Microbial chitinases and their relevance in various industries

Statement concerning the review of the approval of the basic substances chitosan and chitosan hydrochloride when used in plant protection

The European Commission asked EFSA to provide an opinion according to Article 23(6) of Regulation (EC) No 1107/2009, in conjunction with Article 29 of Regulation (EC) No 178/2002, regarding the approved plant protection uses of chitosan and chitosan hydrochloride as basic substances. The Panel on Plant Protection Products and their Residues (PPR) was not provided with new dossiers but collated available scientific and technical knowledge and used a weight of evidence approach and experts' judgement for its appraisal. The statement has considered the possibility for extrapolation of the toxicological properties between chitosan and chitosan hydrochloride, and whether both substances can be expected to be of no toxicological concern; a comparison between the estimated levels of chitosan and chitosan hydrochloride resulting from the approved uses as basic substances and the level of chitosan expected to naturally occur in the environment. This last comparison served to verify whether the approved uses as basic substances might lead to an exceedance of the expected natural background levels in any of the environmental compartments (quantitative for the soil compartment and (semi)quantitative for the freshwater compartment); and accordingly, whether there was a need to advise on the safety of chitosan and chitosan hydrochloride to non-target species occurring in the impacted environmental compartments. Overall, the PPR Panel concluded that toxicological properties can be extrapolated between chitosan and chitosan hydrochloride and that no toxicological concerns were identified. The estimated levels of chitosan and chitosan hydrochloride in the environment following application in accordance with their approved uses as basic substances would be within the same range, or below, the expected natural background exposure levels in soil and freshwaters. Considering the available ecotoxicological data and the environmental fate assessment, further consideration in relation to the safety to non-target organisms was considered not necessary. Missing information alongside related uncertainties have been identified and considered in the overall weight of the evidence.

Biotransformation of agar extraction waste into cultivation matrix using an adaptively evolved Paenibacillus mucilaginosus strain

Industrial agar extraction waste (AEW), which consists of resistant K-rich perlite and agar-dominated seaweed residues, poses environmental challenges. In this study, we isolated K-solubilizing bacteria from an AEW storage yard and identified the adaptively evolved strain, ZK03-Aga1, with efficient K-solubilizing and agar-utilizing properties. Co-fermentation of ZK03-Aga1 with AEW significantly enhanced the production of oligosaccharides, K, and soluble solids. These products, combined with a commercial soilless matrix, form a composite matrix that has been validated for fertility through bok choy planting experiments. The results showed increased bok choy yield, energy, protein, trace element, and chlorophyll content. Bacterial community composition analysis indicated an increase in nitrogen-fixing and organic matter-degrading bacteria. This suggests that AEW nutrients, via ZK03-Aga1 fermentation, directly benefit crops, improving yield, quality, and microbial structure for sustainable fertility. This study presents an efficient method for reusing AEW and mitigating its environmental impacts.

Engineering Bacterial Chitinases for Industrial Application: From Protein Engineering to Bacterial Strains Mutation! A Comprehensive Review of Physical, Molecular, and Computational Approaches

Bacterial chitinases are integral in breaking down chitin, the natural polymer in crustacean and insect exoskeletons. Their increasing utilization across various sectors such as agriculture, waste management, biotechnology, food processing, and pharmaceutical industries highlights their significance as biocatalysts. The current review investigates various scientific strategies to maximize the efficiency and production of bacterial chitinases for industrial use. Our goal is to optimize the heterologous production process using physical, molecular, and computational tools. Physical methods focus on isolating, purifying, and characterizing chitinases from various sources to ensure optimal conditions for maximum enzyme activity. Molecular techniques involve gene cloning, site-directed mutation, and CRISPR-Cas9 gene editing as an approach for creating chitinases with improved catalytic activity, substrate specificity, and stability. Computational approaches use molecular modeling, docking, and simulation techniques to accurately predict enzyme-substrate interactions and enhance chitinase variants' design. Integrating multidisciplinary strategies enables the development of highly efficient chitinases tailored for specific industrial applications. This review summarizes current knowledge and advances in chitinase engineering to serve as an indispensable guideline for researchers and industrialists seeking to optimize chitinase production for various uses.

