Purification and characterization of a chitinase from Serratia proteamaculans

Exposed tryptophan residues in the chitin-binding domain of ChiA74 chitinase are important for chitin-binding and antifungal activity

The chitin-binding domain (CBD) of chitinases is crucial for substrate-binding, antibacterial, and antifungal activities. Here, we constructed various mutants to investigate the role of the exposed aromatic residues of the CBD of chitinase ChiA74 from Bacillus thuringiensis. One mutant lacked the CBD, three had mutations in surface aromatic residues (W591, W626, W645), and one harbored a mutation in the hydrophobic core (W612). Compared to ChiA74, a significant decrease (∼ 40 %) in chitin and colloidal chitin binding and a negligible (∼ 6 %) decrease in cellulose binding were observed with the CBD mutant. The tryptophan mutants exhibited reduced binding to α-chitin, colloidal chitin, and cellulose, except for ChiA74W612, for which binding to cellulose remained unchanged. ChiA74 showed the highest enzymatic activity (29.429 ± 1.728 U mg-1), whereas ChiA74W645A exhibited the lowest activity (1.203 U mg-1). All mutants demonstrated a significant reduction (∼ 30 %) in antifungal activity against Fusarium oxysporum compared to ChiA74. The significance of this work lies in the data presented here, indicating that the exposed aromatic residues are crucial for substrate binding and antifungal efficacy. This creates opportunities for engineering synthetic enzymes or constructing chimeric chitinases with enhanced performance.

Marine Bacillus haynesii chitinase: Purification, characterization and antifungal potential for sustainable chitin bioconversion

The development of chitinase tailored for the bioconversion of chitin to chitin oligosaccharides has attracted significant attention due to its potential to alleviate environmental pollution associated with chemical conversion processes. In this present investigation, we purified extracellular chitinase derived from marine Bacillus haynesii to homogeneity and subsequently characterized it. The molecular weight of BhChi was approximately 35 kDa. BhChi displayed its peak catalytic activity at pH 6.0, with an optimal temperature of 37 °C. It exhibited stability across a pH range of 6.0-9.0. In addition, BhChi showed activation in the presence of Mn2+ with the improved activity of 105 U mL-1. Ca2+ and Fe2+ metal ions did not have any significant impact on enzyme activity. Under the optimized enzymatic conditions, there was a notable enhancement in catalytic activity on colloidal chitin with Km of 0.01 mg mL-1 and Vmax of 5.75 mmol min-1. Kcat and catalytic efficiency were measured at 1.91 s-1 and 191 mL mg-1 s-1, respectively. The product profiling of BhChi using thin layer chromatography and Mass spectrometric techniques hinted an exochitinase mode of action with chitobiose and N-Acetyl glucosamine as the products. This study represents the first report on an exochitinase from Bacillus haynesii. Furthermore, the chitinase showcased promising antifungal properties against key pathogens, Fusarium oxysporum and Penicillium chrysogenum, reinforcing its potential as a potent biocontrol agent.

Thermo-neutrophilic cellulases and chitinases characterized from a novel putative antifungal biocontrol agent: Bacillus subtilis TD11

Cellulose and chitin are the most abundant naturally occurring biopolymers synthesized in plants and animals and are used for synthesis of different organic compounds and acids in the industry. Therefore, cellulases and chitinases are important for their multiple uses in industry and biotechnology. Moreover, chitinases have a role in the biological control of phytopathogens. A bacterial strain Bacillus subtilis TD11 was previously isolated and characterized as a putative biocontrol agent owing to its significant antifungal potential. In this study, cellulase and chitinase produced by the strain B. subtilis TD11 were purified and characterized. The activity of the cellulases and chitinases were optimized at different pH (2 to 10) and temperatures (20 to 90°C). The substrate specificity of cellulases was evaluated using different substances including carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and crystalline substrates. The cellulase produced by B. subtilis TD11 had a molecular mass of 45 kDa while that of chitinase was 55 kDa. The optimal activities of the enzymes were found at neutral pH (6.0 to 7.0). The optimum temperature for the purified cellulases was in the range of 50 to 70°C while, purified chitinases were optimally active at 50°C. The highest substrate specificity of the purified cellulase was found for CMC (100%) followed by HEC (>50% activity) while no hydrolysis was observed against the crystalline substrates. Moreover, it was observed that the purified chitinase was inhibitory against the fungi containing chitin in their hyphal walls i.e., Rhizoctonia, Colletotrichum, Aspergillus and Fusarium having a dose-effect relationship.

