Purification, characterization, and gene cloning of a chitosanase from Bacillus species strain s65

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.

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.

Gene Cloning, Functional Expression, and Characterization of a Novel GH46 Chitosanase from Streptomyces avermitilis (SaCsn46A)

A n ovel glycoside hydrolase (GH) family 46 chitosanase (SaCsn46A) from Streptomyces avermitilis was cloned and functionally expressed in Escherichia coli Rosetta (DE3) strains. SaCsn46A consists of 271 amino acids, which includes a 34-amino acid signal peptide. The protein sequence of SaCsn46A shows maximum identity (83.5%) to chitosanase from Streptomyces sp. SirexAA-E. Then, the mature enzyme was purified to homogeneity through Ni-chelating affinity chromatography with a recovery yield of 78% and the molecular mass of purified enzyme was estimated to be 29 kDa by SDS-PAGE. The recombinant enzyme possessed a temperature optimum of 45 °C and a pH optimum of 6.2, and it was stable at pH ranging from 4.0 to 9.0 and below 30 °C. The Km and Vmax values of this enzyme were 1.32 mg/mL, 526.32 U/mg/min, respectively (chitosan as substrate). The enzyme activity can be enhanced by Mg2+ and especially Mn2+, which could enhance the activity about 3.62-fold at a 3-mM concentration. The enzyme can hydrolyze a variety of polysaccharides which are linked by β-1,4-glycosidic bonds such as chitin, xylan, and cellulose, but it could not hydrolyze polysaccharides linked by α-1,4-glycosidic bonds. The results of thin-layer chromatography and HPLC showed that the enzyme exhibited an endo-type cleavage pattern and could hydrolyze chitosan to glucosamine (GlcN) and (GlcN)2. This study demonstrated that SaCsn46A is a promising enzyme to produce glucosamine and chitooligosaccharides (COS) from chitosan.

Unraveling aerobic cultivable cellulolytic microorganisms within the gastrointestinal tract of sheep (Ovis aries) and their evaluation for cellulose biodegradation

Anaerobic cellulolytic microbes in gastrointestinal tract (GT) of ruminants have been well-documented, however, knowledge of aerobic microbes with cellulolytic activities in ruminant GT is comparably limited. Here, we unraveled aerobic cultivable cellulolytic microbes in GT of Ujimqin sheep (Ovis aries) and evaluated the cellulolytic potential of promising isolates. Twenty-two strains were found to possess cellulose degrading potential by Congo-red staining and phylogenetic analysis of the 16S rDNA/ITS sequence revealed that all strains belonged to nine genera, i.e., Bacillus, Streptomyces, Pseudomonas, Lactobacillus, Brachybacterium, Sanguibacter, Rhizobium, Fusarium, and Aspergillus. Strains with high cellulolytic activities were selected to further evaluate the various enzyme activities on lignocellulosic alfalfa hay (Medicago sativa). Among them, isolate Bacillus subtilis RE2510 showed the highest potential of cellulose degradation considering the high endoglucanase (0.1478 ± 0.0014 IU ml-1), exoglucanase (0.1735 ± 0.0012 IU ml-1) and β-glucosidase (0.3817 ± 0.0031 IU ml-1) after 10-day incubation with alfalfa hay. A significant destruction effect of the cellulose structure and the attachment of B. subtilis RE2510 to the hay were also revealed by using scanning electron microscope. This study expands our knowledge of aerobic cellulolytic isolates from GT of sheep and also highlights their potential application as microbial additive in the aerobic process of cellulose bioconversion.

An Antifungal Chitosanase from Bacillus subtilis SH21

Bacillus subtilis SH21 was observed to produce an antifungal protein that inhibited the growth of F. solani. To purify this protein, ammonium sulfate precipitation, gel filtration chromatography, and ion-exchange chromatography were used. The purity of the purified product was 91.33% according to high-performance liquid chromatography results. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis revealed that the molecular weight of the protein is 30.72 kDa. The results of the LC–MS/MS analysis and a subsequent sequence-database search indicated that this protein was a chitosanase, and thus, we named it chitosanase SH21. Scanning and transmission electron microscopy revealed that chitosanase SH21 appeared to inhibit the growth of F. solani by causing hyphal ablation, distortion, or abnormalities, and cell-wall depression. The minimum inhibitory concentration of chitosanase SH21 against F. solani was 68 µg/mL. Subsequently, the corresponding gene was cloned and sequenced, and sequence analysis indicated an open reading frame of 831 bp. The predicted secondary structure indicated that chitosanase SH21 has a typical a-helix from the glycoside hydrolase (GH) 46 family. The tertiary structure shared 40% similarity with that of Streptomyces sp. N174. This study provides a theoretical basis for a topical cream against fungal infections in agriculture and a selection marker on fungi.

