Purification and characterization of chitosanase from Bacillus sp. strain KCTC 0377BP and its application for the production of chitosan oligosaccharides

Expression of chitosanase from Aspergillus fumigatus chitosanase in Saccharomyces cerevisiae by CRISPR-Cas9 tools

Chitooligosaccharides (COS) find numerous applications due to their exceptional properties. Enzymatic hydrolysis of chitosan by chitosanase is considered an advantageous route for COS production. Heterologous expression of chitosanase holds significant promise, yet studies using commonly employed Escherichia coli and Pichia pastoris strains encounter challenges in subsequent handling and industrial scalability. In this investigation, we opted for using the safe yeast strain Saccharomyces cerevisiae (GRAS), obviating the need for methanol induction, resulting in successful expression. Ultimately, utilizing the GTR-CRISPR editing system, shake flask enzyme activity reached 2 U/ml. The optimal chitosanase activity was achieved at 55℃ and pH 5, with favorable stability between 30 and 50 °C. Following a 2-h catalytic reaction, the product primarily consisted of chitobiose to chitotetraose, predominantly at the chitotriose position, with a slight increase in chitobiose content observed during the later stages of enzymatic hydrolysis. The results affirm the feasibility of heterologous chitosanase expression through Saccharomyces cerevisiae, underscoring its significant industrial potential.

Chitooligosaccharide and Its Derivatives: Potential Candidates as Food Additives and Bioactive Components

Chitooligosaccharide (CHOS), a depolymerized chitosan, can be prepared via physical, chemical, and enzymatic hydrolysis, or a combination of these techniques. The superior properties of CHOS have attracted attention as alternative additives or bioactive compounds for various food and biomedical applications. To increase the bioactivities of a CHOS, its derivatives have been prepared via different methods and were characterized using various analytical methods including FTIR and NMR spectroscopy. CHOS derivatives such as carboxylated CHOS, quaternized CHOS, and others showed their potential as potent anti-inflammatory, anti-obesity, neuroprotective, and anti-cancer agents, which could further be used for human health benefits. Moreover, enhanced antibacterial and antioxidant bioactivities, especially for a CHOS-polyphenol conjugate, could play a profound role in shelf-life extension and the safety assurance of perishable foods via the inhibition of spoilage microorganisms and pathogens and lipid oxidation. Also, the effectiveness of CHOS derivatives for shelf-life extension can be augmented when used in combination with other preservative technologies. Therefore, this review provides an overview of the production of a CHOS and its derivatives, as well as their potential applications in food as either additives or nutraceuticals. Furthermore, it revisits recent advancements in translational research and in vivo studies on CHOS and its derivatives in the medical-related field.

Chitosanase Production from the Liquid Fermentation of Squid Pens Waste by Paenibacillus elgii

Chitosanases play a significant part in the hydrolysis of chitosan to form chitooligosaccharides (COS) that possess diverse biological activities. This study aimed to enhance the productivity of Paenibacillus elgii TKU051 chitosanase by fermentation from chitinous fishery wastes. The ideal parameters for achieving maximum chitosanase activity were determined: a squid pens powder amount of 5.278% (w/v), an initial pH value of 8.93, an incubation temperature of 38 °C, and an incubation duration of 5.73 days. The resulting chitosanase activity of the culture medium was 2.023 U/mL. A chitosanase with a molecular weight of 25 kDa was isolated from the culture medium of P. elgii TKU051 and was biochemically characterized. Liquid chromatography with tandem mass spectrometry analysis revealed that P. elgii TKU051 chitosanase exhibited a maximum amino acid identity of 43% with a chitosanase of Bacillus circulans belonging to the glycoside hydrolase (GH) family 46. P. elgii TKU051 chitosanase demonstrated optimal activity at pH 5.5 while displaying remarkable stability within the pH range of 5.0 to 9.0. The enzyme displayed maximum efficiency at 60 °C and demonstrated considerable stability at temperatures ≤40 °C. The presence of Mn2+ positively affected the activity of the enzyme, while the presence of Cu2+ had a negative effect. Thin-layer chromatography analysis demonstrated that P. elgii TKU051 chitosanase exhibited an endo-type cleavage pattern and hydrolyzed chitosan with 98% degree of deacetylation to yield (GlcN)2 and (GlcN)3. The enzymatic properties of P. elgii TKU051 chitosanase render it a promising candidate for application in the production of COS.

Production, statistical evaluation and characterization of chitosanase from Fusarium oxysporum D18

Purpose

The present research work focuses on the extraction of chitosanase enzyme from soil fungi. Chitosan hydrolysis by chitosanase is one of the most effective methods to produce chitosan oligosaccharides which are new biomaterials that have many biological activities such as antitumour, antioxidant, antidiabetic and antimicrobial.

Method

A strain producing chitosanase was screened and identified as Fusarium oxysporum D18 with an accession number OL343607. Various physiological parameters (incubation type, carbon source, additive nitrogen source, statistical evaluation, solid state fermentation) were assessed to increase chitosanase production.

Results

Fusarium oxysporum D18 produced a considerable value of chitosanase (1.220 U/ml). After 7 days of incubation, the best carbon source was lactose, and the best nitrogen source was ammonium chloride. Statistical evaluation was carried out by using Plackett–Burman and Box-Behnken designs. The highest chitosanase production (1.994 U/ml) was induced by the medium composition g/l: KH2PO4 (1.5), MgSO4 (0.269), lactose (18), NH4Cl (1.26), pH (6.68), using a 5-day-old inoculum and chitosanase activity was 1.63 folds that of the original medium. The production of chitosanase by Fusarium oxysporum D18 in solid state cultures using different solid substrates was studied and the best solid substrate for higher chitosanase activity (2.246 U/ml) was raw shrimp heads and shells and chitosanase activity was 1.13 folds that of the optimized liquid cultures. An extracellular chitosanase was isolated and partially purified by using 75% saturation of ammonium sulphate. The highest chitosanase activity (3.667 U/ml) with a specific activity of 0.390 U/mg protein was obtained at enzyme protein concentration of 9.391 mg/ml, substrate concentration of 1.2 % (w/v), Vmax of the enzyme of approximately 0.430 U/mg protein, and KM of 0.26 % (w/v), at pH 5.6 and reaction temperature of 50 °C. The activity of the purified and characterized chitosanase increased by 3 times than that the original isolate activity. The enzyme was thermostable and retained about 55% of its original activity after heating at 70 °C for 15 min. The enzyme preparations were activated by Ca2+ ions and inactivated by Zn+2, Cu+2 ions, and EDTA.

