Characterization of a chitinolytic enzyme from Serratia sp. KCK isolated from kimchi juice

Insights into Chitin-Degradation Potential of Shewanella khirikhana JW44 with Emphasis on Characterization and Function of a Chitinase Gene SkChi65

Chitin, a polymer of β-1,4-linked N-acetylglucosamine (GlcNAc), can be degraded into valuable oligosaccharides by various chitinases. In this study, the genome of Shewanella khirikhana JW44, displaying remarkable chitinolytic activity, was investigated to understand its chitin-degradation potential. A chitinase gene SkChi65 from this strain was then cloned, expressed, and purified to characterize its enzymatic properties and substrate hydrolysis. Genome analysis showed that, of the 14 genes related to chitin utilization in JW44, six belonged to glycoside hydrolase (GH) families because of their functional domains for chitin binding and catalysis. The recombinant chitinase SkChi65, consisting of 1129 amino acids, was identified as a member of the GH18 family and possessed two chitin-binding domains with a typical motif of [A/N]KWWT[N/S/Q] and one catalytic domain with motifs of DxxDxDxE, SxGG, YxR, and [E/D]xx[V/I]. SkChi65 was heterologously expressed as an active protein of 139.95 kDa best at 37 °C with 1.0 mM isopropyl-β-d-thiogalactopyranoside induction for 6 h. Purified SkChi65 displayed high stability over the ranges of 30-50 °C and pH 5.5-8.0 with optima at 40 °C and pH 7.0. The kinetic parameters Km, Vmax, and kcat of SkChi65 towards colloidal chitin were 27.2 μM, 299.2 μMs-1, and 10,203 s-1, respectively. In addition to colloidal chitin, SkChi65 showed high activity towards glycol chitosan and crystalline chitin. After analysis by thin-layer chromatography, the main products were N,N'-diacetylchitobiose, and GlcNAc with (GlcNAc)2-6 used as substrates. Collectively, SkChi65 could exhibit both exo- and endochitinase activities towards diverse substrates, and strain JW44 has a high potential for industrial application with an excellent capacity for chitin bioconversion.

Purification and characterization of Stenotrophomonas maltophilia chitinase with antifungal and insecticidal properties

This study aimed to determine the ability of bacteria to produce the chitinase enzyme, purify, and characterize the enzyme from the isolate with the best activity, and determine the use of this purified enzyme as a biocontrol agent. The chitinolytic bacterium was identified as Stenotrophomonas maltophilia. The chitinase enzyme was purified 1.4 times at a 30% ammonium sulfate concentration with a yield of 40.7%. Following partial purification, the enzyme was purified by ion-exchange chromatography using HiPrep Q XL 16/10 column and HiPrep™ 26/10 desalting column with 25.34% and 18.12% yields, respectively. It was calculated that the purified enzyme had a molecular weight of 52 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum activity of the enzyme was determined at 50 °C and pH 7.0. Enzyme activity was most induced by Fe²⁺, while it was most inhibited by Zn²⁺ at 5 mM concentration. K_m and V_max values of the enzyme for colloidal chitin were calculated as 1.6419 mg/mL and 16.129 U/mg, respectively. The purified chitinase was used as a biocontrol agent against the fungus Fusarium oxysporum and potato beetle Leptinotarsa decemlineata. The enzyme was shown to be effective in reducing the growth of fungus and causing disruption of the chitin structure of potato beetle.

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.

Mining and characterization of two novel chitinases from Hirsutella sinensis using an efficient transcriptome-mining approach

Two novel family 18 chitinases, chiA and chiH, were identified and cloned from the transcriptome of H. sinensis based on the transcriptome sequence data. The recombinant chitinases were overexpressed in Escherichia coli BL21, subsequently purified and functionally characterized. The optimal temperature and pH for chiA were 55 °C and 5.0, respectively, and those for chiH were 50 °C and 5.0, respectively. The highest enzyme activities of 11.5 U/mg and 8.1 U/mg were obtained for chiA and chiH, respectively, when colloidal chitin was used as the substrate with Ba²⁺. chiA exhibited higher V_max of 1.94 μmol/μg/h and k_cat of 1.443 S^-1 than those of chiH with V_max of 1.63 μmol/μg/h and k_cat of 1.175 S^-1, and both were efficient towards colloidal chitin compared with other typical family 18 chitinases. Substrate specificity and gene expression analyses indicated that chiA and chiH preferred substrates containing N-acetyl groups, such as colloidal chitin and glycol chitin, while no activity was detected toward laminarin, cellobiose, carboxymethyl cellulose and starch. The work presented here would aid in the understanding and performance of future studies on the infection mechanism of H. sinensis.

Optimized production of Serratia marcescens B742 mutants for preparing chitin from shrimp shells powders

To improve the deproteinization (DP) efficacy of shrimp shell powders (SSP) for preparing chitin, Serratia marcescens B742 mutants were prepared using 2% diethyl sulfate (DES), UV-irradiation, and/or microwave heating treatments. Both single-stage and multi-stage mutations were investigated for optimizing S. marcescens B742 mutation conditions. Under the optimized mutation conditions (2% DES treatment for 30min plus successive 20min UV-irradiation), the protease and chitosanase activity produced by mutant S. marcescens B742 was 240.15 and 170.6mU/mL, respectively, as compared with 212.58±1.51 and 83.75±6.51mU/mL, respectively, by wild S. marcescens B742. DP efficacy of SSP by mutant S. marcescens B742 reached 91.4±4.6% after 3d of submerged fermentation instead of 83.4±4.7% from the wild S. marcescens B742 after 4d of submerged fermentation. Molecular mass of chitosanase and protease was 41.20 and 47.10kDa, respectively, and both enzymes were verified by mass spectrometry analysis. The chitosanase from both wild and mutant S. marcescens B742 was activated by sodium dodecyl sulfate (SDS), Tween 20, Tween 40, and Triton-100, and the protease and chitosanase were strongly inhibited by ethylenediaminetetraacetic acid (EDTA). These results suggested that S. marcescens B742 mutants can be used in the biological production of chitin through deproteinization of SSP.

