Partial purification and characterization of chiIO8, a novel antifungal chitinase produced by Bacillus cereus IO8

Bacillus cereus sensu lato antimicrobial arsenal: An overview

The Bacillus cereus group contains genetically closed bacteria displaying a variety of phenotypic features and lifestyles. The group is mainly known through the properties of three major species: the entomopathogen Bacillus thuringiensis, the animal and human pathogen Bacillus anthracis and the foodborne opportunistic strains of B. cereus sensu stricto. Yet, the actual diversity of the group is far broader and includes multiple lifestyles. Another less-appreciated aspect of B. cereus members lies within their antimicrobial potential which deserves consideration in the context of growing emergence of resistance to antibiotics and pesticides, and makes it crucial to find new sources of antimicrobial molecules. This review presents the state of knowledge on the known antimicrobial compounds of the B. cereus group members, which are grouped according to their chemical features and biosynthetic pathways. The objective is to provide a comprehensive review of the antimicrobial range exhibited by this group of bacteria, underscoring the interest in its potent biocontrol arsenal and encouraging further research in this regard.

The Prospect of Hydrolytic Enzymes from Bacillus Species in the Biological Control of Pests and Diseases in Forest and Fruit Tree Production

Plant diseases and insect pest damage cause tremendous losses in forestry and fruit tree production. Even though chemical pesticides have been effective in the control of plant diseases and insect pests for several decades, they are increasingly becoming undesirable due to their toxic residues that affect human life, animals, and the environment, as well as the growing challenge of pesticide resistance. In this study, we review the potential of hydrolytic enzymes from Bacillus species such as chitinases, β-1,3-glucanases, proteases, lipases, amylases, and cellulases in the biological control of phytopathogens and insect pests, which could be a more sustainable alternative to chemical pesticides. This study highlights the application potential of the hydrolytic enzymes from different Bacillus sp. as effective biocontrol alternatives against phytopathogens/insect pests through the degradation of cell wall/insect cuticles, which are mainly composed of structural polysaccharides like chitins, β-glucans, glycoproteins, and lipids. This study demonstrates the prospects for applying hydrolytic enzymes from Bacillus sp. as effective biopesticides in forest and fruit tree production, their mode of biocidal activity and dual antimicrobial/insecticidal potential, which indicates a great prospect for the simultaneous biocontrol of pests/diseases. Further research should focus on optimizing the production of hydrolytic enzymes, and the antimicrobial/insecticidal synergism of different Bacillus sp. which could facilitate the simultaneous biocontrol of pests and diseases in forest and fruit tree production.

Plant Growth Promotion Using Bacillus cereus

Plant growth-promoting bacteria (PGPB) appear to be a sensible competitor to conventional fertilization, including mineral fertilizers and chemical plant protection products. Undoubtedly, one of the most interesting bacteria exhibiting plant-stimulating traits is, more widely known as a pathogen, Bacillus cereus. To date, several environmentally safe strains of B. cereus have been isolated and described, including B. cereus WSE01, MEN8, YL6, SA1, ALT1, ERBP, GGBSTD1, AK1, AR156, C1L, and T4S. These strains have been studied under growth chamber, greenhouse, and field conditions and have shown many significant traits, including indole-3-acetic acid (IAA) and aminocyclopropane-1-carboxylic acid (ACC) deaminase production or phosphate solubilization, which allows direct plant growth promotion. It includes an increase in biometrics traits, chemical element content (e.g., N, P, and K), and biologically active substances content or activity, e.g., antioxidant enzymes and total soluble sugar. Hence, B. cereus has supported the growth of plant species such as soybean, maize, rice, and wheat. Importantly, some B. cereus strains can also promote plant growth under abiotic stresses, including drought, salinity, and heavy metal pollution. In addition, B. cereus strains produced extracellular enzymes and antibiotic lipopeptides or triggered induced systemic resistance, which allows indirect stimulation of plant growth. As far as biocontrol is concerned, these PGPB can suppress the development of agriculturally important phytopathogens, including bacterial phytopathogens (e.g., Pseudomonas syringae, Pectobacterium carotovorum, and Ralstonia solanacearum), fungal phytopathogens (e.g., Fusarium oxysporum, Botrytis cinerea, and Rhizoctonia solani), and other phytopathogenic organisms (e.g., Meloidogyne incognita (Nematoda) and Plasmodiophora brassicae (Protozoa)). In conclusion, it should be noted that there are still few studies on the effectiveness of B. cereus under field conditions, particularly, there is a lack of comprehensive analyses comparing the PGP effects of B. cereus and mineral fertilizers, which should be reduced in favor of decreasing the use of mineral fertilizers. It is also worth mentioning that there are still very few studies on the impact of B. cereus on the indigenous microbiota and its persistence after application to soil. Further studies would help to understand the interactions between B. cereus and indigenous microbiota, subsequently contributing to increasing its effectiveness in promoting plant growth.