Conclusion

An antitumour activity of chitooligosaccharides produced by the chitosanase was applied to the MCF-7 (breast carcinoma cells) and they had a cytotoxicity inhibitory effect against them about IC50 = 448 μg/ml.

Production, Statistical Evaluation and Characterization of Chitosanase from Fusarium oxysporum D18.. [DOI: 10.21203/rs.3.rs-2898996/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Purpose The present research work focuses on the extraction of chitosanase enzyme from soil fungi. Chitosan hydrolysis by chitosanase is one of the most effective methods to produce chitosan oligosaccharides which are new biomaterials that have many biological activities such as antitumor, antioxidant, antidiabetic and antimicrobial. Method: A strain producing chitosanase was screened and identified as Fusarium oxysporum D18 with an accession number OL343607. Various physiological parameters (incubation type, carbon source, additive nitrogen source, statistical evaluation, solid state fermentation) were assessed to increase chitosanase production. Results: Fusarium oxysporum D18 produced a considerable value of chitosanase, (1.220 U/ml). after 7 days of incubation, the best carbon source was lactose, and the best nitrogen source was ammonium chloride. Statistical evaluation was carried out by using Plackett-Burman and Box-Behnken designs. The highest chitosanase production, (1.994 U/ml) was induced by the medium composition g/L: KH2PO4 (1.5), MgSO4 (0.269), lactose (18), NH4Cl (1.26), pH (6.68), using a 5-day old inoculum and chitosanase activity was 1.63 folds that of the original medium. The production of chitosanase by Fusarium oxysporum D18 in solid state cultures using different solid substrates was studied and the best solid substrate for higher chitosanase activity (2.246 U/ml) was raw shrimp heads and shells and chitosanase activity was 1.13 folds that of the optimized liquid cultures. An extracellular chitosanase was isolated and partially purified by using 75 % saturation of ammonium sulphate. The highest chitosanase activity (3.667 U/ml) was obtained at enzyme protein concentration, (9.391 mg/ml), substrate concentration, (1.20%), Vmax of the enzyme was approximately (4.04 U/ml), km was (0.26%), at pH, (5.6) and reaction temperature, (50°C). The activity of the purified and characterized chitosanase increased by 3 times than that the original isolate activity. The enzyme was thermostable and retained about 55% of its original activity after heating at 70°C for 15 min. The enzyme preparations were activated by Ca2+ ions and inactivated by Zn+2, Cu+2 ions, and EDTA. Conclusion: An antitumor activity of chitooligosaccharides produced by the chitosanase was applied to the MCF-7 (breast carcinoma cells) and they had a cytotoxicity inhibitory effect against them about IC50 = (448 μg/ml).

Characterization of different chitosanases of Bacillus strains and their application in chitooligosaccharides production

Chitosanases are potential candidates for chitooligosaccharides (COS) production-based industries, therefore, the discovery of chitosanases having commercial potential will remain a priority worldwide. This study aims to characterize different chitosanases of Bacillus strains for COS production. Six different indigenous Bacillus strains (B. cereus EGE-B-6.1m, B. cereus EGE-B-2.5m, B. cereus EGE-B-5.5m, B. cereus EGE-B-10.4i, B. thuringiensis EGE-B-3.5m, and B. mojavensis EGE-B-5.2i) were used to purify and characterize chitosanases. All purified chitosanases have a similar molecular weight (37 kDa) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, other characteristics such as optimum temperature and pH, kinetic parameters (K_m and V_max ), temperature, and pH stabilities were dissimilar among the strains of different Bacillus species and within the same species. Furthermore, chitosanases of all strains were able to successfully hydrolyze chitosan to COS and oligomers of the degree of polymerization 2-6 were detected with chitobiose and chitotriose as major hydrolysis products. The relative yields of COS were in a range of 19%-31% and chitosanase of B. thuringiensis EGE-B-3.5m turned out to be the best enzyme in terms of its characteristics and COS production potential with maximum relative yield (31%). Results revealed that Bacillus chitosanases could be used directly for efficient bioconversion of chitosan into COS and will be valuable for large-scale production of biologically active COS.

Gene cloning and molecular characterization of a thermostable chitosanase from Bacillus cereus TY24

Background

An important conceptual advance in health and the environment has been recognized that enzymes play a key role in the green processing industries. Of particular interest, chitosanase is beneficial for recycling the chitosan resource and producing chitosan oligosaccharides. Also, chitosan gene expression and molecular characterization will promote understanding of the biological function of bacterial chitosanase as well as explore chitosanase for utilizing chitosan resources.

Results

A chitosanase-producing bacterium TY24 was isolated and identified as Bacillus cereus. Moreover, the chitosanase gene was cloned and expressed in Escherichia coli. Sequence analysis reveals that the recombinant chitosanase (CHOE) belongs to the glycoside hydrolases 8 family. The purified CHOE has a molecular weight of about 48 kDa and the specific activity of 1150 U/mg. The optimal pH and temperature of CHOE were 5.5 and 65 °C, respectively. The enzyme was observed stable at the pH range of 4.5–7.5 and the temperature range of 30–65 °C. Especially, the half-life of CHOE at 65 °C was 161 min. Additionally, the activity of CHOE was remarkably enhanced in the presence of Mn²⁺, Cu²⁺, Mg²⁺ and K⁺, beside Ca²⁺ at 5 mM. Especially, the activity of CHOE was enhanced to more than 120% in the presence of 1% of various surfactants. CHOE exhibited the highest substrate specificity toward colloid chitosan.