Identification and Characterization of a New Serratia proteamaculans Strain That Naturally Produces Significant Amount of Extracellular Laccase

Natural biodegradation processes hold promises for the conversion of agro-industrial lignocellulosic biomaterials into biofuels and fine chemicals through lignin-degrading enzymes. The high cost and low stability of these enzymes remain a significant challenge to economic lignocellulosic biomass conversion. Wood-degrading microorganisms are a great source for novel enzyme discoveries. In this study, the decomposed wood samples were screened, and a promising γ-proteobacterial strain that naturally secreted a significant amount of laccase enzyme was isolated and identified as Serratia proteamaculans AORB19 based on its phenotypic and genotypic characteristics. The laccase activities in culture medium of strain AORB19 were confirmed both qualitatively and quantitatively. Significant cultural parameters for laccase production under submerged conditions were identified following a one-factor-at-a-time (OFAT) methodology: temperature 30°C, pH 9, yeast extract (2 g/l), Li+, Cu2+, Ca2+, and Mn2+ (0.5 mM), and acetone (5%). Under the selected conditions, a 6-fold increase (73.3 U/L) in laccase production was achieved when compared with the initial culturing conditions (12.18 U/L). Furthermore, laccase production was enhanced under alkaline and mesophilic growth conditions in the presence of metal ions and organic solvents. The results of the study suggest the promising potential of the identified strain and its enzymes in the valorization of lignocellulosic wastes. Further optimization of culturing conditions to enhance the AORB19 strain laccase secretion, identification and characterization of the purified enzyme, and heterologous expression of the specific enzyme may lead to practical industrial and environmental applications.

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.

Molecular analysis of genes involved in chitin degradation from the chitinolytic bacterium Bacillus velezensis

Bacillus velezensis RB.IBE29 is a potent biocontrol agent with high chitinase activity isolated from the rhizosphere of black pepper cultivated in the Central Highlands, Vietnam. Genome sequences revealed that this species possesses some GH18 chitinases and AA10 protein(s); however, these enzymes have not been experimentally characterized. In this work, three genes were identified from the genomic DNA of this bacterium and cloned in Escherichia coli. Sequence analysis exhibited that the ORF of chiA consists of 1,203 bp and encodes deduced 45.46 kDa-chitinase A of 400 aa. The domain structure of chitinase A is composed of a CBM 50 domain at the N-terminus and a catalytic domain at the C-terminus. The ORF of chiB includes 1,263 bp and encodes deduced 47.59 kDa-chitinase B of 420 aa. Chitinase B consists of two CBM50 domains at the N-terminus and a catalytic domain at the C-terminus. The ORF of lpmo10 is 621 bp and encodes a deduced 22.44 kDa-AA10 protein, BvLPMO10 of 206 aa. BvLPMO10 contains a signal peptide and an AA10 catalytic domain. Chitinases A and B were grouped into subfamily A of family 18 chitinases. Amino acid sequences in their catalytic domains lack aromatic residues (Trp, Phe, Tyr) probably involved in processivity and substrate binding compared with well-known bacterial GH18 chitinases. chiB was successfully expressed in E. coli. Purified rBvChiB degraded insoluble chitin and was responsible for inhibition of fungal spore-germination and egg hatching of plant-parasitic nematode. This is the first report describing the analysis of the chitinase system from B. velezensis.

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.

Identification and Characterization of a Newly Isolated Chitinase-Producing Strain Bacillus licheniformis SSCL-10 for Chitin Degradation

Chitinases or chitinolytic enzymes have different applications in the field of medicine, agriculture, and industry. The present study is aimed at developing an effective hyperchitinase-producing mutant strain of novel Bacillus licheniformis. A simple and rapid methodology was used for screening potential chitinolytic microbiota by chemical mutagenesis with ethylmethane sulfonate and irradiation with UV. There were 16 mutant strains exhibiting chitinase activity. Out of the chitinase-producing strains, the strain with maximum chitinase activity was selected, the protein was partially purified by SDS-PAGE, and the strain was identified as Bacillus licheniformis (SSCL-10) with the highest specific activity of 3.4 U/mL. The induced mutation model has been successfully implemented in the mutant EMS-13 (20.2 U/mL) that produces 5-6-fold higher yield of chitinase, whereas the mutant UV-11 (13.3 U/mL) has 3-4-fold greater chitinase activity compared to the wild strain. The partially purified chitinase has a molecular weight of 66 kDa. The wild strain (SSCL-10) was identified as Bacillus licheniformis using 16S rRNA sequence analysis. This study explores the potential applications of hyperchitinase-producing bacteria in recycling and processing chitin wastes from crustaceans and shrimp, thereby adding value to the crustacean industry.

