Gene Cloning, Heterologous Expression, and In Silico Analysis of Chitinase B from Serratia marcescens for Biocontrol of Spodoptera frugiperda Larvae Infesting Maize Crops.

Spodoptera frugiperda, the fall armyworm (FAW), is a highly invasive polyphagous insect pest that is considered a source of severe economic losses to agricultural production. Currently, the majority of chemical insecticides pose tremendous threats to humans and animals besides insect resistance. Thus, there is an urgent need to develop new pest management strategies with more specificity, efficiency, and sustainability. Chitin-degrading enzymes, including chitinases, are promising agents which may contribute to FAW control. Chitinase-producing microorganisms are reported normally in bacteria and fungi. In the present study, Serratia marcescens was successfully isolated and identified from the larvae of Spodoptera frugiperda. The bacterial strain NRC408 displayed the highest chitinase enzyme activity of 250 units per milligram of protein. Subsequently, the chitinase gene was cloned and heterologously expressed in E. coli BL21 (DE3). Recombinant chitinase B was overproduced to 2.5-fold, driven by the T7 expression system. Recombinant chitinase B was evaluated for its efficacy as an insecticidal bioagent against S. frugiperda larvae, which induced significant alteration in subsequent developmental stages and conspicuous malformations. Additionally, our study highlights that in silico analyses of the anticipated protein encoded by the chitinase gene (ChiB) offered improved predictions for enzyme binding and catalytic activity. The effectiveness of (ChiB) against S. frugiperda was evaluated in laboratory and controlled field conditions. The results indicated significant mortality, disturbed development, different induced malformations, and a reduction in larval populations. Thus, the current study consequently recommends chitinase B for the first time to control FAW.

Heterologous expression and characterization of an antifungal chitinase (Chit46) from Trichoderma harzianum GIM 3.442 and its application in colloidal chitin conversion.

In this study, a chitinase gene, Chit46 from a mycoparasitic fungus Trichoderma harzianum was successfully expressed in Pichia pastoris with a high heterologous chitinase production of 31.4 U/mL, much higher than the previous reports. The active center and substrate binding pocket of the recombinant Chit46 (rChit46) were analyzed and the effects of pH, temperature, metal ions and glycosylation on its activity were tested. rChit46 effectively hydrolyzed colloidal chitin with a high conversion rate of 80.5% in 3 h and the chitin hydrolysates were mainly composed of (GlcNAc)2 (94.8%), which make it a good candidate for the green recycling of chitinous waste. rChit46 could also significantly inhibit growth of the phytopathogenic fungus Botrytis cinerea, which endowed it with the potential as a biocontrol agent.

Improved antifungal activity of barley derived chitinase I gene that overexpress a 32 kDa recombinant chitinase in Escherichia coli host

Abstract Agricultural crops suffer many diseases, including fungal and bacterial infections, causing significant yield losses. The identification and characterisation of pathogenesis-related protein genes, such as chitinases, can lead to reduction in pathogen growth, thereby increasing tolerance against fungal pathogens. In the present study, the chitinase I gene was isolated from the genomic DNA of Barley (Hordeum vulgare L.) cultivar, Haider-93. The isolated DNA was used as template for the amplification of the ∼935 bp full-length chitinase I gene. Based on the sequence of the amplified gene fragment, class I barley chitinase shares 93% amino acid sequence homology with class II wheat chitinase. Interestingly, barley class I chitinase and class II chitinase do not share sequence homology. Furthermore, the amplified fragment was expressed in Escherichia coli Rosetta strain under the control of T7 promoter in pET 30a vector. Recombinant chitinase protein of 35 kDa exhibited highest expression at 0.5 mM concentration of IPTG. Expressed recombinant protein of 35 kDa was purified to homogeneity with affinity chromatography. Following purification, a Western blot assay for recombinant chitinase protein measuring 35 kDa was developed with His-tag specific antibodies. The purified recombinant chitinase protein was demonstrated to inhibit significantly the important phytopathogenic fungi Alternaria solani, Fusarium spp, Rhizoctonia solani and Verticillium dahliae compared to the control at concentrations of 80 µg and 200 µg.

Improved antifungal activity of barley derived chitinase I gene that overexpress a 32kDa recombinant chitinase in Escherichia coli host.