Conclusion

A bacterial chitosanase was cloned from B. cereus and successfully expressed in E. coli (BL21) DE3. The recombinant enzyme displayed good stability under acid pH and high-temperature conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-022-00762-6.

Insights into promiscuous chitosanases: the known and the unknown

Chitosanase, a glycoside hydrolase (GH), catalyzes the cleavage of β-1,4-glycosidic bonds in polysaccharides and is widely distributed in nature. Many organisms produce chitosanases, and numerous chitosanases in the GH families have been intensely studied. The reported chitosanases mainly cleaved the inter-glucosamine glycosidic bonds, while substrate specificity is not strictly unique due to the existence of bifunctional or multifunctional activity profiles. The promiscuity of chitosanases is essential for the different pathways of biomass polysaccharide conversion and understanding of the chitosanase evolutionary process. However, the reviews for this aspect are completely unknown. This review provides an overview of the promiscuous activities, also considering the substrate and product specificity of chitosanases observed to date. These contribute to important implications for the future discovery and research of promiscuous chitosanases and applications related to biomass conversion. KEY POINTS: • The promiscuity of chitosanases is reviewed for the first time. • The current review provides insights into the substrate specificity of chitosanases. • The mode-product relationship and prospect of promiscuous chitosanases are highlighted.

Potential Medical Applications of Chitooligosaccharides

Chitooligosaccharides, also known as chitosan oligomers or chitooligomers, are made up of chitosan with a degree of polymerization (DP) that is less than 20 and an average molecular weight (MW) that is lower than 3.9 kDa. COS can be produced through enzymatic conversions using chitinases, physical and chemical applications, or a combination of these strategies. COS is of significant interest for pharmacological and medical applications due to its increased water solubility and non-toxicity, with a wide range of bioactivities, including antibacterial, anti-inflammatory, anti-obesity, neuroprotective, anticancer, and antioxidant effects. This review aims to outline the recent advances and potential applications of COS in various diseases and conditions based on the available literature, mainly from preclinical research. The prospects of further in vivo studies and translational research on COS in the medical field are highlighted.

Constitutive chitosanase from Bacillus thuringiensis B-387 and its potential for preparation of antimicrobial chitooligomers

The article proves the ability of the entomopathogenic strain B. thuringiensis var. dendrolimus B-387 to high the constitutive production (3-12.5 U/mL) of extracellular chitosanase, that was found for the first time. The enzyme was purified in 94-fold by ultrafiltration, affinity sorption and cation-exchange chromatography and characterized biochemically. The molecular mass of the chitosanase determined using SDS-PAGE is 40 kDa. Temperature and pH-optima of the enzyme are 55 ^°C and pH 6.5, respectively; the chitosanase was stable under 50-60 ^°C and pH 4-10.5. Purified chitosanase most rapidly (V_max ~ 43 µM/mL × min, K_M ~ 0.22 mg/mL, k_cat ~ 4.79 × 10⁴ s^-1) hydrolyzed soluble chitosan of the deacetylation degree (DD) 85% by endo-mode, and did not degrade colloidal chitin, CM-cellulose and some other glucans. The main reaction products of the chitosan enzymolysis included chitobiose, chitotriose and chitotetraose. In addition to small chitooligosaccharides (CHOs), the studied chitosanase also generated low-molecular weight chitosan (LMWC) with average M_w in range 14-46 kDa and recovery 14-35%, depending on the enzyme/substrate ratio and incubation temperature. In some cases, the chitosan (DD 85 and 50%) oligomers prepared using crude chitosanase from B. thuringiensis B-387 indicated higher antifungal and antibacterial activities in vitro in comparison with the initial polysaccharides. The data obtained indicate the good prospect of chitosanase B-387 for the production of bioactive CHOs.

Low molecular weight chitooligosaccharide inhibits infection of SARS-CoV-2 in vitro

AIMS

The discovery of antiviral substances to respond to COVID-19 is a global issue, including the field of drug development based on natural materials. Here, we showed that chitosan-based substances have natural antiviral properties against SARS-CoV-2 in vitro.

METHODS AND RESULTS

The molecular weight of chitosan-based substances was measured by the gel permeation chromatography analysis. In MTT assay, the chitosan-based substances have low cytotoxicity to Vero cells. The antiviral effect of these substances was confirmed by quantitative viral RNA targeting the RdRp and E genes and plaque assay. Among the substances tested, low molecular weight chitooligosaccharide decreased the fluorescence intensity of SARS-CoV-2 nucleocapsid protein of the virus-infected cells in a dose-dependent manner.

CONCLUSIONS

In conclusion, the chitooligosaccharide, a candidate for natural treatment, has antiviral effects against the SARS-CoV-2 virus in vitro.

SIGNIFICANCE AND IMPACT OF STUDY

In this study, it was suggested for the first time that chitosan-based substances such as chitooligosaccharide can have an antiviral effect on SARS-CoV-2 in vitro.

