent residue of another homolog, β-mannanase from Bacillus subtilis CAe24 (Man26CAe24), significantly enhanced the SDS stability of this enzyme. Comparative computational analysis, including molecular docking and molecular dynamics simulation, were then performed to compute the binding free energy of SDS to Man26HM7, Man26CAe24, and variant enzymes. The results suggest that residue 238 of Man26HM7 is involved in SDS binding to the hydrophobic surface of β-mannanase. This study provides not only the promising application of Man26HM7 in detergent and cleaning products but also valuable information for enhancing the surfactant stability of β-mannanase by enzyme engineering.

Genome-enabled insights into the biology of thrips as crop pests

BACKGROUND

The western flower thrips, Frankliniella occidentalis (Pergande), is a globally invasive pest and plant virus vector on a wide array of food, fiber, and ornamental crops. The underlying genetic mechanisms of the processes governing thrips pest and vector biology, feeding behaviors, ecology, and insecticide resistance are largely unknown. To address this gap, we present the F. occidentalis draft genome assembly and official gene set.

RESULTS

We report on the first genome sequence for any member of the insect order Thysanoptera. Benchmarking Universal Single-Copy Ortholog (BUSCO) assessments of the genome assembly (size = 415.8 Mb, scaffold N50 = 948.9 kb) revealed a relatively complete and well-annotated assembly in comparison to other insect genomes. The genome is unusually GC-rich (50%) compared to other insect genomes to date. The official gene set (OGS v1.0) contains 16,859 genes, of which ~ 10% were manually verified and corrected by our consortium. We focused on manual annotation, phylogenetic, and expression evidence analyses for gene sets centered on primary themes in the life histories and activities of plant-colonizing insects. Highlights include the following: (1) divergent clades and large expansions in genes associated with environmental sensing (chemosensory receptors) and detoxification (CYP4, CYP6, and CCE enzymes) of substances encountered in agricultural environments; (2) a comprehensive set of salivary gland genes supported by enriched expression; (3) apparent absence of members of the IMD innate immune defense pathway; and (4) developmental- and sex-specific expression analyses of genes associated with progression from larvae to adulthood through neometaboly, a distinct form of maturation differing from either incomplete or complete metamorphosis in the Insecta.

CONCLUSIONS

Analysis of the F. occidentalis genome offers insights into the polyphagous behavior of this insect pest that finds, colonizes, and survives on a widely diverse array of plants. The genomic resources presented here enable a more complete analysis of insect evolution and biology, providing a missing taxon for contemporary insect genomics-based analyses. Our study also offers a genomic benchmark for molecular and evolutionary investigations of other Thysanoptera species.

Enhancement of β-Mannanase Production by Bacillus subtilis ATCC11774 through Optimization of Medium Composition

Palm kernel cake (PKC) has been largely produced in Malaysia as one of the cheap and abundant agro-waste by-products from the palm oil industry and it contains high fiber (mannan) content. The present study aimed to produce β-mannanase by Bacillus subtilis ATCC11774 via optimization of the medium composition using palm kernel cake as substrate in semi-solid fermentation. The fermentation nutrients such as PKC, peptone, yeast extract, sodium chloride, magnesium sulphate (MgSO₂), initial culture pH and temperature were screened using a Plackett-Burman design. The three most significant factors identified, PKC, peptone and NaCl, were further optimized using central composite design (CCD), a response surface methodology (RSM) approach, where yeast extract and MgSO₂ were fixed as a constant factor. The maximum β-mannanase activity predicted by CCD under the optimum medium composition of 16.50 g/L PKC, 19.59 g/L peptone, 3.00 g/L yeast extract, 2.72 g/L NaCl and 0.2 g/L MgSO₂ was 799 U/mL. The validated β-mannanase activity was 805.12 U/mL, which was close to the predicted β-mannanas activity. As a comparison, commercial media such as nutrient broth, M9 and Luria bertani were used for the production of β-mannanase with activities achieved at 204.16 ± 9.21 U/mL, 50.32 U/mL and 88.90 U/mL, respectively. The optimized PKC fermentation medium was four times higher than nutrient broth. Hence, it could be a potential fermentation substrate for the production of β-mannanase activity by Bacillus subtilis ATCC11774.