Chitinases: expanding the boundaries of knowledge beyond routinized chitin degradation

Chitinases, enzymes that degrade chitin, have long been studied for their role in various biological processes. They play crucial roles in the moulting process of invertebrates, the digestion of chitinous food, and defense against chitin-bearing pathogens. Additionally, chitinases are involved in physiological functions in crustaceans, such as chitinous food digestion, moulting, and stress response. Moreover, chitinases are universally distributed in organisms from viruses to mammals and have diverse functions including tissue degradation and remodeling, nutrition uptake, pathogen invasion, and immune response regulation. The discovery of these diverse functions expands our understanding of the biological significance and potential applications of chitinases. However, recent research has shown that chitinases possess several other functions beyond just chitin degradation. Their potential as biopesticides, therapeutic agents, and tools for bioremediation underscores their significance in addressing global challenges. More importantly, we noted that they may be applied as bioweapons if ethical regulations regarding production, engineering and application are overlooked.

Surface defects due to bacterial residue on shrimp shell

The changes in the surface chemistry and morphological structure of chitin forms obtained from shrimp shells (ShpS) with and without microorganisms were evaluated. Total mesophilic aerobic bacteria (TMAB), estimated Pseudomonas spp. and Enterococcus spp. were counted in Shp-S by classical cultural counting on agar medium, where the counts were 6.56 ± 0.09, 6.30 ± 0.12, and 3.15 ± 0.03 CFU/g, respectively. Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM)/Energy dispersed X-ray (EDX) were used to assess the surface chemistry/functional groups and morphological structure for ChTfree (non-microorganism), and ChTmo (with microorganisms). ChTfree FTIR spectra presented a detailed chitin structure by OH, NH, and CO stretching vibrations, whereas specific peaks of chitin could not be detected in ChTmo. Major differences were also found in SEM analysis for ChTfree and ChTmo. ChTfree had a flat, prominent micropore, partially homogeneous structure, while ChTmo had a layered, heterogeneous, complex dense fibrous, and lost pores form. The degree of deacetylation was calculated for ChTfree and ChTmo according to FTIR and EDX data. The results suggest that the degree of deacetylation decreases in the presence of microorganisms, affecting the production of beneficial components negatively. The findings were also supported by the molecular docking model.

Alternative splicing of chitin deacetylase 2 regulates chitin and fatty acid metabolism in Asian citrus psyllid, Diaphorina citri

Chitin plays an important role in the development and molting of insects. The key genes involved in chitin metabolism were considered promising targets for pest control. In this study, two splice variants of chitin deacetylase 2 (CDA2) from Diaphorina citri were identified, including DcCDA2a and DcCDA2b. Bioinformatics analysis revealed that DcCDA2a and DcCDA2b encoded 550 and 544 amino acid residues with a signal peptide, respectively. Spatio-temporal expression patterns analysis showed that DcCDA2a and DcCDA2b were highly expressed in D. citri wing and nymph stages. Moreover, DcCDA2a and DcCDA2b expression levels were induced by 20-hydroxyecdysone (20E). Silencing DcCDA2a by RNA interference (RNAi) significantly disrupted the D. citri molting and increased D. citri mortality and malformation rate, whereas inhibition of DcCDA2b resulted in a semimolting phenotype. Furthermore, silencing DcCDA2a and DcCDA2b significantly suppressed D. citri chitin and fatty acid metabolism. Our results indicated that DcCDA2 might play crucial roles in regulating D. citri chitin and fatty acid metabolism, and it could be used as a potential target for controlling D. citri.

An overview of fungal chitinases and their potential applications

Chitin, the world's second most abundant biopolymer after cellulose, is composed of β-1,4-N-acetylglucosamine (GlcNAc) residues. It is the key structural component of many organisms, including crustaceans, mollusks, marine invertebrates, algae, fungi, insects, and nematodes. There has been a significant increase in the generation of chitinous waste from seafood businesses, resulting in a big amount of scrap. Although several organisms, such as plants, crustaceans, insects, nematodes, and animals, produce chitinases, microorganisms are promising candidates and a sustainable option that mediates chitin degradation. Fungi are the dominant group of chitinase producers among microorganisms. In fungi, chitinases are involved in morphogenesis, cell division, autolysis, chitin acquisition for nutritional purposes, and mycoparasitism. Many efficient chitinolytic fungi with potential applications have been identified in a variety of environments, including soil, water, marine wastes, and plants. The current review highlights the key sources of chitinolytic fungi and the characterization of fungal chitinases. It also discusses the applications of fungal chitinases and the cloning of fungal chitinase genes.