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

Sclerotia degradation by Trichoderma-mycoparasitic; an effective and sustainable trend in the drop lettuce disease control caused by Sclerotinia sclerotiorum

Controlling the hazard of sclerotia produced by the Sclerotinia sclerotiorum is very complex, and it is urgent to adopt an effective method that is harmonious environmentally to control the disease. Among the six isolates isolated from the rhizosphere of lettuce, the isolate HZA84 demonstrated a high activity in its antagonism towards Sclerotinia sclerotiorum in vitro, and produces siderophore. By amplification of internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF1-α), and RNA polymerase II subunit (RPB2) genes, the isolate HZA84 was identified as Trichoderma asperellum, which was confirmed by analysis of phylogenetic tree. The Scanning electron microscope monitoring detected that the isolate HZA84 spread over the sclerotial surface, thus, damaging, decomposing, and distorting the globular cells of the outer cortex of the sclerotia. The Real-time polymerase chain reaction (RT-qPCR) analysis disclosed the overexpression of two genes (chit33 and chit37) encoding the endochitinase in addition to one gene (prb1) encoding the proteinase during 4 and 8 days of the parasitism behavior of isolate HZA84 on the sclerotia surface. These enzymes aligned together in the sclerotia destruction by hyperparasitism. On the other hand, the pots trial revealed that spraying of isolate HZA84 reduced the drop disease symptoms of lettuce. The disease severity was decreased by 19.33 and the biocontrol efficiency was increased by 80.67% within the fourth week of inoculation. These findings magnify the unique role of Trichoderma in disrupting the development of plant diseases in sustainable ways.

Response surface optimization, purification, characterization and short-chain chitooligosaccharides production from an acidic, thermostable chitinase from Thermomyces dupontii

Chitin, recovered in huge amounts from coastal waste, may biocatalytically valorized for utilization in food and biotech sectors. Conventional chemical-based conversion makes use of significant volumes of hazardous acid and alkali. Alternatively, enzymes offer better process control and generation of homogeneous products. Process variables were derived to achieve augmented levels of chitinase (3.8809 Ul-1 h-1) productivity from a novel thermophilic fungal strain Thermomyces dupontii, ITCC 9104 following incubation (96 h, 45 °C). An acidic thermostable chitinase TdChiT having molecular mass of 60 kDa has been purified. Optimal TdChiT activity has been demonstrated at 70 °C and pH 5. Notably decreased activity over a broad range of temperature and pH was observed following deglycosylation. Half-life, activation energy, Gibbs free energy, enthalpy and entropy for denaturation of TdChiT at its optimum temperature were 197.40 min, 105.48 kJ mol-1, 100.59 kJ mol-1, 102.64 kJ mol-1 and 5.95 J mol-1 K-1. TdChiT has specificity towards colloidal chitin and (GlcNAc)2-4. Metal ions viz. Mn2+, Ca2+ and Co2+ and nonionic surfactants notably enhanced chitinase activity. Thin layer chromatography analysis has revealed effective hydrolysis of colloidal chitin and (GlcNAc)2-4. TdChiT may potentially be employed for design of better, eco-friendly and less resource-intensive industrial procedures for upcycling of crustacean waste into value-added organonitrogens.

Boosting one-step degradation of shrimp shell waste to produce chitin oligosaccharides at smart nanoscale enzyme reactor with liquid-solid system

Chitin oligosaccharides (CTOS) possess potential applications in food, medicine, and agriculture. However, lower mass transfer and catalytic efficiency are the main kinetic limitations for the production of CTOS from shrimp shell waste (SSW) and crystalline chitin. Chemical or physical methods are usually used for pretreatment to improve chitinase hydrolysis efficiency, but this is not eco-friendly and cost-effective. To address this challenge, a chitinase nanoreactor with the liquid-solid system (BcChiA1@ZIF-8) was manufactured to boost the one-step degradation of SSW and crystalline chitin. Compared with free enzyme, the catalytic efficiency of BcChiA1@ZIF-8 on colloidal chitin was significantly improved to 142 %. SSW and crystalline chitin can be directly degraded by BcChiA1@ZIF-8 without any pretreatments. The yield of N, N'-diacetylchitobiose [(GlcNAc)2] from SSW and N-acetyl-D-glucosamine (GlcNAc) from crystalline chitin was 2 times and 3.1 times than that of free enzyme, respectively. The reason was that BcChiA1@ZIF-8 with a liquid-solid system enlarged the interface area, increased the collision frequency between enzyme and substrate, and improved the large-substrates binding activity of chitinase. Moreover, the biphasic system exhibited excellent stability, and the design showed universal applicability. This strategy provided novel guidance for other polysaccharide biosynthesis and the conversion of environmental waste into carbohydrates.

Expression profiles and characterization of microRNAs responding to chitin in Arthrobotrys oligospora

Extracellular proteases, such as chitinases secreted by Arthrobotrys oligospora (A. oligospora), play a crucial role in the process of nematode infection. However, post-transcriptional regulation of gene expression involving microRNAs (miRNAs) in A. oligospora remains scarcely described. Hereto, transcriptome sequencing was carried out to analyze the expression profiles of chitin-responsive miRNAs in A. oligospora. Based on the RNA-seq data, the differential expression of miRNAs (DEmiRNAs) in response to chitin was screened, identified and characterized in A. oligospora. Meanwhile, the potential target genes were predicted by the online tools miRanda and Targetscan, respectively. Furthermore, the interaction of DEmiRNA with it's target gene was validated by a dual-luciferase reporter assay system. Among 85 novel miRNAs identified, 25 miRNAs displayed significant differences in expression in A. oligospora in response to chitin. Gene Ontology (GO) analysis showed that the potential genes targeted by DEmiRNAs were enriched in the biological processes such as bio-degradation, extracellular components and cell cycle. KEGG analysis revealed that the target genes were mainly involved in Hippo, carbon and riboflavin metabolic pathway. Outstandingly, chitinase AOL_s00004g379, which is involved in the hydrolysis metabolic pathway of chitin, was confirmed to be a target gene of differential miR_70. These findings suggest that chitin-responsive miRNAs are involved in the regulation of cell proliferation, predator hyphae growth and chitinase expression through the mechanisms of post-transcriptional regulation, which provides a new perspective to the molecular mechanisms underlying miRNAs-mediated control of gene expression in A. oligospora.