Agricultural crops suffer many diseases, including fungal and bacterial infections, causing significant yield losses. The identification and characterisation of pathogenesis-related protein genes, such as chitinases, can lead to reduction in pathogen growth, thereby increasing tolerance against fungal pathogens. In the present study, the chitinase I gene was isolated from the genomic DNA of Barley (Hordeum vulgare L.) cultivar, Haider-93. The isolated DNA was used as template for the amplification of the ∼935bp full-length chitinase I gene. Based on the sequence of the amplified gene fragment, class I barley chitinase shares 93% amino acid sequence homology with class II wheat chitinase. Interestingly, barley class I chitinase and class II chitinase do not share sequence homology. Furthermore, the amplified fragment was expressed in Escherichia coli Rosetta strain under the control of T7 promoter in pET 30a vector. Recombinant chitinase protein of 35kDa exhibited highest expression at 0.5mM concentration of IPTG. Expressed recombinant protein of 35kDa was purified to homogeneity with affinity chromatography. Following purification, a Western blot assay for recombinant chitinase protein measuring 35kDa was developed with His-tag specific antibodies. The purified recombinant chitinase protein was demonstrated to inhibit significantly the important phytopathogenic fungi Alternaria solani, Fusarium spp, Rhizoctonia solani and Verticillium dahliae compared to the control at concentrations of 80µg and 200µg.

Optimizing the expression of a Heterologous chitinase: A study of different promoters.

Many relevant applications have been demonstrated for chitinolytic enzymes. However, their successful exploitation depends upon the availability of strains and expression conditions that allow the production of active forms and large quantities of these enzymes. Escherichia coli has been commonly used to express and overproduce different proteins, among them chitinases. Improving the functional gene expression of chitinases is key to exploiting their potential. In a recent study, we described the effect of various parameters on the functional expression of 2 chitinases from different families, demonstrating that the effect of each of these parameters on the activity of both chitinases was specific to each enzyme. In this study, the expression of a Lactococcus lactis chitinase encoded by a new allele, ChiA1-2, was optimized. The results showed that not only the expression parameters seemed to influence protein production, solubility and activity but also the plasmid used for the expression. Herein, we describe the effect of 2 different promoters, tac and T7, on the expression of the active form of the chitinolytic enzyme.

Immobilization of a thermostable, fungal recombinant chitinase on biocompatible chitosan beads and the properties of the immobilized enzyme.

A recombinant, thermostable fungal chitinase from the thermophilic fungus, Thermomyces lanuginosus, was immobilized on glutaraldehyde cross-linked chitosan beads, and the properties of the immobilized chitinase were studied. The enzyme was found to be almost completely immobilized in 6 H under shaking condition at 30 °C. The immobilized enzyme exhibited much wider pH optimum and was more stable at alkaline pH values as compared with the soluble enzyme. Both the forms of the enzyme were optimally active at 60 °C and stable at 50 °C for 3 H, and after 3 H, the activity of the soluble enzyme declined sharply, whereas the immobilized chitinase was stable up to 6 H without any significant loss in the activity. KM and Vmax values of the immobilized enzyme were 1.18 mM and 445.7 µmol/Min/mg of protein, respectively. The immobilized enzyme was stable at least for 1 month at 4 °C without any significant loss in the activity.

A novel method for the immobilization of a thermostable fungal chitinase and the properties of the immobilized enzyme.

The recombinant thermostable fungal chitinase of Thermomyces lanuginosus was immobilized on the phenyl Sepharose matrix, and the properties of the immobilized chitinase were studied. The immobilized enzyme was optimally active at pH 6.0 and 50 °C and showed improved activity in the acidic range of pH values when compared with the soluble enzyme. The recombinant thermostable immobilized enzyme showed remarkable thermostability at 50 °C by retaining about 45% of the activity for more than 6 H. The KM and Vmax values were 1.3 mM and 4.5 mol/min/mg of protein, respectively. Both the free and immobilized forms of the enzymes were inhibited significantly by Ag(+) but behaved similarly to various other metal ions, detergents, and additives. The immobilized enzyme was stable for at least 1 month at 4 °C.

Cloning, characterization and expression of the chitinase gene of Enterobacter sp. NRG4.

A chitinase producing bacterium Enterobacter sp. NRG4, previously isolated in our laboratory, has been reported to have a wide range of applications such as anti-fungal activity, generation of fungal protoplasts and production of chitobiose and N-acetyl D-glucosamine from swollen chitin. In this paper, the gene coding for Enterobacter chitinase has been cloned and expressed in Escherichia coli BL21(DE3). The structural portion of the chitinase gene comprised of 1686 bp. The deduced amino acid sequence of chitinase has high degree of homology (99.0%) with chitinase from Serratia marcescens. The recombinant chitinase was purified to near homogeneity using His-Tag affinity chromatography. The purified recombinant chitinase had a specific activity of 2041.6 U mg(-1). It exhibited similar properties pH and temperature optima of 5.5 and 45°C respectively as that of native chitinase. Using swollen chitin as a substrate, the K(m), k(cat) and catalytic efficiency (k(cat)/K(m)) values of recombinant chitinase were found to be 1.27 mg ml(-1), 0.69 s(-1) and 0.54 s(-1)M(-1) respectively. Like native chitinase, the recombinant chitinase produced medicinally important N-acetyl D-glucosamine and chitobiose from swollen chitin and also inhibited the growth of many fungi.