Bioprospecting of a novel endophytic Bacillus velezensis FZ06 from leaves of Camellia assamica: Production of three groups of lipopeptides and the inhibition against food spoilage microorganisms

Food contamination caused by microorganisms has become a threat to consumers' health. Exploring antagonistic endophytes from plants of food raw-material and applying bioactive metabolites to inhibit the contamination has been an alternative and safer solution. In this study, we isolated and screened potential antagonistic endophytes from fresh Camellia assamica leaves, which were widely used in tea beverage production. We focused on a strain that showed visible inhibitory activity to Gram-positive bacteria, Gram-negative bacteria, and fungi. It was identified as a member of Bacillus velezensis and named FZ06. The results of genome analysis showed the strain FZ06 had 167 single-copy specific genes, much higher than those of most related strains. Also, 11 potential gene clusters of antimicrobial metabolites were found. Three groups of lipopeptides (surfactin, iturin, and fengycin) were identified by UPLC-MS/MS in purified antimicrobial methanol fraction of strain FZ06. The results of minimum inhibitory concentration (MIC) test proved the lipopeptide extract showed significant inhibitory effect on food spoilage bacteria (MIC 512-2048 μg/mL) and toxigenic fungi (MIC 128-256 μg/mL). In conclusion, this study suggests that the endophytic B. velezensis FZ06 and its lipopeptide extract hold great potential applications in the inhibition of food spoilage bacteria and toxic fungi in food industry.

Purification and identification of a novel antifungal protein from Bacillus subtilis XB-1

This study aimed to characterize a powerful antifungal component from bacteria. Bacillus subtilis strain XB-1, which showed maximal inhibition of Monilinia fructicola, was isolated and identified, and an antifungal protein was obtained from it. Ammonium sulfate precipitation, ion exchange chromatography, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to purify and identify the proteins secreted by B. subtilis XB-1. Analyses revealed that purified fraction V had the strongest antifungal effect, with the largest pathogen inhibition zone diameter of 4.15 cm after 4 days (P < 0.05). This fraction showed a single band with a molecular weight of approximately 43 kDa in SDS-PAGE. Results from SDS-PAGE and liquid chromatography electrospray ionization tandem mass spectrometry analyses demonstrated that fraction V was likely a member of the chitosanase family. These results suggest that B. subtilis XB-1 and its antifungal protein may be useful in potential biocontrol applications.

Modification of Chitosan for the Generation of Functional Derivatives

Today, chitosan (CS) is probably considered as a biofunctional polysaccharide with the most notable growth and potential for applications in various fields. The progress in chitin chemistry and the need to replace additives and non-natural polymers with functional natural-based polymers have opened many new opportunities for CS and its derivatives. Thanks to the specific reactive groups of CS and easy chemical modifications, a wide range of physico-chemical and biological properties can be obtained from this ubiquitous polysaccharide that is composed of β-(1,4)-2-acetamido-2-deoxy-d-glucose repeating units. This review is presented to share insights into multiple native/modified CSs and chitooligosaccharides (COS) associated with their functional properties. An overview will be given on bioadhesive applications, antimicrobial activities, adsorption, and chelation in the wine industry, as well as developments in medical fields or biodegradability.

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.

Discovery and Characterization of a Novel Chitosanase from Paenibacillus dendritiformis by Phylogeny-Based Enzymatic Product Specificity Prediction

In the process of genome mining for novel chitosanases by phylogeny-based enzymatic product specificity prediction, a gene named Csn-PD from Paenibacillus dendritiformis was discovered. The enzyme was classified as a member of the GH46 family of glycoside hydrolase based on sequence alignment, and it was functionally expressed in Escherichia coli BL21 (DE3). The recombinant chitosanase was purified, and its molecular weight was estimated to be 31 kDa by SDS-PAGE. Csn-PD displayed maximal activity toward colloidal chitosan at pH 7.0 and 45 °C, respectively. A combination of thin-layer chromatography and electrospray ionization-mass spectrometry results showed that Csn-PD exhibited an endotype cleavage pattern and hydrolyzed chitosan to yield (GlcN)₂ as the major product. The unique enzymatic properties of this chitosanase may make it a good candidate for (GlcN)₂ production.