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.

Development of a two-enzyme system in Aspergillus niger for efficient production of N-acetyl-β-D-glucosamine from powdery chitin

A chitinase (PbChi70) from Paenibacillus barengoltzii was engineered by directed evolution to enhance its hydrolysis efficiency towards powder chitin. Through two rounds of screening, a mutant (mPbChi70) with a maximum specific activity of 73.21 U/mg was obtained, which is by far the highest value ever reported. The mutant gene was further transformed into Aspergillus niger FBL-B (ΔglaA) which could secrete high level of endogenously β-N-acetylglucosaminidase (GlcNAcase), thus a two-enzyme expression system was constructed. The highest chitinase activity of 61.33 U/mL with GlcNAcase activity of 353.1 U/mL was obtained in a 5-L fermentor by high-cell density fermentation. The chitin-degrading enzyme cocktail was used for the bioconversion of GlcNAc from powder chitin directly, and the highest conversion ratio reached high up to 71.9 % (w/w) with GlcNAc purity ≥95 % (w/w). This study may provide an excellent chitinase as well as a double enzyme cocktail system for efficient biological conversion of chitin materials.

Candida albicans chitinase 3 with potential as a vaccine antigen: production, purification, and characterisation

Chitinases are widely studied enzymes that have already found widespread application. Their continued development and valorisation will be driven by the identification of new and improved variants and/or novel applications bringing benefits to industry and society. We previously identified a novel application for chitinases wherein the Candida albicans cell wall surface chitinase 3 (Cht3) was shown to have potential in vaccine applications as a subunit antigen against fungal infections. In the present study, this enzyme was investigated further, developing production and purification protocols, enriching our understanding of its properties, and advancing its application potential. Cht3 was heterologously expressed in Pichia pastoris and a 4-step purification protocol developed and optimised: this involves activated carbon treatment, hydrophobic interaction chromatography, ammonium sulphate precipitation, and gel filtration chromatography. The recombinant enzyme was shown to be mainly O-glycosylated and to retain the epitopes of the native protein. Functional studies showed it to be highly specific, displaying activity on chitin, chitosan, and chito-oligosaccharides larger than chitotriose only. Furthermore, it was shown to be a stable enzyme, exhibiting activity, and stability over broad pH and temperature ranges. This study represents an important step forward in our understanding of Cht3 and contributes to its development for application.

N-acetyl-d-glucosamine-based oligosaccharides from chitin: Enzymatic production, characterization and biological activities

Chitin, the second most abundant biopolymer, possesses diverse applications in the food, agricultural, and pharmaceutical industries due to its functional properties. However, the potential applications of chitin are limited owing to its high crystallinity and low solubility. N-acetyl chitooligosaccharides and lacto-N-triose II, the two types of GlcNAc-based oligosaccharides, can be obtained from chitin by enzymatic methods. With their lower molecular weights and improved solubility, these two types of GlcNAc-based oligosaccharides display more various beneficial health effects when compared to chitin. Among their abilities, they have exhibited antioxidant, anti-inflammatory, anti-tumor, antimicrobial, and plant elicitor activities as well as immunomodulatory and prebiotic effects, which suggests they have the potential to be utilized as food additives, functional daily supplements, drug precursors, elicitors for plants, and prebiotics. This review comprehensively covers the enzymatic methods used for the two types of GlcNAc-based oligosaccharides production from chitin by chitinolytic enzymes. Moreover, current advances in the structural characterization and biological activities of these two types of GlcNAc-based oligosaccharides are summarized in the review. We also highlight current problems in the production of these oligosaccharides and trends in their development, aiming to offer some directions for producing functional oligosaccharides from chitin.

Fused expression of Sm1-Chit42 proteins for synergistic mycoparasitic response of Trichoderma afroharzianum on Botrytis cinerea

Sm1 and Chit42 of Trichoderma have been universally confirmed as crucial biocontrol factors against pathogen infection through induced resistance and mycoparasitism, respectively. However, not enough work has been conducted to understand the novel function of fused expression of these two proteins in Trichoderma. The results of this study demonstrated that Sm1-Chit42 protein (SCf) engineered T. afroharzianum strain OE:SCf exerted synergistic inhibition to Botrytis cinerea growth at multiple stages of mycoparasitic interaction of T. afroharzianum and B. cinerea including chemotropism sensing, hyphal coiling, hydrophobicity modulation, cell wall adhesion, virulence reduction and pathogen killing by ROS. These results highlight a novel mycoparasitic system in Trichoderma strains engineered with Sm1-Chit42 chimeric protein to combat B. cinerea growth and reproduction, which would lay a strong foundation for exploring a new engineered Trichoderma biofungicide created with chimeric proteins in the future.

