Chitooligosaccharides enzymatic production by Metarhizium anisopliae

Cloning and Characterization of Chitin Deacetylase from Euphausia superba

Chitin deacetylase (CDA) can catalyze the deacetylation of chitin to produce chitosan. In this study, we identified and characterized a chitin deacetylase gene from Euphausia superba (EsCDA-9k), and a soluble recombinant protein chitin deacetylase from Euphausia superba of molecular weight 45 kDa was cloned, expressed, and purified. The full-length cDNA sequence of EsCDA-9k was 1068 bp long and encoded 355 amino acid residues that contained the typical domain structure of carbohydrate esterase family 4. The predicted three-dimensional structure of EsCDA-9k showed a 67.32% homology with Penaeus monodon. Recombinant chitin deacetylase had the highest activity at 40 °C and pH 8.0 in Tris-HCl buffer. The enzyme activity was enhanced by metal ions Co2+, Fe3+, Ca2+, and Na+, while it was inhibited by Zn2+, Ba2+, Mg2+, and EDTA. Molecular simulation of EsCDA-9k was conducted based on sequence alignment and homology modeling. The EsCDA-9k F18G mutant showed a 1.6-fold higher activity than the wild-type enzyme. In summary, this is the first report of the cloning and heterologous expression of the chitin deacetylase gene in Euphausia superba. The characterization and function study of EsCDA-9k will serve as an important reference point for future application.

Expression and Molecular Modification of Chitin Deacetylase from Streptomyces bacillaris

Chitin deacetylase can be used in the green and efficient preparation of chitosan from chitin. Herein, a novel chitin deacetylase SbCDA from Streptomyces bacillaris was heterologously expressed and comprehensively characterized. SbDNA exhibits its highest deacetylation activity at 35 °C and pH 8.0. The enzyme activity is enhanced by Mn²⁺ and prominently inhibited by Zn²⁺, SDS, and EDTA. SbCDA showed better deacetylation activity on colloidal chitin, (GlcNAc)₅, and (GlcNAc)₆ than other forms of the substrate. Molecular modification of SbCDA was conducted based on sequence alignment and homology modeling. A mutant SbCDA63G with higher activity and better temperature stability was obtained. The deacetylation activity of SbCDA63G was increased by 133% compared with the original enzyme, and the optimal reaction temperature increased from 35 to 40 °C. The half-life of SbCDA63G at 40 °C is 15 h, which was 5 h longer than that of the original enzyme. The improved characteristics of the chitin deacetylase SbCDA63G make it a potential candidate to industrially produce chitosan from chitin.

Marginal lands and fungi - linking the type of soil contamination with fungal community composition

Fungi can be found in almost all ecosystems. Some of them can even survive in harsh, anthropogenically transformed environments, such as post-industrial soils. In order to verify how the soil fungal diversity may be changed by pollution, two soil samples from each of the 28 post-industrial sites were collected. Each soil sample was characterized in terms of concentration of heavy metals and petroleum derivatives. To identify soil fungal communities, fungal ITS2 amplicon was sequenced for each sample using Illumina MiSeq platform. There were significant differences in the community structure and taxonomic diversity among the analyzed samples. The highest taxon richness and evenness were observed in the non-polluted sites, and lower numbers of taxa were identified in multi-polluted soils. The presence of monocyclic aromatic hydrocarbons, gasoline, and mineral oil were determined as the factors driving the differences in the mycobiome. Further, in the culture-based selection experiment, two main groups of fungi growing on polluted media were identified - generalists able to live in the presence of pollution, and specialists adapted to the usage of BTEX as a sole source of energy. Our selection experiment proved that it is long-term soil contamination that shapes the community, rather than temporary addition of pollutant. This article is protected by copyright. All rights reserved.

Inhibition of Liver Tumor Cell Metastasis by Partially Acetylated Chitosan Oligosaccharide on A Tumor-Vessel Microsystem

Chitooligosaccharides (COS), the only cationic oligosaccharide in nature, have been demonstrated to have anti-tumor activity. However, the inhibitory effects of COS on different stages of tumor metastasis are still unknown, and it is not clear what stage(s) of tumor metastasis COS targeted. To study the inhibitory effects of a new partially acetylated chitooligosaccharide (paCOS) with fraction of acetylation (FA) 0.46 on each phase of liver cancer cell metastasis, a dynamic tumor-vessel microsystem undergoing physiological flow was leveraged. paCOS (FA = 0.46) significantly inhibited proliferation of HepG2 cells through vascular absorption on the chip, and inhibited migration of HepG2 cells by inhibiting the formation of pseudopod in liver tumor cells. It was also found that paCOS at 10 μg/mL had a stronger inhibitory effect on liver tumor cells invading blood vessels than that of paCOS at 100 μg/mL, and paCOS at 100 μg/mL, which had a significant destructive effect on tumor vascular growth and barrier function. Moreover, paCOS reduced the number of liver tumor cells adhering onto the surface of HUVECs layer after 3 h of treatment. Therefore, the results revealed that paCOS had considerable potential as drugs for anti-tumor metastasis.