Microbial chitinases and their relevance in various industries

Chitin, the second most abundant biopolymer on earth after cellulose, is composed of β-1,4-N-acetylglucosamine (GlcNAc) units. It is widely distributed in nature, especially as a structural polysaccharide in the cell walls of fungi, the exoskeletons of crustaceans, insects, and nematodes. However, the principal commercial source of chitin is the shells of marine or freshwater invertebrates. Microbial chitinases are largely responsible for chitin breakdown in nature, and they play an important role in the ecosystem's carbon and nitrogen balance. Several microbial chitinases have been characterized and are gaining prominence for their applications in various sectors. The current review focuses on chitinases of microbial origin, their diversity, and their characteristics. The applications of chitinases in several industries such as agriculture, food, the environment, and pharmaceutical sectors are also highlighted.

Kinetic, Thermodynamic and Bio-applicable Studies on Aspergillus niger Mk981235 Chitinase

Chitinases have many applications in food, agricultural, medical, and pharmaceutical fields. This study succeeded in investigating Aspergillus niger MK981235 chitinase in the spot of its physiochemical, kinetic, thermodynamic, and application. The optimum temperature, pH and p-nitrophenyl-β-d-N-acetyl glucosaminide (PNP-β-GlcNAc) concentration to obtain the highest chitinase activity of 2334.79 U ml−1 were at 60 °C, 5 and 0.25%, respectively. The kinetic parameters, including Km and Vmax were determined to be 0.78 mg ml−1 and 2222.22 µmol ml−1 min−1, respectively. Furthermore, the thermodynamic parameters T1/2, D-values, ΔH, ΔG and ΔS at 40, 50 and 60 °C were determined to be (864.10, 349.45, 222.34 min), (2870.99, 1161.07, 738.74 min), (126.40, 126.36, 126.32 kJ mol−1), (101.59, 100.62, 100.86 kJ mol−1), (74.50, 76.17, 47.24 J mol−1 K−1), respectively. A. niger chitinase showed, insecticidal activity on Galleria mellonella by feeding and spraying treatments (72 and 52%, respectively), anti-lytic activity against Candida albicans, and effectiveness in improving the dye removal in the presence of crab shell powder as bio-absorbant. A. niger chitinase can be used in the pharmaceutical field for the bio-control of diseases caused by C. albicans and for the pretreatment of wastewater from the textile industry.

Graphical Abstract

Formation of recombinant bifunctional fusion protein: A newer approach to combine the activities of two enzymes in a single protein

The tissue of insects, pests, and fungi has a chitin layer followed by protein in the cell membrane. The complete biodegradation of chitin and protein-present in the waste requires the action of two enzymes, namely chitinase, and protease. Combining chitinase and protease in a single protein/enzyme will serve as a bifunctional enzyme that can efficiently degrade the chitin and protein-rich biomass. The present study was aimed to fuse these two enzymes to produce a single protein and study the kinetics of the recombinant fusion protein. A chitinase and alkaline protease genes were isolated, cloned, and expressed successfully as a fusion product in heterologous host Escherichia coli. The two native genes were successfully fused in E.coli by using flexible glycine–serine (G₄S)₂ linker (GGGGS, GS linker). The recombinant fusion protein in E.coli showed hydrolyzed chitin and protein on chitin and bovine serum albumin agar plates confirming the successful cloning and expression of chitinase and protease enzymes in a single fusion protein. The common pUC18-T7 mini vector with the ompA signal sequence helps the extracellular expression of fusion protein efficiently. The native gel electrophoresis revealed a molecular mass of purified protein as 92.0 kDa. The fusion protein’s maximal chitinase and protease activity occurred at pH 5.0 and 8.0 and 30 ⁰C, respectively resembling the individual enzymes’. In the kinetic studies of the fusion protein, it was observed that the presence of metal ions such as Cu²⁺, Na²⁺, and Ca²⁺; significantly enhanced the enzyme activities while organic solvents oxidants and chemicals have drastically affected the activities of both the enzymes in the fusion protein. No such fusion protein has been produced in a heterologous host yet. The reports on fusion protein with biomass-degrading capacity are also scarce. This is probably the first report of a bifunctional chitinase/protease expressed in E. coli.