A Novel Chitosanase from Penicillium oxalicum M2 for Chitooligosaccharide Production: Purification, Identification and Characterization

This study discovered a novel chitosanase from Penicillium oxalicum M2 based on a new screening strategy. An extracellular chitosanase was isolated and purified from the fermentation broth of Penicillium oxalicum M2. A 19.34-fold purification was achieved on a cation exchange column. Using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, chitosanase was determined at approximately 42 kDa without any subunits. The sequence of peptide in the protein was identified as SALNKNYITNFSTLR by MALTI-TOF/TOF MS. The maximum catalytic activity of the purified enzyme was 60.45 U/mg at the optimum pH and temperature of 5.5 and 60 °C. The enzyme activity held stability in the range of 35-50 °C and pH 3-4.5. Ca²⁺, Mn²⁺, non-ionic surfactants (Tween 20/40/60/80 and Trition X-100) and some common reducing agents (DTT and β-ME) could significantly activate chitosanase. The purified enzyme showed rigorous specificity to chitosan as a substrate. The hydrolysate in the final stage of hydrolysis consisted of chitooligosaccharides with a degree of polymerization ranging from 2 to 5 and without glucosamine or acetylglucosamine. The monomeric enzyme obtained by one-step purification reveal applications potential in sugar industry, and expanded our understanding of the GH75 family chitosanases simultaneously.

Immobilized fungal enzymes: Innovations and potential applications in biodegradation and biosynthesis

Microbial enzymes catalyze various reactions inside and outside living cells. Among the widely studied enzymes, fungal enzymes have been used for some of the most diverse purposes, especially in bioremediation, biosynthesis, and many nature-inspired commercial applications. To improve their stability and catalytic ability, fungal enzymes are often immobilized on assorted materials, conventional as well as nanoscale. Recent advances in fungal enzyme immobilization provide effective and sustainable approaches to achieve improved environmental and commercial outcomes. This review aims to provide a comprehensive overview of commonly studied fungal enzymes and immobilization technologies. It also summarizes recent advances involving immobilized fungal enzymes for the degradation or assembly of compounds used in the manufacture of products, such as detergents, food additives, and fossil fuel alternatives. Furthermore, challenges and future directions are highlighted to offer new perspectives on improving existing technologies and addressing unexplored fields of applications.

Biochemical characterization and cleavage pattern analysis of a novel chitosanase with cellulase activity

Chitosanases are critical tools for the preparation of active oligosaccharides, whose composition is related to the cleavage pattern of the enzyme. Although numerous chitosanases have been characterized, the glycoside hydrolase (GH) family 5 chitosanases with other activities have rarely been investigated. Herein, a novel and second GH5 chitosanase OUC-Csngly from Streptomyces bacillaris was cloned and further characterized by expression in Escherichia coli BL21 (DE3). Interestingly, OUC-Csngly possessed dual chitosanase and cellulase activities. Molecular docking analysis showed that the C-2 group of sugar units affected the binding of the enzyme to oligosaccharides, which could result in different cleavage patterns toward chito-oligosaccharides (COSs) and cello-oligosaccharides. Further, we characterized OUC-Csngly's distinctive cleavage patterns toward two different types of oligosaccharides. Meanwhile, endo-type chitosanase OUC-Csngly generated (GlcN) - (GlcN)₄ from chitosan, was significantly different from other chitosanases. To our knowledge, this is the first report to investigate the different cleavage patterns of chitosanase for COSs and cello-oligosaccharides.Key points• The molecular docking showed C-2 group of sugar units in substrate affecting the cleavage pattern.• The first chitosanase exhibited different cleavage patterns towards chito- and cello-oligosaccharides.• The groups at C-2 influence the subsite composition of the enzyme's active cleft.

Chitooligosaccharides production from shrimp chaff in chitosanase cell surface display system

Chitin refers to a natural biopolymer, which is economically significant to next-generation biorefineries. In this study, a novel high-yield method with cell surface-display chitosanase (CHI-1) was built to produce chitooligosaccharides (COS) from shrimp chaff through the co-fermentation in the presence of Bacillus subtilis and Acetobacter sp. Under the optimized co-fermentation conditions (5 g/L yeast extracts, 10 g/L KH₂PO₄, 6% ethanol, 50 g/L glucose), the final deproteinization (DP) and demineralization (DM) efficiency and the chitin yield were achieved as 94, 92 and 18%, respectively. The engineered E. coli BL21-pET23b(+)-NICHI maintained 81% of the initial enzyme activity after 40 days at room temperature. The crude CHI-1 was inactivated after one-day interacting with prepared chitosan. Moreover, E. coli BL21-pET23b(+)-NICHI still maintained excellent hydrolysis ability in 7 days, and the COS yield reached 41%. Accordingly, the proposed method exhibited excellent stability and a high hydrolysis efficiency to produce COS with whole engineered cells.

Expression and Surface Display of an Acidic Cold-Active Chitosanase in Pichia pastoris Using Multi-Copy Expression and High-Density Cultivation

Chitosanase hydrolyzes β-(1,4)-linked glycosidic bonds are used in chitosan chains to release oligosaccharide mixtures. Here, we cloned and expressed a cold-adapted chitosanase (CDA, Genbank: MW094131) using multi-copy expression plasmids (CDA1/2/3/4) in Pichia pastoris. We identified elevated CDA expression levels in multi-copy strains, with strain PCDA4 selected for high-density fermentation and enzyme-activity studies. The high-density fermentation approach generated a CDA yield of 20014.8 U/mL, with temperature and pH optimization experiments revealing the highest CDA activity at 20 °C and 5.0, respectively. CDA was stable at 10 °C and 20 °C. Thus, CDA could be used at low temperatures. CDA was then displayed on P. pastoris using multi-copy expression plasmids. Then, multi-copy strains were constructed and labelled as PCDA(1-3)-AGα1. Further studies showed that the expression of CDA(1-3)-AGα1 in multi-copy strains was increased, and that strain PCDA3-AGα1 was chosen for high-density fermentation and enzyme activity studies. By using a multi-copy expression and high-density fermentation approach, we observed CDA-AGα1 expression yields of 102415 U/g dry cell weight. These data showed that the displayed CDA exhibited improved thermostability and was more stable over wider temperature and pH ranges than free CDA. In addition, displayed CDA could be reused. Thus, the data showed that displaying enzymes on P. pastoris may have applications in industrial settings.