Metal Nanomaterials and Hydrolytic Enzyme-Based Formulations for Improved Antifungal Activity

Active research of metal-containing compounds and enzymes as effective antifungal agents is currently being conducted due to the growing antifungal resistance problem. Metals are attracting special attention due to the wide variety of ligands that can be used for them, including chemically synthesized and naturally obtained variants as a result of the so-called "green synthesis". The main mechanism of the antifungal action of metals is the triggering of the generation and accumulation of reactive oxygen species (ROS). Further action of ROS on various biomolecules is nonspecific. Various hydrolytic enzymes (glucanases and proteases), in turn, exhibit antifungal properties by affecting the structural elements of fungal cells (cell walls, membranes), fungal quorum sensing molecules, fungal own protective agents (mycotoxins and antibiotics), and proteins responsible for the adhesion and formation of stable, highly concentrated populations in the form of biofilms. A wide substrate range of enzymes allows the use of various mechanisms of their antifungal actions. In this review, we discuss the prospects of combining two different types of antifungal agents (metals and enzymes) against mycelial fungi and yeast cells. Special attention is paid to the possible influence of metals on the activity of the enzymes and the possible effects of proteins on the antifungal activity of metal-containing compounds.

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.

Biochemical Properties of a Cold-Active Chitinase from Marine Trichoderma gamsii R1 and Its Application to Preparation of Chitin Oligosaccharides

The enzymatic degradation of different chitin polymers into chitin oligosaccharides (COSs) is of great significance given their better solubility and various biological applications. Chitinase plays a pivotal role in the enzymatic preparation of COSs. Herein, a cold-adapted and efficient chitinase (ChiTg) from the marine Trichoderma gamsii R1 was purified and characterized. The optimal temperature of ChiTg was 40 °C, and the relative activity at 5 °C was above 40.1%. Meanwhile, ChiTg was active and stable from pH 4.0 to 7.0. As an endo-type chitinase, ChiTg exhibited the highest activity with colloidal chitin, then with ball-milled and powdery chitin. In addition, ChiTg showed high efficiency when hydrolyzing colloidal chitin at different temperatures, and the end products were mainly composed of COSs with one to three degrees of polymerization. Furthermore, the results of bioinformatics analysis revealed that ChiTg belongs to the GH18 family, and its acidic surface and the flexible structure of its catalytic site may contribute to its high activity in cold conditions. The results of this study provide a cold-active and efficient chitinase and ideas for its application regarding the preparation of COSs from colloidal chitin.

Serendipita indica chitinase protects rice from the blast and bakanae diseases

Serendipita indica, a multifunctional and useful endophyte fungus, has been intensively investigated in promoting plant growth and resistance towards biotic and abiotic stress. Multiple chitinases from microorganisms or plants have been identified to have a high antifungal activity as a biological control. However, chitinase of S. indica still needs to be characterized. We functionally characterized a chitinase (SiChi) in S. indica. The result showed that the purified SiChi protein confers high chitinase activity; importantly, SiChi inhibits the conidial germination of Magnaporthe oryzae and Fusarium moniliforme. After the successful colonization of rice roots by S. indica, both the rice blast disease and bakanae disease were significantly reduced. Interestingly, the purified SiChi could promptly induce rice disease resistance towards M. oryzae and F. moniliforme pathogens when sprayed on rice leaves. Like S. indica, SiChi could upregulate rice pathogen-resistant proteins and defense enzymes. In conclusion, chitinase of S. indica has direct antifungal activity and indirect induced resistance activity, implying an efficient and economic strategy for rice disease control by applying S. indica and SiChi.

Characterization of chitinases from the GH18 gene family in the myxomycete Physarum polycephalum

BACKGROUND

Physarum polycephalum is an unusual macroscopic myxomycete expressing a large range of glycosyl hydrolases. Among them, enzymes from the GH18 family can hydrolyze chitin, an important structural component of the cell walls in fungi and in the exoskeleton of insects and crustaceans.

METHODS

Low stringency sequence signature search in transcriptomes was used to identify GH18 sequences related to chitinases. Identified sequences were expressed in E. coli and corresponding structures modelled. Synthetic substrates and in some cases colloidal chitin were used to characterize activities.

RESULTS

Catalytically functional hits were sorted and their predicted structures compared. All share the TIM barrel structure of the GH18 chitinase catalytic domain, optionally fused to binding motifs, such as CBM50, CBM18, and CBM14, involved in sugar recognition. Assessment of the enzymatic activities following deletion of the C-terminal CBM14 domain of the most active clone evidenced a significant contribution of this extension to the chitinase activity. A classification based on module organization, functional and structural criteria of characterized enzymes was proposed.

CONCLUSIONS

Physarum polycephalum sequences encompassing a chitinase like GH18 signature share a modular structure involving a structurally conserved catalytic TIM barrels decorated or not by a chitin insertion domain and optionally surrounded by additional sugar binding domains. One of them plays a clear role in enhancing activities toward natural chitin.

GENERAL SIGNIFICANCE

Myxomycete enzymes are currently poorly characterized and constitute a potential source for new catalysts. Among them glycosyl hydrolases have a strong potential for valorization of industrial waste as well as in therapeutic field.

A novel lytic polysaccharide monooxygenase from enrichment microbiota and its application for shrimp shell powder biodegradation

Lytic polysaccharide monooxygenases (LPMO) are expected to change the current status of chitin resource utilization. This study reports that targeted enrichment of the microbiota was performed with chitin by the selective gradient culture technique, and a novel LPMO (M2822) was identified from the enrichment microbiota metagenome. First, soil samples were screened based on soil bacterial species and chitinase biodiversity. Then gradient enrichment culture with different chitin concentrations was carried out. The efficiency of chitin powder degradation was increased by 10.67 times through enrichment, and chitin degradation species Chitiniphilus and Chitinolyticbacter were enriched significantly. A novel LPMO (M2822) was found in the metagenome of the enriched microbiota. Phylogenetic analysis showed that M2822 had a unique phylogenetic position in auxiliary activity (AA) 10 family. The analysis of enzymatic hydrolysate showed that M2822 had chitin activity. When M2822 synergized with commercial chitinase to degrade chitin, the yield of N-acetyl glycosamine was 83.6% higher than chitinase alone. The optimum temperature and pH for M2822 activity were 35°C and 6.0. The synergistic action of M2822 and chitin-degrading enzymes secreted by Chitiniphilus sp. LZ32 could efficiently hydrolyze shrimp shell powder. After 12 h of enzymatic hydrolysis, chitin oligosaccharides (COS) yield reached 4,724 μg/mL. To our knowledge, this work is the first study to mine chitin activity LPMO in the metagenome of enriched microbiota. The obtained M2822 showed application prospects in the efficient production of COS.