A Contemporary Appraisal on Impending Industrial and Agricultural Applications of Thermophilic-Recombinant Chitinolytic Enzymes from Microbial Sources

The ability of chitinases to degrade the second most abundant polymer, chitin, into potentially useful chitooligomers and chitin derivatives has not only rendered them fit for chitinous waste management but has also made them important from industrial point of view. At the same time, they have also been recognized to have an imperative role as promising biocontrol agents for controlling plant diseases. As thermostability is an important property for an industrially important enzyme, various bacterial and fungal sources are being exploited to obtain such stable enzymes. These stable enzymes can also play a role in agriculture by maintaining their stability under adverse environmental conditions for longer time duration when used as biocontrol agent. Biotechnology has also played its role in the development of recombinant chitinases with enhanced activity, thermostability, fungicidal and insecticidal activity via recombinant DNA techniques. Furthermore, a relatively new approach of generating pathogen-resistant transgenic plants has opened new ways for sustainable agriculture by minimizing the yield loss of valuable crops and plants. This review focuses on the potential applications of thermostable and recombinant microbial chitinases in industry and agriculture.

Heterologous Expression of a Thermostable Chitinase from Myxococcus xanthus and Its Application for High Yield Production of Glucosamine from Shrimp Shell

Glucosamine (GlcN) is a widely used food supplement. Hence, enormous attention has been concerned with enzymatic production of GlcN owing to its advantage over a chemical approach. In this study, a previously unstudied chitinase gene (MxChi) in the genome of Myxococcus xanthus was cloned, expressed in recombinant soluble form and purified to homogeneity. TLC-, UPLC-, and microplate-reader- based activity tests confirmed MxChi hydrolyzes colloidal chitin to chitobiose as sole product. The optimal catalytic pH and temperature of MxChi was identified as 7.0 and 55 °C, respectively. MxChi exhibited 80% activity after 72 h incubation at 37 °C. The site-directed mutagenesis revealed that the amino acids D323A, D325A, and E327A of MxChi were in the DXDXE catalytic motif of GH18. When coupled with β-N-acetylhexosaminidase (SnHex) and deacetylase (CmCBDA), the enzyme allowed one-pot extraction of GlcN from colloidal chitin and shrimp shell. The optimal condition was 37 °C, pH 8.0, and 1/3/16.5 (MxChi/SnHex/CmCBDA), conducted by orthogonal design for the enzymatic cascades. Under this condition, the yield of GlcN was 26.33 mg from 400 mg shrimp shell. Facile recombinant in E. coli, robust thermostability and pure product herein makes newly discovered chitinase a valuable candidate for the green recycling of chitin rich waste.

Molecular cloning, heterologous expression, and in silico sequence analysis of Enterobacter GH19 class I chitinase (chiRAM gene)

BACKGROUND

Using in silico sequence analyses, the present study aims to clone and express the gene-encoding sequence of a GH19 chitinase from Enterobacter sp. in Escherichia coli.

METHODS AND RESULTS

The putative open reading frame of a GH19 chitinase from Enterobacter sp. strain EGY1 was cloned and expressed into pGEM®-T and pET-28a (+) vectors, respectively using a degenerate primer. The isolated nucleotide sequence (1821 bp, GenBank accession no.: MK533791.2) was translated to a chiRAM protein (606 amino acids, UniProt accession no.: A0A4D6J2L9). The in silico protein sequence analysis of chiRAM revealed a class I GH19 chitinase: an N-terminus signal peptide (Met¹-Ala²³), a catalytic domain (Val⁸³-Glu³⁴⁷ and the catalytic triad Glu¹⁴⁹, Glu¹⁷¹, and Ser²¹⁸), a proline-rich hinge region (Pro⁴¹⁴ -Pro⁴⁵⁰), a polycystic kidney disease protein motif (Gly ⁴⁶⁵-Ser ⁵³³), a C-terminus chitin-binding domain (Ala⁵⁵³- Glu⁵⁹³), and conserved class I motifs (NYNY and AQETGG). A three-dimensional model was constructed by LOMETS MODELLER of PDB template: 2dkvA (class I chitinase of Oryza sativa L. japonica). Recombinant chiRAM was overexpressed as inclusion bodies (IBs) (~ 72 kDa; SDS-PAGE) in 1.0 mM IPTG induced E. coli BL21 (DE3) Rosetta strain at room temperature 18 h after induction. Optimized expression yielded active chiRAM with 1.974 ± 0.0002 U/mL, on shrimp colloidal chitin (SCC), in induced E. coli BL21 (DE3) Rosetta cells growing in SB medium. LC-MS/MS identified a band of 72 kDa in the soluble fraction with a 52.3% coverage sequence exclusive to the GH19 chitinase of Enterobacter cloacae (WP_063869339.1).