Biochemical characterization of a novel bifunctional chitosanase from Paenibacillus barengoltzii for chitooligosaccharide production

A novel chitosanase gene, designated as PbCsn8, was cloned from Paenibacillus barengoltzii. It shared the highest identity of 73% with the glycoside hydrolase (GH) family 8 chitosanase from Bacillus thuringiensis JAM-GG01. The gene was heterologously expressed in Bacillus subtilis as an extracellular protein, and the highest chitosanase yield of 1, 108 U/mL was obtained by high-cell density fermentation in a 5-L fermentor. The recombinant chitosanase (PbCsn8) was purified to homogeneity and biochemically characterized. PbCsn8 was most active at pH 5.5 and 70 °C, respectively. It was stable in a wide pH range of 5.0-11.0 and up to 55 °C. PbCsn8 was a bifunctional enzyme, exhibiting both chitosanase and glucanase activities, with the highest specificity towards chitosan (360 U/mg), followed by barley β-glucan (72 U/mg) and lichenan (13 U/mg). It hydrolyzed chitosan to release mainly chitooligosaccharides (COSs) with degree of polymerization (DP) 2-3, while hydrolyzed barley β-glucan to yield mainly glucooligosaccharides with DP > 5. PbCsn8 was further applied in COS production, and the highest COS yield of 79.3% (w/w) was obtained. This is the first report on a GH family 8 chitosanase from P. barengoltzii. The high yield and remarkable hydrolysis properties may make PbCsn8 a good candidate in industrial application.

Cloning and Characterization of a New Chitosanase From a Deep-Sea Bacterium Serratia sp. QD07

Chitosanase is a significant chitosan-degrading enzyme involved in industrial applications, which forms chitooligosaccharides (COS) as reaction products that are known to have various biological activities. In this study, the gene csnS was cloned from a deep-sea bacterium Serratia sp. QD07, as well as over-expressed in Escherichia coli, which is a new chitosanase encoding gene. The recombinant strain was cultured in a 5 L fermenter, which yielded 324 U/mL chitosanases. After purification, CsnS is a cold-adapted enzyme with the highest activity at 60°C, showing 37.5% of the maximal activity at 0°C and 42.6% of the maximal activity at 10°C. It exhibited optimum activity at pH 5.8 and was stable at a pH range of 3.4–8.8. Additionally, CsnS exhibited an endo-type cleavage pattern and hydrolyzed chitosan polymers to yield disaccharides and trisaccharides as the primary reaction products. These results make CsnS a potential candidate for the industrial manufacture of COS.

Marine-polysaccharide degrading enzymes: Status and prospects

Marine-polysaccharide degrading enzymes have recently been studied extensively. They are particularly interesting as they catalyze the cleavage of glycosidic bonds in polysaccharide macromolecules and produce oligosaccharides with low degrees of polymerization. Numerous findings have demonstrated that marine polysaccharides and their biotransformed products possess beneficial properties including antitumor, antiviral, anticoagulant, and anti-inflammatory activities, and they have great value in healthcare, cosmetics, the food industry, and agriculture. Exploitation of enzymes that can degrade marine polysaccharides is in the ascendant, and is important for high-value use of marine biomass resources. In this review, we describe research and prospects regarding the classification, biochemical properties, and catalytic mechanisms of the main types of marine-polysaccharide degrading enzymes, focusing on chitinase, chitosanase, alginate lyase, agarase, and carrageenase, and their product oligosaccharides. The state-of-the-art discussion of marine-polysaccharide degrading enzymes and their properties offers information that might enable more efficient production of marine oligosaccharides. We also highlight current problems in the field of marine-polysaccharide degrading enzymes and trends in their development. Understanding the properties, catalytic mechanisms, and modification of known enzymes will aid the identification of novel enzymes to degrade marine polysaccharides and facilitation of their use in various biotechnological processes.

The Significance of Bacillus spp. in Disease Suppression and Growth Promotion of Field and Vegetable Crops

Bacillus spp. produce a variety of compounds involved in the biocontrol of plant pathogens and promotion of plant growth, which makes them potential candidates for most agricultural and biotechnological applications. Bacilli exhibit antagonistic activity by excreting extracellular metabolites such as antibiotics, cell wall hydrolases, and siderophores. Additionally, Bacillus spp. improve plant response to pathogen attack by triggering induced systemic resistance (ISR). Besides being the most promising biocontrol agents, Bacillus spp. promote plant growth via nitrogen fixation, phosphate solubilization, and phytohormone production. Antagonistic and plant growth-promoting strains of Bacillus spp. might be useful in formulating new preparations. Numerous studies of a wide range of plant species revealed a steady increase in the number of Bacillus spp. identified as potential biocontrol agents and plant growth promoters. Among different mechanisms of action, it remains unclear which individual or combined traits could be used as predictors in the selection of the best strains for crop productivity improvement. Due to numerous factors that influence the successful application of Bacillus spp., it is necessary to understand how different strains function in biological control and plant growth promotion, and distinctly define the factors that contribute to their more efficient use in the field.