Prospects of chitinase in sustainable farming and modern biotechnology: an update on recent progress and challenges

Chitinases are multifunctional biocatalysts for the pest control and useful in modern biotechnology and pharmaceutical industries. Chemical-based fungicides and insecticides have caused more severe effects on environment and human health. Many pathogenic fungal species and insects became resistant to the chemical pesticides. The resistant fungi emerged as a multidrug resistant also and less susceptible insects are not possible to control adequately. Chitinases have an immense potential to be exploited as a biopesticide against fungi and insects. The direct use of chitinase in liquid formulation or whole microbial enzyme producing cells, both act as antagonistically against the pests. Chitinase can disintegrate the fungal cell wall and insect integument that holds the chitin as a vital structural component. Moreover, chitinase is applied for the synthesis of pharmaceutically important chitooligosaccharides. Chitinase producing microbes have the huge potential to utilize against the waste management of sea food remains like shells of crustaceans. Chitinase is valuable for the synthesis of protoplasts from industrially important fungi, further it act as the biocontrol agent of malaria and dengue fever causing larvae of mosquitoes. Chitinases also have been successfully used in wine and single cell protein producing industries. Present review is illustrating the updated information on the state of the art of different applications of chitinases in agriculture and biotechnology industry. It also bestows the understanding to the readers about the areas of extensively studied and the field where there is still much left to be done.

Synergic chitin degradation by Streptomyces sp. SCUT-3 chitinases and their applications in chitinous waste recycling and pathogenic fungi biocontrol

The genus Streptomyces comprises the most important chitin decomposers in soil and revealing their chitinolytic machinery is beneficial for the conversion of chitinous wastes. Streptomyces sp. SCUT-3, a chitin-hydrolyzing and a robust feather-degrading bacterium, was isolated previously. The potential chitin-degrading enzymes produced by SCUT-3 were analyzed in the present study. Among these enzymes, three chitinases were successfully expressed in Pichia pastoris at comparatively high yields of 4.8 U/mL (SsExoChi18A), 11.2 U/mL (SsExoChi18B), and 17.8 U/mL (SsEndoChi19). Conserved motifs and constructive 3D structures of these three exo- and endochitinases were also analyzed. These chitinases hydrolyzed colloidal chitin to chitin oligomers. SsExoChi18A showed apparent synergic effects with SsEndoChi19 in colloidal chitin and shrimp shell hydrolysis, with an improvement of 29.3 % and 124.9 %, respectively. Compared with SsExoChi18B and SsEndoChi19, SsExoChi18A exhibited the strongest antifungal effects against four plant pathogens by inhibiting mycelial growth and spore germination. This study provided good candidates for chitinous waste-processing enzymes and antifungal biocontrol agents. These synergic chitin-degrading enzymes of SCUT-3 are good targets for its further genetical modification to construct super chitinous waste-degrading bacteria with strong abilities to hydrolyze both protein and chitin, thereby providing a direction for the future path of the chitinous waste recycling industry.

Identification, cloning, and characterization of a novel chitinase from leaf-cutting ant Atta sexdens: An enzyme with antifungal and insecticidal activity

Chitinases are enzymes that degrade chitin, a polysaccharide found in the exoskeleton of insects, fungi, yeast, and internal structures of other vertebrates. Although chitinases isolated from bacteria, fungi and plants have been reported to have antifungal or insecticide activities, chitinases from insects with these activities have been seldomly reported. In this study, a leaf-cutting ant Atta sexdens DNA fragment containing 1623 base pairs was amplified and cloned into a vector to express the protein (AsChtII-C4B1) in Pichia pastoris. AsChtII-C4B1, which contains one catalytic domain and one carbohydrate-binding module (CBM), was secreted to the extracellular medium and purified by ammonium sulfate precipitation followed by nickel column chromatography. AsChtII-C4B1 showed maximum activity at pH 5.0 and 55 °C when tested against colloidal chitin substrate and maintained >60% of its maximal activity in different temperatures during 48 h. AsChtII-C4B1 decreased the survival of Spodoptera frugiperda larvae fed with an artificial diet that contained AsChtII-C4B1. Our results have indicated that AsChtII-C4B1 has a higher effect on larva-pupa than larva-larva molts. AsChtII-C4B1 activity targets more specifically the growth of filamentous fungus than yeast. This work describes, for the first time, the obtaining a recombinant chitinase from ants and the characterization of its insecticidal and antifungal activities.

Strain improvement of Trichoderma harzianum for enhanced biocontrol capacity: Strategies and prospects

In the control of plant diseases, biocontrol has the advantages of being efficient and safe for human health and the environment. The filamentous fungus Trichoderma harzianum and its closely related species can inhibit the growth of many phytopathogenic fungi, and have been developed as commercial biocontrol agents for decades. In this review, we summarize studies on T. harzianum species complex from the perspective of strain improvement. To elevate the biocontrol ability, the production of extracellular proteins and compounds with antimicrobial or plant immunity-eliciting activities need to be enhanced. In addition, resistance to various environmental stressors should be strengthened. Engineering the gene regulatory system has the potential to modulate a variety of biological processes related to biocontrol. With the rapidly developing technologies for fungal genetic engineering, T. harzianum strains with increased biocontrol activities are expected to be constructed to promote the sustainable development of agriculture.