Enhanced Tolerance against a Fungal Pathogen and Insect Resistance in Transgenic Tobacco Plants Overexpressing an Endochitinase Gene from Serratia marcescens

In this study we cloned a chitinase gene (SmchiC), from Serratia marcescens isolated from the corpse of a Diatraea magnifactella lepidopteran, which is an important sugarcane pest. The chitinase gene SmchiC amplified from the S. marcescens genome was cloned into the transformation vector p2X35SChiC and used to transform tobacco (Nicotiana tabacum L. cv Petit Havana SR1). The resistance of these transgenic plants to the necrotrophic fungus Botrytis cinerea and to the pest Spodoptera frugiperda was evaluated: both the activity of chitinase as well as the resistance against B. cinerea and S. frugiperda was significantly higher in transgenic plants compared to the wild-type.

Evaluation of the biocontrol efficacy of a Serratia marcescens strain indigenous to tea rhizosphere for the management of root rot disease in tea

The aim of the present study is to evaluate plant growth promoting and biocontrol efficacy of a Serratia marcescens strain ETR17 isolated from tea rhizosphere for the effective management of root rot disease in tea. Isolated bacterial culture ETR17 showed significant level of in vitro antagonism against nine different foliar and root pathogens of tea. The phenotypic and molecular characterization of ETR17 revealed the identity of the bacterium as Serratia marcescens. The bacterium was found to produce several hydrolytic enzymes like chitinase, protease, lipase, cellulase and plant growth promoting metabolites like IAA and siderophore. Scanning electron microscopic studies on the interaction zone between pathogen and antagonistic bacterial isolate revealed severe deformities in the fungal mycelia. Spectral analyses (LC-ESI-MS, UV-VIS spectrophotometry and HPLC) and TLC indicated the presence of the antibiotics pyrrolnitrin and prodigiosin in the extracellular bacterial culture extracts. Biofilm formation by ETR17 on polystyrene surface was also observed. In vivo application of talc-based formulations prepared with the isolate ETR17 in tea plantlets under green house conditions revealed effective reduction of root-rot disease as well as plant growth promotion to a considerable extent. Viability studies with the ETR17 talc formulation showed the survivability of the isolate up to six months at room temperature. The sustenance of ETR17 (concentration of 8-9x108 cfu g-1) in the soil after the application of talc formulation was recorded by ELISA. Safety studies revealed that ETR17 did not produce hemolysin as observed in pathogenic Serratia strains. The biocontrol strain reported in this study can be used for field application in order to minimize the use of chemical fungicides for disease control in tea gardens.

Plant Growth Promotion and Suppression of Bacterial Leaf Blight in Rice by Inoculated Bacteria

The present study was conducted to evaluate the potential of rice rhizosphere associated antagonistic bacteria for growth promotion and disease suppression of bacterial leaf blight (BLB). A total of 811 rhizospheric bacteria were isolated and screened against 3 prevalent strains of BLB pathogen Xanthomonas oryzae pv. oryzae (Xoo) of which five antagonistic bacteria, i.e., Pseudomonas spp. E227, E233, Rh323, Serratia sp. Rh269 and Bacillus sp. Rh219 showed antagonistic potential (zone of inhibition 1-19 mm). Production of siderophores was found to be the common biocontrol determinant and all the strains solubilized inorganic phosphate (82-116 μg mL-1) and produced indole acetic acid (0.48-1.85 mg L-1) in vitro. All antagonistic bacteria were non-pathogenic to rice, and their co-inoculation significantly improved plant health in terms of reduced diseased leaf area (80%), improved shoot length (31%), root length (41%) and plant dry weight (60%) as compared to infected control plants. Furthermore, under pathogen pressure, bacterial inoculation resulted in increased activity of defense related enzymes including phenylalanine ammonia-lyase and polyphenol oxidase, along with 86% increase in peroxidase and 53% increase in catalase enzyme activities in plants inoculated with Pseudomonas sp. Rh323 as well as co-inoculated plants. Bacterial strains showed good colonization potential in the rice rhizosphere up to 21 days after seed inoculation. Application of bacterial consortia in the field resulted in an increase of 31% in grain yield and 10% in straw yield over non-inoculated plots. Although, yield increase was statistically non-significant but was accomplished with overall saving of 20% chemical fertilizers. The study showed that Pseudomonas sp. Rh323 can be used to develop dual-purpose inoculum which can serve not only to suppress BLB but also to promote plant growth in rice.