CONCLUSIONS

Although chiRAM of Enterobacter sp. was successfully cloned and expressed in E. coli with appreciable chitinase activity, future studies should focus on minimizing IBs to facilitate chiRAM purification and characterization.

Isolation and Molecular Identification of Two Chitinase Producing Bacteria from Marine Shrimp Shell Wastes

BACKGROUND AND OBJECTIVE

Chitinase enzymes have a various application in the field of environmental, biotechnology and medical aspects. This study aimed to the production of the chitinolytic enzymes from different species of bacteria.

MATERIALS AND METHODS

Bacterial isolation from different habitats was carried out on agar medium containing chitin as carbon and nitrogen sources. The obtained bacteria (20) were characterized and screened again in chitin broth medium.

RESULTS

Out of 20 bacterial isolate, 2 new isolates, belonged to Streptomyces laurentii SN5 and Cellulosimicrobium funkei SN20, were the most active in chitin degradation compared to the other isolates. They have been characterized for the first time for their chitinase activity. They were identified using 16S rRNA gene analysis and in the liquid medium, the 2 isolates have enzyme activities of 0.533 and 0.537 U mL-1, respectively. The maximum chitinase production was obtained when those bacterial strains were grown in Luria-Bertani (LB) broth amended with 1% colloidal chitin, for 1 day and at temperature of 30°C. The optimum pH value for chitinase production was pH 7 for both S. laurentii and C. funkei. The enzyme has been purified using Sephadex G-100 and DEAE-Cellulose chromatography column and found to have a similar molecular size of ~50 kDa.

CONCLUSION

Those two bacterial species could be used in chitinase production and in the environmental recycling of disposable chitin wastes such as chitin from shrimp shell waste.

Complete Genome Sequence of Brevibacillus laterosporus Bl-zj, an Algicidal Bacterium Isolated from Soil

Brevibacillus laterosporus can be used as a biocontrol agent for varieties of plants, as it is a pathogen of invertebrates and can also inhibit many bacteria and fungi. Here, we describe the complete genome sequence of B. laterosporus strain Bl-zj, an algicidal bacterium on cyanobacteria isolated from the soil in China.

Cloning, purification, and characterization of an organic solvent-tolerant chitinase, MtCh509, from Microbulbifer thermotolerans DAU221

BACKGROUND

The ability to use organic solvents in enzyme reactions offers a number of industrially useful advantages. However, most enzymes are almost completely inactive in the presence of organic solvents. Thus, organic solvent-tolerant enzymes have potential applications in industrial processes.

RESULTS

A chitinase gene from Microbulbifer thermotolerans DAU221 (mtch509) was cloned and expressed in Escherichia coli BL21 (DE3). The molecular weight of the expressed MtCh509 protein was approximately 60 kDa, and it was purified by His-tag affinity chromatography. Enzymatic assays showed that the optimum temperature for MtCh509 chitinase activity was 55 °C, and the enzyme was stable for 2 h at up to 50 °C. The optimum pH for MtCh509 activity was in the sub-acidic range, at pH 4.6 and 5.0. The activity of MtCh509 was maintained in presence of 1 M salt, gradually decreasing at higher concentrations, with residual activity (20%) detected after incubation in 5 M salt. Some organic solvents (benzene, DMSO, hexane, isoamyl alcohol, isopropyl alcohol, and toluene; 10-20%, v/v) increased the reactivity of MtCh509 relative to the aqueous system. When using NAG3, as a substrate, MtCh509 produced NAG2 as the major product, as well as NAG4, demonstrating that MtCh509 has transglycosylation activity. The K m and V max values for MtCh509 using colloidal chitin as a substrate were 9.275 mg/mL and 20.4 U/mg, respectively. Thus, MtCh509 could be used in extreme industrial conditions.