Biochemical purification and characterization of a truncated acidic, thermostable chitinase from marine fungus for N-acetylglucosamine production

N-acetylglucosamine (GlcNAc) is widely used in nutritional supplement and is generally produced from chitin using chitinases. While most GlcNAc is produced from colloidal chitin, it is essential that chitinases be acidic enzymes. Herein, we characterized an acidic, highly salinity tolerance and thermostable chitinase AfChiJ, identified from the marine fungus Aspergillus fumigatus df673. Using AlphaFold2 structural prediction, a truncated Δ30AfChiJ was heterologously expressed in E. coli and successfully purified. It was also found that it is active in colloidal chitin, with an optimal temperature of 45°C, an optimal pH of 4.0, and an optimal salt concentration of 3% NaCl. Below 45°C, it was sound over a wide pH range of 2.0–6.0 and maintained high activity (≥97.96%) in 1–7% NaCl. A notable increase in chitinase activity was observed of Δ30AfChiJ by the addition of Mg²⁺, Ba²⁺, urea, and chloroform. AfChiJ first decomposed colloidal chitin to generate mainly N-acetyl chitobioase, which was successively converted to its monomer GlcNAc. This indicated that AfChiJ is a bifunctional enzyme, composed of chitobiosidase and β-N-acetylglucosaminidase. Our result suggested that AfChiJ likely has the potential to convert chitin-containing biomass into high-value added GlcNAc.

The Discovery, Enzymatic Characterization and Functional Analysis of a Newly Isolated Chitinase from Marine-Derived Fungus Aspergillus fumigatus df347

In order to discover a broad-specificity and high stability chitinase, a marine fungus, Aspergillus fumigatus df347, was identified in the sediments of mangrove wetlands in Qinzhou Bay, China. The chitinase gene (AfChi28) from A. fumigatus df347 was cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme AfChi28 was purified and characterized. AfChi28 is an acido-halotolerant- and temperature-resistant bifunctional enzyme with both endo- and exo-cleavage functions. Its enzymatic products are mainly GlcNAc, (GlcNAc)2, (GlcNAc)3 and (GlcNAc)4. Na+, Mg2+, K+, Ca2+ and Tris at a concentration of 50 mM had a strong stimulatory effect on AfChi28. The crude enzyme and pure enzyme exhibited the highest specific activity of 0.737 mU/mg and 52.414 mU/mg towards colloidal chitin. The DxDxE motif at the end of strand β5 and with Glu154 as the catalytic residue was verified by the AlphaFold2 prediction and sequence alignment of homologous proteins. Moreover, the results of molecular docking showed that molecular modeling of chitohexaose was shown to bind to AfChi28 in subsites −4 to +2 in the deep groove substrate-binding pocket. This study demonstrates that AfChi28 is a promising chitinase for the preparation of desirable chitin oligosaccharides, and provides a foundation for elucidating the catalytic mechanism of chitinases from marine fungi.

Recent Developments in Industrial Mycozymes: A Current Appraisal

Fungi, being natural decomposers, are the most potent, ubiquitous and versatile sources of industrial enzymes. About 60% of market share of industrial enzymes is sourced from filamentous fungi and yeasts. Mycozymes (myco-fungus; zymes-enzymes) are playing a pivotal role in several industrial applications and a number of potential applications are in the offing. The field of mycozyme production, while maintaining the old traditional methods, has also witnessed a sea change due to advents in recombinant DNA technology, optimisation protocols, fermentation technology and systems biology. Consolidated bioprocessing of abundant lignocellulosic biomass and complex polysaccharides is being explored at an unprecedented pace and a number of mycozymes of diverse fungal origins are being explored using suitable platforms. The present review attempts to revisit the current status of various mycozymes, screening and production strategies and applications thereof.

Current Perspectives on Chitinolytic Enzymes and Their Agro-Industrial Applications

Chitinases are a large and diversified category of enzymes that break down chitin, the world's second most prevalent polymer after cellulose. GH18 is the most studied family of chitinases, even though chitinolytic enzymes come from a variety of glycosyl hydrolase (GH) families. Most of the distinct GH families, as well as the unique structural and catalytic features of various chitinolytic enzymes, have been thoroughly explored to demonstrate their use in the development of tailor-made chitinases by protein engineering. Although chitin-degrading enzymes may be found in plants and other organisms, such as arthropods, mollusks, protozoans, and nematodes, microbial chitinases are a promising and sustainable option for industrial production. Despite this, the inducible nature, low titer, high production expenses, and susceptibility to severe environments are barriers to upscaling microbial chitinase production. The goal of this study is to address all of the elements that influence microbial fermentation for chitinase production, as well as the purifying procedures for attaining high-quality yield and purity.

Isolation and Evaluation of Rhizosphere Actinomycetes With Potential Application for Biocontrolling Fusarium Wilt of Banana Caused by Fusarium oxysporum f. sp. cubense Tropical Race 4

Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense tropical race 4 (TR4) is globally one of the most destructive soil-borne fungal diseases. Biological control using environmental microorganisms is considered as an alternative and sustainable strategy. Actinomycetes have the potential to explore biocontrol agents due to their production of diverse metabolites. The isolation and identification of high-efficiency and broad-spectrum antagonistic actinomycetes are the key for the application of biocontrol agents. In the present study, 60 actinomycetes were obtained from the rhizosphere soil of Machilus pingii in the primitive ecological natural reserve of Hainan province, China. Seventeen isolates and their extracts exhibited significant antifungal activity against F. oxysporum TR4. Particularly, strain BITDG-11 with the strongest inhibition ability had a broad-spectrum antifungal activity. The assay of its physiological and biochemical profiles showed that strain BITDG-11 had the ability to produce IAA and siderophores and had a positive response to gelatin liquefaction and nitrate reduction. Enzyme activities of chitinase, β-1,3-glucanase, lipase, and urease were also detected. Average nucleotide identity calculated by comparison with the standard strain genome of Streptomyces albospinus JCM3399 was 86.55% below the novel species threshold, suggesting that the strain could be a novel species. In addition, Streptomyces BITDG-11 obviously reduced the disease index of banana plantlets and promoted plant growth at 45 days post inoculation. The higher and lasting expression levels of defense genes and activities of antioxidant enzymes were induced in the roots of banana. Genome sequencing revealed that the Streptomyces BITDG-11 chromosome contained large numbers of conserved biosynthesis gene clusters encoding terpenes, non-ribosomal peptides, polyketides, siderophores, and ectoines. Fifteen bioactive secondary metabolites were further identified from Streptomyces BITDG-11 extract by gas chromatography-mass spectrometry. Dibutyl phthalate demonstrating a strong antifungal activity was the major compound with the highest peak area. Hence, Streptomyces sp. BITDG-11 has a great potential to become an essential constituent of modern agricultural practice as biofertilizers and biocontrol agents.

Microbial chitinases: properties, enhancement and potential applications

Chitinases are a category of hydrolytic enzymes that catalyze chitin and are formed by a wide variety of microorganisms. In nature, microbial chitinases are primarily responsible for chitin decomposition and play a vital role in the balance of carbon and nitrogen ratio in the ecosystem. The physicochemical attributes and the source of chitinase are the main bases that determine their functional characteristics and hydrolyzed products. Several chitinases have been reported and characterized, and they obtain a wider consideration for their utilization in a large number of uses such as in agriculture, food, environment, medicine and pharmaceutical companies. The antifungal and insecticidal impacts of several chitinases have been extensively studied, aiming to protect crops from phytopathogenic fungi and insects. Chitooligosaccharides synthesized by chitin degradation have been shown to improve human health through their antimicrobial, antioxidant, anti-inflammatory and antitumor properties. This review aims at investigating chitinase production, properties and their potential applications in various biotechnological fields.

A Broad-Specificity Chitinase from Penicillium oxalicum k10 Exhibits Antifungal Activity and Biodegradation Properties of Chitin

Penicillium oxalicum k10 isolated from soil revealed the hydrolyzing ability of shrimp chitin and antifungal activity against Sclerotinia sclerotiorum. The k10 chitinase was produced from a powder chitin-containing medium and purified by ammonium sulfate precipitation and column chromatography. The purified chitinase showed maximal activity toward colloidal chitin at pH 5 and 40 °C. The enzymatic activity was enhanced by potassium and zinc, and it was inhibited by silver, iron, and copper. The chitinase could convert colloidal chitin to N-acetylglucosamine (GlcNAc), (GlcNAc)2, and (GlcNAc)3, showing that this enzyme had endocleavage and exocleavage activities. In addition, the chitinase prevented the mycelial growth of the phytopathogenic fungi S. sclerotiorum and Mucor circinelloides. These results indicate that k10 is a potential candidate for producing chitinase that could be useful for generating chitooligosaccharides from chitinous waste and functions as a fungicide.

Biochemical characterization of a novel acidic chitinase with antifungal activity from Paenibacillus xylanexedens Z2-4

A chitinase gene (PxChi52) from Paenibacillus xylanexedens Z2-4 was cloned and heterologously expressed in Escherichia coli BL21 (DE3). PxChi52 shared the highest identity of 91% with a glycoside hydrolase family 18 chitinase (ChiD) from Bacillus circulans. The recombinant enzyme (PxChi52) was purified and biochemically characterized. PxChi52 had a molecular mass of 52.8 kDa. It was most active at pH 4.5 and 65 °C, respectively, and stable in a wide pH range of 4.0-13.0 and up to 50 °C. The enzyme exhibited the highest specific activity of 16.0 U/mg towards colloidal chitin, followed by ethylene glycol chitin (5.4 U/mg) and ball milled chitin (0.4 U/mg). The K_m and V_max values of PxChi52 towards colloidal chitin were determined to be 3.06 mg/mL and 71.38 U/mg, respectively, PxChi52 hydrolyzed colloidal chitin and chitooligosaccharides with degree of polymerization 2-5 to release mainly N-acetyl chitobiose. In addition, PxChi52 displayed inhibition effects on the growth of some phytopathogenic fungi, including Alternaria alstroemeriae, Botrytis cinerea, Rhizoctonia solani, Sclerotinia sclerotiorum and Valsa mali. The unique properties of PxChi52 may enable it potential application in agriculture field as a biocontrol agent.

Screening and Identification of Sponge-Associated Chitinolytic Bacteria by Forming Chitosan from Manado Bay, Indonesia

BACKGROUND AND OBJECTIVE

Chitosan can be produced through the enzymatic process catalyzed by chitin deacetylase which can be produced by bacteria. The biotransformation of chitin to chitosan by bacteria is interesting because the process is economical and environmentally friendly. This study described the potential of sponge-associated bacterium capability in degrading chitin and forming chitosan.

MATERIALS AND METHODS

The bacteria were isolated from sponge Cribrochalina sp. at Manado Bay, Indonesia. In the screening of the chitinase activity of bacteria, chitin media was used. Meanwhile, the transformation of chitin to chitosan was tested by using Chitinase Degrading Activity media. Molecular identification of bacteria was based on 16S rRNA gene sequences.