Bioprocess development for L-asparaginase production by Streptomyces rochei, purification and in-vitro efficacy against various human carcinoma cell lines

In the near future, the demand for L-asparaginase is expected to rise several times due to an increase in its clinical and industrial applications in various industrial sectors, such as food processing. Streptomyces sp. strain NEAE-K is potent L-asparaginase producer, isolated and identified as new subsp. Streptomyces rochei subsp. chromatogenes NEAE-K and the sequence data has been deposited under accession number KJ200343 at the GenBank database. Sixteen different independent factors were examined for their effects on L-asparaginase production by Streptomyces rochei subsp. chromatogenes NEAE-K under solid state fermentation conditions using Plackett-Burman design. pH, dextrose and yeast extract were the most significant factors affecting L-asparaginase production. Thus, using central composite design, the optimum levels of these variables were determined. L-asparaginase purification was carried out by ammonium sulfate followed by DEAE-Sepharose CL-6B ion exchange column with a final purification fold of 16.18. The monomeric molecular weight of the purified L-asparaginase was 64 kD as determined by SDS-PAGE method. The in vitro effects of L-asparaginase were evaluated on five human tumor cell lines and found to have a strong anti-proliferative effects. The results showed that the strongest cytotoxic effect of L-asparaginase was exerted on the HeLa and HepG-2 cell lines (IC50 = 2.16 ± 0.2 and 2.54 ± 0.3 U/mL; respectively). In addition, the selectivity index of L-asparaginase against HeLa and HepG-2 cell lines was 3.94 and 3.35; respectively.

Identification of cholesterol-assimilating actinomycetes strain and application of statistical modeling approaches for improvement of cholesterol oxidase production by Streptomyces anulatus strain NEAE-94

Background

Cholesterol oxidase biosensors have been used to determine the level of cholesterol in different serum and food samples. Due to a wide range of industrial and clinical applications of microbial cholesterol oxidase, isolation and identification of a new microbial source (s) of cholesterol oxidase are very important.

Results

The local isolate Streptomyces sp. strain NEAE-94 is a promising source of cholesterol oxidase. It was identified based on cultural, morphological and physiological characteristics; in addition to the 16S rRNA sequence. The sequencing product had been deposited in the GenBank database under the accession number KC354803. Cholesterol oxidase production by Streptomyces anulatus strain NEAE-94 in shake flasks was optimized using surface response methodology. The different process parameters were first screened using a Plackett-Burman design and the parameters with significant effects on the production of cholesterol oxidase were identified. Out of the 15 factors screened, agitation speed, cholesterol and yeast extract concentrations had the most significant positive effects on the production of cholesterol oxidase. The optimal levels of these variables and the effects of their mutual interactions on cholesterol oxidase production were determined using Box-Behnken design. Cholesterol oxidase production by Streptomyces anulatus strain NEAE-94 was 11.03, 27.31 U/mL after Plackett-Burman Design and Box-Behnken design; respectively, with a fold of increase of 6.06 times compared to the production before applying the Plackett-Burman design (4.51 U/mL).

Conclusions

Maximum cholesterol oxidase activity was obtained at the following fermentation conditions: g/L (cholesterol 4, yeast extract 5, NaCl 0.5, K₂HPO₄ 1, FeSO₄.7H₂O 0.01, MgSO₄.7H₂O 0.5), pH 7, inoculum size 4% (v/v), temperature 37°C, agitation speed of 150 rpm, medium volume 50 mL and incubation time 5 days.

Cloning and Characterization of a Cold-adapted Chitosanase from Marine Bacterium Bacillus sp. BY01

Chitosanase plays an important role in the production of chitooligosaccharides (CHOS), which possess various biological activities. Herein, a glycoside hydrolase (GH) family 46 chitosanase-encoding gene, csnB, was cloned from marine bacterium Bacillus sp. BY01 and heterologously expressed in Escherichia coli. The recombinant chitosanase, CsnB, was optimally active at 35 °C and pH 5.0. It was also revealed to be a cold-adapted enzyme, maintaining 39.5% and 40.4% of its maximum activity at 0 and 10 °C, respectively. Meanwhile, CsnB showed wide pH-stability within the range of pH 3.0 to 7.0. Then, an improved reaction condition was built to enhance its thermostability with a final glycerol volume concentration of 20%. Moreover, CsnB was determined to be an endo-type chitosanase, yielding chitosan disaccharides and trisaccharides as the main products. Overall, CsnB provides a new choice for enzymatic CHOS production.

Expression of a Beauveria bassiana chitosanase (BbCSN-1) in Pichia pastoris and enzymatic analysis of the recombinant protein

Chitosanase (EC 3.2.1.132) is an important chitosan-degrading enzyme involved in industrial applications. In this study, a chitosanase gene (BbCSN-1) from Beauveria bassiana, an insect fungal pathogen, was cloned and expressed in Pichia pastoris. The amount of BbCSN-1 in the fermentation broth of P. pastoris gradually increased after induction with methanol from one to 6 d, reaching 398 μg/ml on the 6th day. The molecular characteristics of BbCSN-1 were measured with colloidal chitosan as a substrate. The purified BbCSN-1 exhibited optimum activity at pH 5 and 30 °C and was stable at pH 2-8 and below 40 °C. The Km value of BbCSN-1 was approximately 0.8 mg/ml at 30 °C (pH 6.0). The activity of BbCSN-1 was significantly enhanced by Mn²⁺ but inhibited by Co²⁺ and Cu²⁺. These results indicated that BbCSN-1 from B. bassiana could be easily expressed in P. pastoris, which provided a basis for further study on its application.