CONCLUSION

The results of the hydrolysate analysis and the observed increase in enzyme activity in the presence of organic solvents show that MtCh509 has industrially attractive advantages. This is the first report on an organic solvent-tolerant and transglycosylating chitinase from Microbulbifer species.

Cloning, characterization and substrate degradation mode of a novel chitinase from Streptomyces albolongus ATCC 27414

A novel chitinase gene was cloned from Streptomyces albolongus ATCC 27414, and expressed successfully in Escherichia coli BL21. The recombinant enzyme (SaChiA4) belongs to glycoside hydrolases (GH) family 18 and consists of a catalytic domain and a chitin binding domain (CBD) in its C-terminus. SaChiA4 was purified homogeneously (specific activity of 66.2 U/mg with colloidal chitin as substrate), and showed a molecular mass of approximately 47 kDa. SaChiA4 showed its optimal activity at pH 5.0 and 55 °C and exhibited remarkable pH and temperature stability. SaChiA4 has been proved to have a higher specificity toward glycosides containing acetyl groups and hydrolyzes the substrates in a non-processive manner with higher ability to produce (GlcNAc)₂ and GlcNAc. The results indicated that SaChiA4 is a novel endo-type chitinase, which has potential applications in the treatment of chitin wastes and the production of (GlcNAc)₂.

Display of B. pumilus chitinase on the surface of B. subtilis spore as a potential biopesticide

BACKGROUND

Chitinases can inhibit the growth of many fungal diseases which are a great threat for global agricultural production. Biological control of pathogens like fungi, is believed to be one of the best ways to eliminate the adverse effects of plant pathogens. To this end, we expressed and displayed a chitinase from Bacillus pumilus (ChiS) on the surface of Bacillus subtilis spores, as a biocontrol agent.

RESULT

ChiS enzyme from B. pumilus was expressed on the spores of B. subtilis using CotG as a carrier protein. Immunofluorescence microscopy confirmed the expression of ChiS on the surface of the spores. Enzyme activity assay showed that the surface displayed ChiS was active and was also able to inhibit the growth of Rhizoctonia solani and Trichoderma harzianum fungi. Western blot analysis also indicated that CotG-ChiS is partially processed after display. Molecular dynamics simulation showed that the stability of the heterologous protein was decreased after fusion.

CONCLUSION

ChiS was successfully displayed on the surface of Bacillus spores by fusion to the CotG, one of the main spore coat proteins. In-vitro experiments showed that the displayed enzyme was effective in growth inhibition of R. solani and T. harzianum fungi.

Transglycosylation by a chitinase from Enterobacter cloacae subsp. cloacae generates longer chitin oligosaccharides

Humans have exploited natural resources for a variety of applications. Chitin and its derivative chitin oligosaccharides (CHOS) have potential biomedical and agricultural applications. Availability of CHOS with the desired length has been a major limitation in the optimum use of such natural resources. Here, we report a single domain hyper-transglycosylating chitinase, which generates longer CHOS, from Enterobacter cloacae subsp. cloacae 13047 (EcChi1). EcChi1 was optimally active at pH 5.0 and 40 °C with a K_m of 15.2 mg ml⁻¹, and k_cat/K_m of 0.011× 10² mg⁻¹ ml min⁻¹ on colloidal chitin. The profile of the hydrolytic products, major product being chitobiose, released from CHOS indicated that EcChi1 was an endo-acting enzyme. Transglycosylation (TG) by EcChi1 on trimeric to hexameric CHOS resulted in the formation of longer CHOS for a prolonged duration. EcChi1 showed both chitobiase and TG activities, in addition to hydrolytic activity. The TG by EcChi1 was dependent, to some extent, on the length of the CHOS substrate and concentration of the enzyme. Homology modeling and docking with CHOS suggested that EcChi1 has a deep substrate-binding groove lined with aromatic amino acids, which is a characteristic feature of a processive enzyme.