RESULTS

The results showed that the SS1, SS2, SS3, SS4 and SS5 bacterial isolates could degrade chitin based on chitinolytic indexes. These five bacteria could also form chitosan exhibited through the presence of chitosan in the form of precipitation in the fermented broth of bacteria. SS1 had the highest chitinase activity based on the chitinolytic index identified as Bacillus subtilis (100% identity), hence it is called B. subtilis strain SS1. The partial rRNA gene sequences data were deposited at GenBank under accession number MN999892.

CONCLUSION

The bacteria strain isolated from Cribrochalina sp. can be utilized in degrading chitin and form chitosan which could be a promising candidate for an economical and eco-friendly process of chitosan.

Biochemical characterization of a GH19 chitinase from Streptomyces alfalfae and its applications in crystalline chitin conversion and biocontrol

Chitinases play crucial roles in enzymatic conversion of chitin and biocontrol of phytopathogenic fungi. Herein, a chitinase of glycoside hydrolase (GH) family 19, SaChiB, was cloned from Streptomyces alfalfae ACCC 40021 and expressed in Escherichia coli BL21(DE3). The purified SaChiB displayed maximal activities at 45 °C and pH 8.0, and showed good stability up to 55 °C and in the range of pH 4.0-11.0, respectively. It exhibited substrate specificity towards chitin and chitooligosaccharides (degree of polymerization 3-6) with the endo-cleavage manner. In combination with the N-acetyl hexosaminidase SaHEX, it yielded a conversion rate of 95.2% from chitin powder to N-acetyl-D-glucosamine in 8 h and a product purity of >98.5%. Furthermore, the enzyme strongly inhibited the growth of tested pathogenic fungi. These results indicated that SaChiB has the great potential for applications in the conversion of raw chitinous waste in industries as well as the biocontrol of fungal diseases in agriculture.

A thermophilic chitinase 1602 from the marine bacterium Microbulbifer sp. BN3 and its high-level expression in Pichia pastoris

Chitinases play an important role in many industrial processes, including the preparation of oligosaccharides with potential applications. In the present study, a 1,713 bp gene of Chi1602, derived from a marine bacterium Microbulbifer sp. BN3, encoding a GH18 family chitinase, was expressed at high levels in Pichia pastoris. Distinct from most of the marine chitinases, the recombinant chitinase 1602 exhibited maximal activity at 60 °C and over a broad pH range between 5.0 and 9.0, and was stable at 50 °C and over the pH range 4.0-9.0. The hydrolytic products derived from colloidal chitins comprised mainly (GlcNAc)₂ and GlcNAc, indicating that rChi1602 is a GH18 processive chitinase in conformity with its hypothetical structure. However, rChi1602 showed traces of β-N-acetylglucosaminidase activity on substrates such as powder chitin, chitosan, and ethylene glycol chitin. The thermophilic rChi1602, which manifests adaptation to a wide pH range and can be expressed at a high level in P. pastoris, is advantageous for applications in industrial processes.

Immunomodulatory Effects of N-Acetyl Chitooligosaccharides on RAW264.7 Macrophages

The ongoing development of new production methods may lead to the commercialization of N-acetyl chitooligosaccharides (NACOS), such as chitosan oligosaccharides (COS). The bioactivity of NACOS, although not well detailed, differs from that of COS, as they have more acetyl groups than COS. We used two enzymatically produced NACOS with different molecular compositions and six NACOS (NACOS1–6) with a single degree of polymerization to verify their immunomodulatory effects on the RAW264.7 macrophage cell line. We aimed to identify any differences between COS and various NACOS with a single degree of polymerization. The results showed that NACOS had similar immune enhancement effects on RAW264.7 cells as COS, including the generation of reactive oxygen species (ROS), phagocytotic activity, and the production of pro-inflammation cytokines (IL-1β, IL-6, and TNF-α). However, unlike COS and lipopolysaccharide (LPS), NACOS1 and NACOS6 significantly inhibited nitric oxide (NO) production. Besides their immune enhancement effects, NACOS also significantly inhibited the LPS-induced RAW264.7 inflammatory response with some differences between various polymerization degrees. We confirmed that the NF-κB pathway is associated with the immunomodulatory effects of NACOS on RAW264.7 cells. This study could inform the application of NACOS with varying different degrees of polymerization in human health.

Endo-chitinase Chit33 specificity on different chitinolytic materials allows the production of unexplored chitooligosaccharides with antioxidant activity

The biological activity of chitooligosaccharides (COS) has made them targets for industrial and medical sectors. In this work, endo-chitinase Chit33 from Trichoderma harzianum CECT 2413 was expressed in Pichia pastoris GS115 to levels never achieved before (630 mg/L; 3.3 U/mL), without its biochemical characteristics being substantially affected. Chit33 produced a mixture of fully and partially acetylated COS from different chitin derivatives. HPAEC-PAD Chromatography and mass spectrometry analyses showed that (GlcNAc)₄ and GlcN-(GlcNAc)₂ were mainly produced from colloidal chitin and chitosan, respectively. COS in reaction mixtures were fragmented according to their size and their antioxidant activity analyzed by reducing power and free radical scavenging activity essays. The highest antioxidant activity was achieved with COS in the range of 0.5-2 and 2-10 kDa produced from colloidal chitin and chitosan, respectively, which gives biotechnological potential to both the chitin derivatives of 0.5-10 kDa and the biocatalyst producing them.

Cloning, expression and characterization of a chitinase from Paenibacillus chitinolyticus strain UMBR 0002

Background

Chitinases are enzymes which degrade β-1,4-glycosidid linkages in chitin. The enzymatic degradation of shellfish waste (containing chitin) to chitooligosaccharides is used in industrial applications to generate high-value-added products from such waste. However, chitinases are currently produced with low efficiency and poor tolerance, limiting the industrial utility. Therefore, identifying chitinases with higher enzymatic activity and tolerance is of great importance.