Identification of an endo-chitinase from Corallococcus sp. EGB and evaluation of its antifungal properties

As the main component of the fungal cell wall, chitin has been regarded as an optimal molecular target for the biocontrol of plant-pathogenic fungi. In this study, the chitin hydrolase CcCti1, which belongs to the glycoside hydrolase family 18 (GH 18) and exhibits potential antifungal activity, was identified from Corallococcus sp. EGB. CcCti1 lacks a fibronectin type-III (FN3) domain that is present in similar enzymes from most genera of myxobacteria, indicating that CcCti1 may have acquired chitinase activity due to the FN3 domain deletion during myxobacterial evolution. CcCti1 was expressed in Escherichia coli BL21 (DE3) with a specific activity of up to 10.5 U/μmol with colloidal chitin as the substrate. Product analysis showed that CcCti1 could hydrolyze chitin into N-acetylated chitohexaose (GlcNAc)₆ as the major product, in addition to chitooligosaccharides. The analysis of biochemical properties indicated that the CBD and FN3 domains in CcCti1 determine the substrate affinity and pH stability. Otherwise, CcCti1 exhibited efficient biocontrol activity against the plant pathogen Magnaporthe oryzae in a dose-dependent manner, inhibiting the conidia germination and appressoria formation at a concentration of 0.08 mg/mL. Overall, the chitohexaose-producing chitinase CcCti1 with hydrolytic features may find potential application in chitin conversion and biocontrol of fungal plant diseases.

Optimization of chitosanase production by Bacillus mojavensis EGE-B-5.2i

Maximum production of industrially important enzymes such as chitosanases through media optimization still holds foremost interest. The present study was conducted to improve chitosanase activity of an indigenous strain identified as Bacillus mojavensis. Initially, carbon and nitrogen sources were optimized by one-variable-at-a-time approach. Further, fermentation medium was optimized using Plackett-Burman (PB) and central composite designs (CCD). PB verified soluble starch (SS), colloidal chitosan (CC) peptone, and NaCl as most significant variables affecting chitosanase production. CCD results predicted the optimum concentrations of SS, CC, peptone, and NaCl as 7.8, 7.0, 6.5, and 2.7 g L^-1 , respectively to achieve maximum chitosanase activity (21.1 U ml^-1 ). Discovery of the novel optimal medium has improved chitosanase production by B. mojavensis up-to 9.5 folds. Lastly, 18.6 U ml^-1 chitosanase activity was achieved in stirred tank bioreactor using optimal medium, which is quite satisfactory to proclaim this strain as a potential candidate to provide commercial chitosanase.

Bioconversion of Chitin to Bioactive Chitooligosaccharides: Amelioration and Coastal Pollution Reduction by Microbial Resources

Chitin-metabolizing products are of high industrial relevance in current scenario due to their wide biological applications, relatively lower cost, greater abundance, and sustainable supply. Chitooligosaccharides have remarkably wide spectrum of applications in therapeutics such as antitumor agents, immunomodulators, drug delivery, gene therapy, wound dressings, as chitinase inhibitors to prevent malaria. Hypocholesterolemic and antimicrobial activities of chitooligosaccharides make them a molecule of choice for food industry, and their functional profile depends on the physicochemical characteristics. Recently, chitin-based nanomaterials are also gaining tremendous importance in biomedical and agricultural applications. Crystallinity and insolubility of chitin imposes a major hurdle in the way of polymer utilization. Chemical production processes are known to produce chitooligosaccharides with variable degree of polymerization and properties along with ecological concerns. Biological production routes mainly involve chitinases, chitosanases, and chitin-binding proteins. Development of bio-catalytic production routes for chitin will not only enhance the production of commercially viable chitooligosaccharides with defined molecular properties but will also provide a means to combat marine pollution with value addition.