Biocontrol potential of Halotolerant bacterial chitinase from high yielding novel Bacillus Pumilus MCB-7 autochthonous to mangrove ecosystem

The multifaceted role of chitinase in medicine, agriculture, environmental remediation and various other industries greatly demands the isolation of high yielding chitinase producing microorganisms with improved properties. The current study aimed to investigate the isolation, characterization and biocontrol prospective of chitinase producing bacterial strains autochthonous to the extreme conditions of mangrove ecosystems. Among the 51 bacterial isolates screened, Bacillus pumilus MCB-7 with highest chitinase production potential was identified and confirmed by 16S rDNA typing. Chitinase enzyme of MCB-7 was purified; the chitin degradation was evaluated by SEM and LC-MS. Unlike previously reported B.pumilus isolates, MCB-7 exhibited highest chitinase activity of 3.36U/mL, active even at high salt concentrations and temperature up to 60°C. The crude as well as purified enzyme showed significant antimycotic activity against agricultural pathogens such as Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, Ceratorhiza hydrophila and Fusarium oxysporum. The enzyme also exhibited biopesticidal role against larvae of Scirpophaga incertulas (Walker). [Lep.: Pyralidae], a serious agricultural pest of rice. The high chitinolytic and antimycotic potential of MCB-7 increases the prospects of the isolate as an excellent biocontrol agent. To the best of our knowledge, this is the first report of high chitinase yielding Bacillus pumilus strain from mangrove ecosystem with a biocontrol role against phytopathogenic fungi and insect larval pests.

Antifungal chitinase against human pathogenic yeasts from Coprinellus congregatus

The inky cap, Coprinellus congregatus, produces mushrooms which become autolyzed rapidly to generate black liquid droplets, in which no cell wall is detected by microscopy. A chitinase (Chi2) which is synthesized during the autolytic phase of C. congregatus inhibits the growths of Candida albicans and Cryptococcus neoformans up to 10% at the concentration of 10 μg/ml, about 50% at concentration of 20 μg/ml, and up to 95% at the concentration of 70 μg/ml. Upon treatment these yeast cells are observed to be severely deformed, with the formation of large holes in the cell wall. The two yeast species show no growth inhibition at the concentration of 5 μg/ml, which means the minimum inhibitory concentrations for both yeast species are 10 μg/ml under these experimental conditions.

An acidic, thermostable exochitinase with β-N-acetylglucosaminidase activity from Paenibacillus barengoltzii converting chitin to N-acetyl glucosamine

BACKGROUND

N-acetyl-β-D-glucosamine (GlcNAc) is widely used as a valuable pharmacological agent and a functional food additive. The traditional chemical process for GlcNAc production has some problems such as high production cost, low yield, and acidic pollution. Hence, to identify a novel chitinase that is suitable for bioconversion of chitin to GlcNAc is of great value.

RESULTS

A novel chitinase gene (PbChi74) from Paenibacillus barengoltzii was cloned and heterologously expressed in Escherichia coli as an intracellular soluble protein. The gene has an open reading frame (ORF) of 2,163 bp encoding 720 amino acids. The recombinant chitinase (PbChi74) was purified to apparent homogeneity with a purification fold of 2.2 and a recovery yield of 57.9%. The molecular mass of the purified enzyme was estimated to be 74.6 kDa and 74.3 kDa by SDS-PAGE and gel filtration, respectively. PbChi74 displayed an acidic pH optimum of 4.5 and a temperature optimum of 65°C. The enzyme showed high activity toward colloidal chitin, glycol chitin, N-acetyl chitooligosaccharides, and p-nitrophenyl N-acetyl β-glucosaminide. PbChi74 hydrolyzed colloidal chitin to yield N-acetyl chitobiose [(GlcNAc)2] at the initial stage, which was further converted to its monomer N-acetyl glucosamine (GlcNAc), suggesting that it is an exochitinase with β-N-acetylglucosaminidase activity. The purified PbChi74 coupled with RmNAG (β-N-acetylglucosaminidase from Rhizomucor miehei) was used to convert colloidal chitin to GlcNAc, and GlcNAc was the sole end product at a concentration of 27.8 mg mL(-1) with a conversion yield of 92.6%. These results suggest that PbChi74 may have great potential in chitin conversion.

CONCLUSIONS

The excellent thermostability and hydrolytic properties may give the exochitinase great potential in GlcNAc production from chitin. This is the first report on an exochitinase with N-acetyl-β-D-glucosaminidase activity from Paenibacillus species.

Chitinolytic microorganisms and their possible application in environmental protection

This paper provides a review of the latest research findings on the applications of microbial chitinases to biological control. Microorganisms producing these enzymes can inhibit the growth of many fungal diseases that pose a serious threat to global crop production. Currently, efforts are being made to discover producers of chitinolytic enzymes. The potential exists that natural biofungicides will replace chemical fungicides or will be used to supplement currently used fungicides, which would reduce the negative impact of chemicals on the environment and support the sustainable development of agriculture and forestry.