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.

Production of a Thermostable and Alkaline Chitinase by Bacillus thuringiensis subsp. kurstaki Strain HBK-51

This paper reports the isolation and identification of chitinase-producing Bacillus from chitin-containing wastes, production of a thermostable and alkaline chitinasese, and enzyme characterization. Bacillus thuringiensis subsp. kurstaki HBK-51 was isolated from soil and was identified. Chitinase was obtained from supernatant of B. thuringiensis HBK-51 strain and showed its optimum activity at 110°C and at pH 9.0. Following 3 hours of incubation period, the enzyme showed a high level of activity at 110°C (96% remaining activity) and between pH 9.0 and 12.0 (98% remaining activity). Considering these characteristics, the enzyme was described as hyperthermophile-thermostable and highly alkaline. Two bands of the enzyme weighing 50 and 125 kDa were obtained following 12% SDS-PAGE analyses. Among the metal ions and chemicals used, Ni(2+) (32%), K(+) (44%), and Cu(2+) (56%) increased the enzyme activity while EDTA (7%), SDS (7%), Hg(2+) (11%), and ethyl-acetimidate (20%) decreased the activity of the enzyme. Bacillus thuringiensis subsp. kurstaki HBK-51 is an important strain which can be used in several biotechnological applications as a chitinase producer.

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.

Performance and molecular evaluation of an anaerobic system with suspended biomass for treating wastewater with high fat content after enzymatic hydrolysis

The effect of a lipase-rich fungal enzymatic preparation, produced by a Penicillium sp. during solid-state fermentation, was evaluated in an anaerobic digester treating dairy wastewater with 1200 mg of oil and grease/L. The oil and grease hydrolysis step was carried out with 0.1% (w/v) of solid enzymatic preparation at 30 degrees C for 24 h, and resulted in a final free acid concentration eight times higher than the initial value. The digester operated in sequential batches of 48 h at 30 degrees C for 245 days, and had high chemical oxygen demand (COD) removal efficiencies (around 90%) when fed with pre-hydrolyzed wastewater. However, when the pre-hydrolysis step was removed, the anaerobic digester performed poorly (with an average COD removal of 32%), as the oil and grease accumulated in the biomass and effluent oil and grease concentration increased throughout the operational period. PCR-DGGE analysis of the Bacteria and Archaea domains revealed remarkable differences in the microbial profiles in trials conducted with and without the pre-hydrolysis step, indicating that differences observed in overall parameters were intrinsically related to the microbial diversity of the anaerobic sludge.

Conversion of squid pen by Serratia ureilytica for the production of enzymes and antioxidants

Two proteases (P1 and P2) and a chitinase (C1) were purified from the culture supernatant of Serratia ureilytica TKU013 with squid pen as the sole carbon/nitrogen source. The molecular masses of P1, P2 and C1 determined by SDS-PAGE were approximately 50 kDa, 50 kDa and 60 kDa, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of P1, P2 and C1 were (pH 10, 40 degrees C, pH 7-11, and <50 degrees C), (pH 10, 40 degrees C, pH 8-11, and <40 degrees C) and (pH 6, 50 degrees C, pH 5-8, and <50 degrees C), respectively. P1 and P2 were inhibited by Mg(2+), EDTA and C1 was inhibited completely by Cu(2+). The antioxidant activity of TKU013 culture supernatant was 72% per mL (DPPH scavenging ability). With this method, we have shown that squid pen wastes can be utilized and have revealed its hidden potential in the production of functional foods.

Chitinolytic activities of Clostridium sp. JM2 isolated from stool of human administered per orally by chitosan

The novel chitinolytic bacterium Clostridium beijerinckii strain JM2 was isolated from the stool of healthy volunteers supplied daily per orally with 3 g of chitosan. The bacterium grown on colloidal chitin produced a complete array of chitinolytic enzymes. Significant activities of endochitinase, exochitinase and chitosanase were excreted into the medium (301, 282 and 268 nkat/microg protein, respectively). The high cellular activity of N-acetyl-beta-glucosaminidase (NAGase) and chitosanase were detected (732.4 and 154 nkat/microg protein, respectively). NAGase activity represented the main activity associated with the cellular fraction. The activities of both enzymes tested increased from 20 to 50 degrees C; the optimum reaction temperature estimated being 50 degrees C. Endochitinase as well as NAGase showed an activity in the pH interval of 4.0-8.0; the optimum pH values were 6.5 and 6.0, respectively. The extracellular endochitinase complex consisted of six isoenzymes with molar mass of 32-76 kDa; in the cellular fraction five bands with molar mass of 45-86 kDa were detected. Exochitinase activity was demonstrated in the form of three bands (with molar mass of 30-57 kDa), NAGase activity displayed one band of 45 kDa.

Characterization and role of a metalloprotease induced by chitin in Serratia sp. KCK

A metalloprotease induced by chitin in a new chitinolytic bacterium Serratia sp. Strain KCK was purified and characterized. Compared with other Serratia enzymes, it exhibited a rather broad pH activity range (pH 5.0-8.0), and thermostability. The cognate ORF, mpr, was cloned and expressed. Its deduced amino acid sequence showed high similarity to those of bacterial zinc-binding metalloproteases and a well-conserved serralysin family motif. Pretreatment of chitin with the Mpr protein promoted chitin degradation by chitinase A, which suggests that Mpr participates in, and facilitates, chitin degradation by this microorganism.