Expression and characterization of a novel cold-adapted chitosanase suitable for chitooligosaccharides controllable preparation

Chitooligosaccharide is widely used as a functional food additive and a valuable pharmacological agent. The transformation of chitinous biomass into valuable bioactive chitooligosaccharides is one of the most exciting applications of chitosanase. A novel glycoside hydrolase (GH) family 46 chitosanase (GsCsn46A) from rhizobacterium Gynuella sunshinyii was cloned and heterologously expressed in Escherichia coli. GsCsn46A showed maximal activity at pH 5.5 and 30 °C. GsCsn46A featured remarkable cold-adapted property, which controllably hydrolyzed chitosan to three types of chitooligosaccharides at the mild reaction condition (reaction condition: pH 5.5 at 30 °C; method for stopping the reaction: 50 °C for 30 min). The yields of three types of chitooligosaccharides products (degree of polymerization (DP): 2-7, 2-5 and 2-3) were 70.9%, 87.1% and 94.6% respectively. This novel cold-adapted chitosanase provides a cleaner production process for the controllable preparation of chitooligosaccharides with the specific DP.

Enzymatic production of glucosamine and chitooligosaccharides using newly isolated exo-β-D-glucosaminidase having transglycosylation activity

Exochitosanase secreting fungus (A. fumigatus IIT-004) was isolated from fish waste using 1 % (w/v) chitosan as sole carbon source after multistage screening. Chitosan-dependent exochitosanase enzyme production (6 IU ml⁻¹) in log phase of growth (chitosan utilization rate 0.11 g g⁻¹ cell h⁻¹) was observed for Aspergillus fumigatus in chitosan minimal salt medium and there was no enzyme production in glucose medium. Enzyme production was found to be extracellular and subjected to purification by a number of steps like acetone fractionation as well as column chromatography. 40 % yield and 26-fold of enzyme purification was achieved after all the steps. Purified enzyme was characterized for optimum temperature, pH, ionic strength and substrate specificity. The K_m and V_max for purified exochitosanase enzyme was calculated to be 8 mg ml⁻¹ and 5.2 × 10⁻⁶ mol mg⁻¹ min⁻¹. Enzyme was immobilized on polyacrylonitrile nanofibres membrane matrix by adsorption as well as amidination. Enzymatic production of glucosamine was achieved using various chitosan substrates by free/immobilized exochitosanase and compared. Isolated and purified exochitosanase also showed transglycosylation activity.

Recent Progress in Chitosanase Production of Monomer-Free Chitooligosaccharides: Bioprocess Strategies and Future Applications

Biological activities of chitosan oligosaccharides (COS) are well documented, and numerous reports of COS production using specific and non-specific enzymes are available. However, strategies for improving the overall yield by making it monomer free need to be developed. Continuous enzymatic production from chitosan derived from marine wastes is desirable and is cost-effective. Isolation of potential microbes showing chitosanase activity from various ecological niches, gene cloning, enzyme immobilization, and fractionation/purification of COS are some areas, where lot of work is in progress. This review covers recent measures to improve monomer-free COS production using chitosanase/non-specific enzymes and purification/fractionation of these molecules using ultrafiltration and column chromatographic techniques. Various bioprocess strategies, gene cloning for enhanced chitosanase enzyme production, and other measures for COS yield improvements have also been covered in this review. COS derivative preparation as well as COS-coated nanoparticles for efficient drug delivery are being focused in recent studies.