Characterization and antifungal activity of chitosanase produced by Pedobacter sp. PR-M6

To investigate the temperature requirements of chitosanase activity, as well as the degradation patterns generated by enzyme-induced chitosan oligomer hydrolysis, Pedobacter sp. PR-M6 was inoculated onto 0.5% colloidal chitosan medium agar plates. Cell growth was higher at 30 °C than at 20 °C during the initial 2 days of incubation. The protein content rapidly increased on day 1 at both temperatures and then it slowly increased at 20 °C and slowly decreased at 30 °C during the following 5 days of incubation. In order to characterize the electrophoretic pattern, Pedobacter sp. PR-M6 was cultured in 1% powder chitosan medium at 20 °C and 30 °C for 5 days after incubation and analyzed by SDS-PAGE. Four bands were visible, corresponding to ct1 (25 kDa), ct2 (17 kDa), ct3 (15 kDa), and ct4 (14 kDa), at both 20 °C and 30 °C. The optimal conditions for the activity of chitosanase produced from Pedobacter sp. PR-M6 were 60 °C and 1.81 enzyme units/mg protein. Two major isozyme bands (ct3 and ct4) exhibited their strongest chitosanase activity at 50 °C in SDS-PAGE gel. The reaction products generated from (GlcN)₂-(GlcN)₅ substrates at 60 °C after a 1 h incubation were investigated by thin-layer chromatography. Low-molecular weight chitosan and oligochitosan (LCOC) and soluble chitosan showed antifungal activity against A. brassicicola, B. cinerea, F. solani, and R. solani. LCOC exhibited higher antifungal activity than soluble chitosan. Moreover, LCOC treatments (500 ppm and 1000 ppm) inhibited conidia germination in A. brassicicola.

Cloning, expression and characterization of a novel chitosanase from Streptomyces albolongus ATCC 27414

A gene encoding chitosanase from Streptomyces albolongus was cloned, sequenced and expressed in Escherichia coli. The novel recombinant enzyme (Csn21c) was purified by Ni-NTA Superflow Column and showed a molecular mass of 29.6 kDa by SDS-PAGE. The enzyme Csn21c showed the optimal activity in 50 mmol/L Tris-HCl buffer, pH 8.0, and 50 °C and it was strongly activated (2-fold) by Mn²⁺. It belonged to glycoside hydrolase 46 family according to NCBI database (http://www.ncbi.nlm.nih.gov/) and displayed an exo-type cleavage pattern, hydrolyzing chitosan mainly into d-glucosamine (GlcN) and chitobiose ((GlcN)₂) as confirmed by TLC and MS analysis. This study demonstrated that Csn21c can be an effective tool to produce abundant glucosamine and chitooligosaccharides (COS) from chitosan.

Structural and biochemical insight into mode of action and subsite specificity of a chitosan degrading enzyme from Bacillus spec. MN

Chitosans, partially de-N-acetylated derivatives of chitin, are multifunctional biopolymers. In nature, biological activities of partially acetylated chitosan polymers are mediated in part by their oligomeric breakdown products, which are generated in situ by the action of chitosanolytic enzymes. Understanding chitosanolytic enzymes, therefore, can lead to the production of chitosan oligomers with fully defined structures that may confer specific bioactivities. To address whether defined oligomer products can be produced via chitosanolytic enzymes, we here characterized a GH8 family chitosanase from Bacillus spec. MN, determining its mode of action and product profiles. We found that the enzyme has higher activity towards polymers with lower degree of acetylation. Oligomeric products were dominated by GlcN₃, GlcN₃GlcNAc₁, and GlcN₄GlcNAc₁. The product distribution from oligomers were GlcN₃ > GlcN₂. Modeling and simulations show that the binding site comprises subsites ranging from (-3) to (+3), and a putative (+4) subsite, with defined preferences for GlcN or GlcNAc at each subsite. Flexible loops at the binding site facilitate enzyme-substrate interactions and form a cleft at the active site which can open and close. The detailed insight gained here will help to engineer enzyme variants to produce tailored chitosan oligomers with defined structures that can then be used to probe their specific biological activities.

Examining the interplay between Streptococcus agalactiae, the biopolymer chitin and its derivative

Streptococcus agalactiae is a highly pathogenic bacterium of aquatic species and terrestrial animals worldwide, whereas chitin and its derivative chitosan are among the most abundant biopolymers found in nature, including the aquatic milieu. The present investigation focused on the capability of S. agalactiae to degrade and utilize these polymers. Growth of S. agalactiae in the presence of colloid chitin, chitosan, or N‐acetyl‐glucosamine (GlcNAc) was evaluated. Chitosanase production was measured daily over 7 days of growth period and degraded products were evaluated with thin later chorography. Chitin had no effect on the growth of S. agalactiae. Degraded chitin, however, stimulated the growth of S. agalactiae. S. agalactiae cells did not produce chitinase to degrade chitin; however, they readily utilize GlcNAc (product of degraded chitin) as sole source of carbon and nitrogen for growth. Chitosan at high concentrations had antibacterial activities against S. agalactiae, while in the presence of lower than the inhibitory level of chitosan in the medium, S. agalactiae secrets chitosanase to degrade chitosan, and utilizes it to a limited extent to benefit growth. The interaction of S. agalactiae with chitin hydrolytes and chitosan could play a role in the diverse habitat distribution and pathogenicity of S. agalactiae worldwide.

Immobilization of Chitosanases onto Magnetic Nanoparticles to Enhance Enzyme Performance

In this study, chitosanase cloning from Streptomyces albolongus was fermented and purified by a Ni-NTA column. Fe3O4-SiO2 magnetite nanoparticles (MNPs) were synthesized by the co-precipitation method coating with silica via a sol-gel reaction and were then amino functioned by treating with 3-aminopropyltriethoxysilane. Chitosanases were immobilized onto the surface of MNPs by covalent bonding (MNPs@chitosanase). Transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT–IR), and magnetic measurements were used to illustrate the MNPs and immobilized chitosanase. The optimal conditions of immobilization were studied. The thermal, pH, and stabilities of immobilized chitosanase were tested and the results showed that the stabilities were significantly enhanced compared with free chitosanase. After being recycled 10 times, the residual activity of the immobilized chitosanase was 43.7% of the initial activity.