Effects of Mannanoligosaccharide Supplementation on the Growth Performance, Immunity, and Oxidative Status of Partridge Shank Chickens

Mannanoligosaccharides (MOS) can be used in poultry production to modulate immunity and improve growth performance. So, we hypothesized that our enzymatic MOS could achieve the same effects in broilers. To investigate this, a total of 192 one-day-old Partridge Shank chickens were allocated to four dietary treatments consisting of six replicates with eight chicks per replicate, and they were fed a basal diet supplemented with 0, 0.5, 1 and 1.5 g MOS per kg of diet(g/kg) for42 days. Treatments did not affect the growth performance of chickens. Dietary MOS linearly increased the relative weight of the bursa of Fabricius and jejunal immunoglobulin M (IgM) and immunoglobulin G (IgG) content, whereas it linearly decreased cecal Salmonella colonies at 21 days (p < 0.05). The concentration of jejunal secretory immunoglobulin A (sIgA) and IgG at 42 days as well as ileal sIgA, IgG, and IgM at 21 and 42 days were quadratically enhanced by MOS supplementation (p < 0.05). Also, chickens fed MOS exhibited linear and quadratic reduction in jejunal malondialdehyde (MDA) accumulation (p < 0.05). In conclusion, this enzymatic MOS can improve the immune function and intestinal oxidative status of Partridge Shank chickens.

Secretory expression of β-mannanase in Saccharomyces cerevisiae and its high efficiency for hydrolysis of mannans to mannooligosaccharides

Degradation of mannans is a key process in the production of foods and prebiotics. β-Mannanase is the key enzyme that hydrolyzes 1,4-β-D-mannosidic linkages in mannans. Heterogeneous expression of β-mannanase in Pichia pastoris systems is widely used; however, Saccharomyces cerevisiae expression systems are more reliable and safer. We optimized β-mannanase gene from Aspergillus sulphureus and expressed it in five S. cerevisiae strains. Haploid and diploid strains, and strains with constitutive promoter TEF1 or inducible promoter GAL1, were tested for enzyme expression in synthetic auxotrophic or complex medium. Highest efficiency expression was observed for haploid strain BY4741 integrated with β-mannanase gene under constitutive promoter TEF1, cultured in complex medium. In fed-batch culture in a fermentor, enzyme activity reached ~ 24 U/mL after 36 h, and production efficiency reached 16 U/mL/day. Optimal enzyme pH was 2.0-7.0, and optimal temperature was 60 °C. In studies of β-mannanase kinetic parameters for two substrates, locust bean gum galactomannan (LBG) gave K_m = 24.13 mg/mL and V_max = 715 U/mg, while konjac glucomannan (KGM) gave K_m = 33 mg/mL and V_max = 625 U/mg. One-hour hydrolysis efficiency values were 57% for 1% LBG, 74% for 1% KGM, 39% for 10% LBG, and 53% for 10% KGM. HPLC analysis revealed that the major hydrolysis products were the oligosaccharides mannose, mannobiose, mannotriose, mannotetraose, mannopentaose, and mannohexaose. Our findings show that this β-mannanase has high efficiency for hydrolysis of mannans to mannooligosaccharides, a type of prebiotic, suggesting strong potential application in food industries.

A simply enzymatic hydrolysis pretreatment for β-mannanase production from konjac powder

Currently, the traditional fermentation using konjac powder for β-mannanase production presents operational difficulties and high energy consumption, because of the individual hot air sterilization for konjac powder. A simply enzymatic hydrolysis pretreatment for konjac powder was developed to solve the problems of the traditional process in a 7-L fermenter. In the new process, when hydrolysis yield of konjac powder was above 50%, the media became liquid state from gelatinous state and could be sterilized immediately, avoiding the hot air sterilization and solving the operational difficulties. Interestingly, the new process didn't have negative influence on β-mannanase production. Additionally, it could save close to 23% of power consumption during the whole fermentation. For another example, it did work well using locust bean gum for β-mannanase production in a 7-L fermenter. Therefore, the new process might be scaled up for industrial production using mannan-based bioresource as substrate.

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.

Structural and functional analysis of a novel psychrophilic β-mannanase from Glaciozyma antarctica PI12

The structure of a novel psychrophilic β-mannanase enzyme from Glaciozyma antarctica PI12 yeast has been modelled and analysed in detail. To our knowledge, this is the first attempt to model a psychrophilic β-mannanase from yeast. To this end, a 3D structure of the enzyme was first predicted using a threading method because of the low sequence identity (<30%) using MODELLER9v12 and simulated using GROMACS at varying low temperatures for structure refinement. Comparisons with mesophilic and thermophilic mannanases revealed that the psychrophilic mannanase contains longer loops and shorter helices, increases in the number of aromatic and hydrophobic residues, reductions in the number of hydrogen bonds and salt bridges and numerous amino acid substitutions on the surface that increased the flexibility and its efficiency for catalytic reactions at low temperatures.