A High Diversity in Chitinolytic and Chitosanolytic Species and Enzymes and Their Oligomeric Products Exist in Soil with a History of Chitin and Chitosan Exposure

Chitin is one of the most abundant biomolecules on earth, and its partially de-N-acetylated counterpart, chitosan, is one of the most promising biotechnological resources due to its diversity in structure and function. Recently, chitin and chitosan modifying enzymes (CCMEs) have gained increasing interest as tools to engineer chitosans with specific functions and reliable performance in biotechnological and biomedical applications. In a search for novel CCME, we isolated chitinolytic and chitosanolytic microorganisms from soils with more than ten-years history of chitin and chitosan exposure and screened them for chitinase and chitosanase isoenzymes as well as for their patterns of oligomeric products by incubating their secretomes with chitosan polymers. Of the 60 bacterial strains isolated, only eight were chitinolytic and/or chitosanolytic, while 20 out of 25 fungal isolates were chitinolytic and/or chitosanolytic. The bacterial isolates produced rather similar patterns of chitinolytic and chitosanolytic enzymes, while the fungal isolates produced a much broader range of different isoenzymes. Furthermore, diverse mixtures of oligosaccharides were formed when chitosan polymers were incubated with the secretomes of select fungal species. Our study indicates that soils with a history of chitin and chitosan exposure are a good source of novel CCME for chitosan bioengineering.

Chitinolytic Bacteria-Assisted Conversion of Squid Pen and Its Effect on Dyes and Pigments Adsorption

The aim of this work was to produce chitosanase by fermenting from squid pen, and recover the fermented squid pen for dye removal by adsorption. One chitosanase induced from squid pen powder (SPP)-containing medium by Bacillus cereus TKU034 was purified in high purification fold (441) and high yield of activity recovery (51%) by ammonium sulfate precipitation and combined column chromatography. The SDS-PAGE results showed its molecular mass to be around 43 kDa. The TKU034 chitosanase used for the chitooligomers preparation was studied. The enzyme products revealed that the chitosanase could degrade chitosan with various degrees of polymerization, ranging from 3 to 9, as well as the chitosanase in an endolytic manner. Besides, the fermented SPP was recovered and displayed a better adsorption rate (up to 99.5%) for the disperse dyes (red, yellow, blue, and black) than the water-soluble food colorants, Allura Red AC (R40) and Tartrazine (Y4). The adsorbed R40 on the unfermented SPP and the fermented SPP was eluted by distilled water and 1 M NaOH to confirm the dye adsorption mechanism. The fermented SPP had a slightly higher adsorption capacity than the unfermented, and elution of the dye from the fermented SPP was easier than from the unfermented. The main dye adsorption mechanism of fermented SPP was physical adsorption, while the adsorption mechanism of unfermented SPP was chemical adsorption.

Extracellular overexpression of chitosanase from Bacillus sp. TS in Escherichia coli

The chitosanase gene from a Bacillus sp. strain isolated from soil in East China was cloned and expressed in Escherichia coli. The gene had 1224 nucleotides and encoded a mature protein of 407 amino acid residues. The optimum pH and temperature of the purified recombinant chitosanase were 5.0 and 60 °C, respectively, and the enzyme was stable below 40 °C. The K m, V max, and specific activity of the enzyme were 1.19 mg mL(-1), 674.71 μmol min(-1) at 50 °C, and 555.3 U mg(-1), respectively. Mn(2+) was an activator of the recombinant chitosanase, while Co(2+) was an inhibitor. Hg(2+) and Cu(2+) inhibited the enzyme at 1 mM. The highest level of enzyme activity (186 U mL(-1)) was achieved in culture medium using high cell-density cultivation in a 7-L fermenter. The main products of chitosan hydrolyzed by recombinant chitosanase were (GlcN)3-6. The chitosanases was successfully secreted to the culture media through the widely used SecB-dependent type II pathway in E. coli. The high yield of the extracellular overexpression, relevant thermostability, and effective hydrolysis of commercial grade chitosan showed that this recombinant enzyme had a great potential for industrial applications.