Optimization of chitosanase production by Bacillus mojavensis EGE-B-5.2i

Maximum production of industrially important enzymes such as chitosanases through media optimization still holds foremost interest. The present study was conducted to improve chitosanase activity of an indigenous strain identified as Bacillus mojavensis. Initially, carbon and nitrogen sources were optimized by one-variable-at-a-time approach. Further, fermentation medium was optimized using Plackett-Burman (PB) and central composite designs (CCD). PB verified soluble starch (SS), colloidal chitosan (CC) peptone, and NaCl as most significant variables affecting chitosanase production. CCD results predicted the optimum concentrations of SS, CC, peptone, and NaCl as 7.8, 7.0, 6.5, and 2.7 g L^-1 , respectively to achieve maximum chitosanase activity (21.1 U ml^-1 ). Discovery of the novel optimal medium has improved chitosanase production by B. mojavensis up-to 9.5 folds. Lastly, 18.6 U ml^-1 chitosanase activity was achieved in stirred tank bioreactor using optimal medium, which is quite satisfactory to proclaim this strain as a potential candidate to provide commercial chitosanase.

Isolation and Evaluation of New Antagonist Bacillus Strains for the Control of Pathogenic and Mycotoxigenic Fungi of Fig Orchards

Bacillus is an antagonistic bacteria that shows high effectiveness against different phytopathogenic fungi and produces various lytic enzymes, such as chitosanase, chitinase, protease, and gluconase. The aim of this study is to determine Bacillus spp. for lytic enzyme production and to evaluate the antifungal effects of the selected strains for biocontrol of mycotoxigenic and phytopathogenic fungi. A total of 92 endospore-forming bacterial isolates from the 24 fig orchard soil samples were screened for chitosanase production, and six best chitosanolytic isolates were selected to determine chitinase, protease, and N-acetyl-β-hexosaminidase activity and molecularly identified. The antagonistic activities of six Bacillus strains against Aspergillus niger EGE-K-213, Aspergillus foetidus EGE-K-211, Aspergillus ochraceus EGE-K-217, and Fusarium solani KCTC 6328 were evaluated. Fungal spore germination inhibition and biomass inhibition activities were also measured against A. niger EGE-K-213. The results demonstrated that Bacillus mojavensis EGE-B-5.2i and Bacillus thuringiensis EGE-B-14.1i were more efficient antifungal agents against A. niger EGE-K-213. B. mojavensis EGE-B-5.2i has shown maximum inhibition of the biomass (30.4%), and B. thuringiensis EGE-B-14.1i has shown maximum inhibition of spore germination (33.1%) at 12 h. This is the first study reporting the potential of antagonist Bacillus strains as biocontrol agents against mycotoxigenic fungi of fig orchads.

Conversion of Squid Pens to Chitosanases and Proteases via Paenibacillus sp. TKU042

Chitosanases and proteases have received much attention due to their wide range of applications. Four kinds of chitinous materials, squid pens, shrimp heads, demineralized shrimp shells and demineralized crab shells, were used as the sole carbon and nitrogen (C/N) source to produce chitosanases, proteases and α-glucosidase inhibitors (αGI) by four different strains of Paenibacillus. Chitosanase productivity was highest in the culture supernatants using squid pens as the sole C/N source. The maximum chitosanase activity of fermented squid pens (0.759 U/mL) was compared to that of fermented shrimp heads (0.397 U/mL), demineralized shrimp shells (0.201 U/mL) and demineralized crab shells (0.216 U/mL). A squid pen concentration of 0.5% was suitable for chitosanase, protease and αGI production via Paenibacillus sp. TKU042. Multi-purification, including ethanol precipitation and column chromatography of Macro-Prep High S as well as Macro-Prep DEAE (diethylaminoethyl), led to the isolation of Paenibacillus sp. TKU042 chitosanase and protease with molecular weights of 70 and 35 kDa, respectively. For comparison, 16 chitinolytic bacteria, including strains of Paenibacillus, were investigated for the production of chitinase, exochitinase, chitosanase, protease and αGI using two kinds of chitinous sources.

Production of chitinase from Escherichia fergusonii, chitosanase from Chryseobacterium indologenes, Comamonas koreensis and its application in N-acetylglucosamine production

The important platform polysaccharide N-acetylglucosamine (GlcNAc) has great potential to be used in the fields of food, cosmetics, agricultural, pharmaceutical, medicine and biotechnology. This GlcNAc is being produced by traditional methods of environment-unfriendly chemical digestion with strong acids. Therefore, researchers have been paying more attention to enzymatic hydrolysis process for the production of GlcNAc. Hence, in this study, we isolated novel chitinase (Escherichia fergusonii) and chitosanase (Chryseobacterium indologenes, Comamonas koreensis) producing strains from Korean native calves feces, and developed the potential of an eco-friendly microbial progression for GlcNAc production from swollen chitin and chitosan by enzymatic degradation. Maximum chitinase (7.24±0.07U/ml) and chitosanase (8.42±0.09, 8.51±0.25U/ml) enzyme activity were reached in submerged fermentation at an optimal pH of 7.0 and 30°C. In this study, sucrose, yeast extract, (NH₄)₂SO₄, and NaCl were found to be the potential enhancers of exo-chitinase activity and glucose, corn flour, yeast extract, soybean flour, (NH₄)₂SO₄, NH₄Cl and K₂HPO₄ were found to be the potential activator for exo-chitosanase activity. Optimum concentrations of the carbon sources for enhanced chitinase activity were 9.91, 3.21, 9.86, 1.66U/ml and chitosanase activity were 1.63, 1.13, 2.28, 3.71, 9.02, 4.93, and 2.14U/ml. These enzymes efficiently hydrolyzed swollen chitin and chitosan to N-acetylglucosamine were characterized by thin layer chromatography and were further confirmed by high-pressure liquid chromatography. From a commercial perspective, we isolated, optimized and characterized exochitinase from Escherichia fergusonii (HANDI 110) and chitosanase from Chryseobacterium indologenes (HANYOO), and Comamonas koreensis (HANWOO) for the large-scale production of GlcNAc facilitating its potential use in industrial applications.