The role of the chi1 gene from the endophytic bacteria Serratia proteamaculans 336x in the biological control of wheat take-all

Take-all, a disease caused by the fungus Gaeumannomyces graminis var. tritici, is the most important root disease of wheat and causes severe yield losses worldwide. Using microorganisms as biological agents to control the disease is important because no resistant cultivars or effective chemical fungicides are available. In this study, we tested the biological control capability of a chitinase produced by the endophytic bacterium Serratia proteamaculans 336x against wheat take-all. The chitinase gene chi1 of S. proteamaculans 336x was cloned and heterologously expressed in Escherichia coli. The recombinant protein exhibited chitinase activity and in vitro antifungal activity against G. graminis var. tritici. With in-frame deletion of the chi1 gene by homologous recombination, the chi1-deleted mutant was devoid of chitinase activity and the biocontrol efficacy was reduced by 42.5%. The complementation of the Δchi1 mutant strain by the chi1 gene resulted in the partial restoration of the chitinase activity and biocontrol efficacy. These results support a role for the Chi1 protein in the biocontrol process of S. proteamaculans 336x against wheat take-all.

Comparative genome analysis of Enterobacter cloacae

The Enterobacter cloacae species includes an extremely diverse group of bacteria that are associated with plants, soil and humans. Publication of the complete genome sequence of the plant growth-promoting endophytic E. cloacae subsp. cloacae ENHKU01 provided an opportunity to perform the first comparative genome analysis between strains of this dynamic species. Examination of the pan-genome of E. cloacae showed that the conserved core genome retains the general physiological and survival genes of the species, while genomic factors in plasmids and variable regions determine the virulence of the human pathogenic E. cloacae strain; additionally, the diversity of fimbriae contributes to variation in colonization and host determination of different E. cloacae strains. Comparative genome analysis further illustrated that E. cloacae strains possess multiple mechanisms for antagonistic action against other microorganisms, which involve the production of siderophores and various antimicrobial compounds, such as bacteriocins, chitinases and antibiotic resistance proteins. The presence of Type VI secretion systems is expected to provide further fitness advantages for E. cloacae in microbial competition, thus allowing it to survive in different environments. Competition assays were performed to support our observations in genomic analysis, where E. cloacae subsp. cloacae ENHKU01 demonstrated antagonistic activities against a wide range of plant pathogenic fungal and bacterial species.

Friend or foe? A review of the mechanisms that driveSerratiatowards diverse lifestyles

Found widespread around the globe, Serratia are Gram-negative bacteria capable of thriving in a diverse number of environments that include water, soil, and the digestive tracts of various animals. Known for their ability to produce a myriad of extracellular enzymes, these bacteria also produce various secondary metabolites that directly contribute to their survival. While the effects Serratia species have on other organisms range from parasitic to symbiotic, what these bacteria have in common is their ability to resist attack, respond appropriately to environmental conditions, and outcompete other microorganisms when colonizing their respective niche. This review highlights the mechanisms utilized by Serratia species that drive their ubiquitous nature, with emphasis on the latest findings. Also discussed is how secreted compounds drive these bacteria towards pathogenic, mutualistic, and antagonistic associations.

Chitinases: in agriculture and human healthcare

Biological control of phytopathogenic fungi and insects continues to inspire the research and development of environmentally friendly bioactive alternatives. Potentially lytic enzymes, chitinases can act as a biocontrol agent against agriculturally important fungi and insects. The cell wall in fungi and protective covers, i.e. cuticle in insects shares a key structural polymer, chitin, a β-1,4-linked N-acetylglucosamine polymer. Therefore, it is advantageous to develop a common biocontrol agent against both of these groups. As chitin is absent in plants and mammals, targeting its metabolism will signify an eco-friendly strategy for the control of agriculturally important fungi and insects but is innocuous to mammals, plants, beneficial insects and other organisms. In addition, development of chitinase transgenic plant varieties probably holds the most promising method for augmenting agricultural crop protection and productivity, when properly integrated into traditional systems. Recently, human proteins with chitinase activity and chitinase-like proteins were identified and established as biomarkers for human diseases. This review covers the recent advances of chitinases as a biocontrol agent and its various applications including preparation of medically important chitooligosaccharides, bioconversion of chitin as well as in implementing chitinases as diagnostic and prognostic markers for numerous diseases and the prospect of their future utilization.