Green synthesis approach: extraction of chitosan from fungus mycelia

Chitosan, copolymer of glucosamine and N-acetyl glucosamine is mainly derived from chitin, which is present in cell walls of crustaceans and some other microorganisms, such as fungi. Chitosan is emerging as an important biopolymer having a broad range of applications in different fields. On a commercial scale, chitosan is mainly obtained from crustacean shells rather than from the fungal sources. The methods used for extraction of chitosan are laden with many disadvantages. Alternative options of producing chitosan from fungal biomass exist, in fact with superior physico-chemical properties. Researchers around the globe are attempting to commercialize chitosan production and extraction from fungal sources. Chitosan extracted from fungal sources has the potential to completely replace crustacean-derived chitosan. In this context, the present review discusses the potential of fungal biomass resulting from various biotechnological industries or grown on negative/low cost agricultural and industrial wastes and their by-products as an inexpensive source of chitosan. Biologically derived fungal chitosan offers promising advantages over the chitosan obtained from crustacean shells with respect to different physico-chemical attributes. The different aspects of fungal chitosan extraction methods and various parameters having an effect on the yield of chitosan are discussed in detail. This review also deals with essential attributes of chitosan for high value-added applications in different fields.

Characterization of the novel antifungal chitosanase PgChP and the encoding gene from Penicillium chrysogenum

The protein PgChP is a new chitosanase produced by Penicillium chrysogenum AS51D that showed antifungal activity against toxigenic molds. Two isoforms were found by SDS-PAGE in the purified extract of PgChP. After enzymatic deglycosylation, only the smaller isoform was observed by SDS-PAGE. Identical amino acid sequences were obtained from the two isoforms. Analysis of the molecular mass by electrospray ionization-mass spectrometry revealed six major peaks from 30 to 31 kDa that are related to different levels of glycosylation. The pgchp gene has 1,146 bp including four introns and an open reading frame encoding a protein of 304 amino acids. The translated open reading frame has a predicted mass of 32 kDa, with the first 21 amino acids comprising a signal peptide. Two N glycosylation consensus sequences are present in the protein sequence. The deduced sequence showed high identity with fungal chitosanases. A high level of catalytic activity on chitosan was observed. PgChP is the first chitosanase described from P. chrysogenum. Given that enzymes produced by this mold species are granted generally recognized as safe status, PgChP could be used as a food preservative against toxigenic molds and to obtain chitosan oligomers for food additives and nutraceuticals.

Advance in chitosan hydrolysis by non-specific cellulases

Besides the specific chitinase, chitosanase and lysozyme, chitosan also could be hydrolyzed by some non-specific enzymes such as cellulase, protease, lipase and pepsin, especially cellulase, which show high activity on chitosan. Almost all the cellulases produced by different kinds of microorganisms could degrade chitosan to chitooligomers. The existence of bifunctional enzymes with cellulase and chitosanase activity is one of the reasons for cellulase on chitosan hydrolysis. The bifunctional cellulase-chitosanases mainly belong to glycoside hydrolase family 8 (GH-8), few belong to GH-5 and GH-7, according to the homogeneity analysis of amino acids sequences. Their three dimensional structures however have not been clearly determined. This paper may serve as a guide for a further study on the relationship between structure and function of chitosanolytic cellulases.

Molecular cloning, expression and characterization of a chitosanase from Microbacterium sp

A gene encoding a chitosanase (mschito) was cloned from Microbacterium sp. OU01. The ORF consists of 801 bp which encoded a polypeptide of 266 amino acid residues. The deduced amino acid sequence shows 98% identity to that of the chitosanase reported in Pseudomonas sp. A-01. In addition, the fusion protein containing MSCHITO was expressed in E. coli and purified using Ni-NTA affinity chromatography. The purified rMSCHITO protein degraded the chitosan (the degree of deacetylation of 99%) and produced a mixture of chitooligosaccharides. The MSCHITO is thus an endo-chitosanase.

Mutation breeding of chitosanase-producing strain Bacillus sp. S65 by low-energy ion implantation

In order to obtain an industrial strain with higher chitosanase yield, the wild strain Bacillus sp. S65 cells were mutated by a novel mutagen, nitrogen ion beam, with energy of 15 keV and dose ranging from 2.6 x 10(14 )to 5.2 x 10(15) ions/cm(2). One mutant, s65F5 with high yield of chitosanase was isolated. Results showed that the production of chitosanase of s65F5 was dramatically increased from 4.1 U/ml in s65 to 25 U/ml by ion beam implantation, while the fermentation time was shortened from 72 to 56 h, both of which greatly increased efficiency and reduced the cost of industrial production. Besides, the mutagenic effects of low-energy ion beam on survival rate showed characteristic down-up-down pattern, which was different from the traditional mutagens such as UV and gamma-ray and the possible mutation mechanism was discussed.