Chitinase A from Stenotrophomonas maltophilia shows transglycosylation and antifungal activities

Stenotrophomonas maltophilia chitinase (StmChiA and StmChiB) genes were cloned and expressed as soluble proteins of 70.5 and 41.6 kDa in Escherichia coli. Ni-NTA affinity purified StmChiA and StmChiB were optimally active at pH 5.0 and 7.0, respectively and exhibited broad range pH activity. StmChiA and StmChiB had an optimum temperature of 40°C and are stable up to 50 and 40°C, respectively. Hydrolytic activity on chitooligosaccharides indicated that StmChiA was an endo-acting enzyme releasing chitobiose and StmChiB was both exo/endo-acting enzyme with the release of GlcNAc as the final product. StmChiA showed higher preference to β-chitin and exhibited transglycosylation on even chain length tetra- and hexameric substrates. StmChiA, and not StmChiB, was active on chitinous polymers and showed antifungal activity against Fusarium oxysporum.

Characterization of a chitinase (Chit62) from Serratia marcescens B4A and its efficacy as a bioshield against plant fungal pathogens

Chitinases have been suggested to be involved in pathogen-antagonist interaction during biological control progress of plant pathogenic fungi. Here, a recombinant bacterial chitinase originally from Serratia marcescens B4A was produced, purified, and assayed biochemically to ascertain the activity and determine the kinetics parameters. Active enzyme was used to determine its biocontrol features against fungal phytopathogens. The results demonstrated that the optimum pH and temperature for the enzyme activity were 6.0 and 55 °C, respectively. The K(m) and V(max) values were 3.30 mg ml(-1) and 0.92 units, respectively. The recombinant chitinase was demonstrated to be highly active in controlling fungal pathogens.

Multiple chitinases of an endophytic Serratia proteamaculans 568 generate chitin oligomers

Serratia proteamaculans 568 genome revealed the presence of four family 18 chitinases (Sp ChiA, Sp ChiB, Sp ChiC, and Sp ChiD). Heterologous expression and characterization of Sp ChiA, Sp ChiB, and Sp ChiC showed that these enzymes were optimally active at pH 6.0-7.0, and 40°C. The three Sp chitinases displayed highest activity/binding to β-chitin and showed broad range of substrate specificities, and released dimer as major end product from oligomeric and polymeric substrates. Longer incubation was required for hydrolysis of trimer for the three Sp chitinases. The three Sp chitinases released up to tetramers from colloidal chitin substrate. Sp ChiA and Sp ChiB were processive chitinases, while Sp ChiC was a non-processive chitinase. Based on the known structures of ChiA and ChiB from S. marcescens, 3D models of Sp ChiA and Sp ChiB were generated.

Molecular characterization of the modular chitin binding protein Cbp50 from Bacillus thuringiensis serovar konkukian

Bacillus thuringiensis is an insecticidal bacterium whose chitinolytic system may be exploited to improve the insecticidal system of Bt-crops. A nucleotide fragment of 1368 bp from B. thuringiensis serovar konkukian S4, containing the complete coding sequence of the chitin binding protein Cbp50, was cloned and sequenced. Analyses have shown the protein to contain a modular structure consisting of an N-terminal CBM33 domain, two copies of a fibronectin-like domain and a C-terminal chitin binding domain classified as CBM5. The Cbp50 protein was heterologously expressed in Escherichia coli, purified and assessed for chitin binding activity. A deletion mutant (CBD-N; containing only the N-terminal CBM33 domain) of Cbp50 was produced to determine the role of C-terminal domains in the binding activity of the protein. The full-length Cbp50 was shown to bind β-chitin most efficiently followed by α-chitin, colloidal chitin and cellulose. The polysaccharide binding activity of CBD-N was drastically decreased. The data demonstrate that both the N-terminal and C-terminal domains of Cbp50 are essential for the efficient binding of chitin. The purified Cbp50 showed antifungal activity against the phytopathogenic fungus Fusarium oxysporum and the opportunistic human pathogen Aspergillus niger. This is the first report of a modular chitin binding protein in bacteria.

Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.