Methods

Primers were designed using the genomic database of Paenibacillus chitinolyticus NBRC 15660. An exochitinase (CHI) was cloned into the recombinant plasmid pET-22b (+) to form pET-22b (+)-CHI, which was transformed into Escherichia coli TOP10 to construct a genomic library. Transformation was confirmed by colony-polymerase chain reaction and electrophoresis. The target sequence was verified by sequencing. Recombinant pET-22b (+)-CHI was transformed into E. coli Rosetta-gami B (DE3) for expression of chitinase. Recombinant protein was purified by Ni-NTA affinity chromatography and enzymatic analysis was carried out.

Results

The exochitinase CHI from P. chitinolyticus strain UMBR 0002 was successfully cloned and heterologously expressed in E. coli Rosetta-gami B (DE3). Purification yielded a 13.36-fold enrichment and recovery yield of 72.20%. The purified enzyme had a specific activity of 750.64 mU mg^-1. The optimum pH and temperature for degradation of colloidal chitin were 5.0 and 45 °C, respectively. The enzyme showed high stability, retaining >70% activity at pH 4.0-10.0 and 25-45 °C (maximum of 90 min). The activity of CHI strongly increased with the addition of Ca²⁺, Mn²⁺, Tween 80 and urea. Conversely, Cu²⁺, Fe³⁺, acetic acid, isoamyl alcohol, sodium dodecyl sulfate and β-mercaptoethanol significantly inhibited enzyme activity. The oligosaccharides produced by CHI from colloidal chitin exhibited a degree of polymerization, forming N-acetylglucosamine (GlcNAc) and (GlcNAc)₂ as products.

Conclusions

This is the first report of the cloning, heterologous expression and purification of a chitinase from P. chitinolyticus strain UMBR 0002. The results highlight CHI as a good candidate enzyme for green degradation of chitinous waste.

Purification, characterization and cloning of a chitinase from Stenotrophomonas rhizophila G22

In the presented research the extracellular chitinase of Stenotrophomonas rhizophila G22 was biochemically and molecularly characterized. The studied enzyme was purified from a 72-h bacterial culture about 14 times, with a recovery of 63%. The molecular weight of the purified protein was estimated at 50 kDa by SDS-PAGE. The enzyme showed high activity against colloidal chitin. Significantly lower activities were observed with native chitin powder and chitosan. Adsorption of the enzyme to colloidal chitin and to powdered chitin at the level of 75% and 37%, respectively, was observed after 30 min of reaction. Optimum temperature and pH were 37 °C and 5.9, respectively. The enzyme demonstrated higher activity against nitrophenyl-β d N, N', N″-triacetylchitotriose and approx. 5 times lower activity for 4-nitrophenyl-N, N'-diacetyl-β-d-chitobiose. The enzyme is an endochitinase, which is confirmed by the K _m and V _max values determined in the studies. S. rhizophila G22 endochitinase was inhibited in the presence of cysteine-specific inhibitors, which indicates the role of cysteine moieties in the mechanism of catalysis or in stabilisation of the enzyme molecule. Also Ca²⁺ and Mn²⁺ ions may stabilise the protein's spatial structure. SDS and ions: Fe²⁺, Cu²⁺, Co²⁺, Zn²⁺ inhibited the activity of enzyme. A full-length (2109 bp) gene coding chitinase from S. rhizophila G22 was obtained. Four domains typical for glycoside hydrolase family 18 (GH 18) chitinases were identified: catalytic Gly_18, chitin-binding-ChtBD3, type-III fibronectin-FN3 and polycystic kidney disease domain-PKD domain.

Microbial chitinases: properties, current state and biotechnological applications

Chitinases are a group of hydrolytic enzymes that catalyze chitin, nd are synthesized by a wide variety of organisms. In nature, microbial chitinases are primarily responsible for chitin decomposition. Several chitinases have been reported and characterized, and they are garnering increasing attention for their uses in a wide range of applications. In the food industry, the direct fermentation of seafood, such as crab and shrimp shells, using chitinolytic microorganisms has contributed to increased nutritional benefits through the enhancement of chitin degradation into chitooligosaccharides. These compounds have been demonstrated to improve human health through their antitumor, antimicrobial, immunomodulatory, antioxidant, and anti-inflammatory properties. Moreover, chitinase and chitinous materials are used in the food industry for other purposes, such as the production of single-cell proteins, chitooligosaccharides, N-acetyl D-glucosamines, biocontrol, functional foods, and various medicines. The functional properties and hydrolyzed products of chitinase, however, depend upon its source and physicochemical characteristics. The present review strives to clarify these perspectives and critically discusses the advances and limitations of microbial chitinase in the further production of functional foods.

A potent chitin-hydrolyzing enzyme from Myrothecium verrucaria affects growth and development of Helicoverpa armigera and plant fungal pathogens

Chitin, a crucial structural and functional component of insects and fungi, serves as a target for pest management by utilizing novel chitinases. Here, we report the biocontrol potential of recombinant Myrothecium verrucaria endochitinase (rMvEChi) against insect pest and fungal pathogens. A complete ORF of MvEChi (1185 bp) was cloned and heterologously expressed in Escherichia coli. Structure based sequence alignment of MvEChi revealed the presence of conserved domains SXGG and DXXDXDXE specific for GH-18 family, involved in substrate binding and catalysis, respectively. rMvEChi (46.6 kDa) showed optimum pH and temperature as 7.0 and 30 °C, respectively. Furthermore, rMvEChi remained stable within the pH range of 6.0 to 8.0 and up to 40 °C. rMvEChi exhibited k_cat/K_m values of 129.83 × 10³ [(g/L)^-1 s^-1] towards 4MU chitotrioside. Hydrolysis of chitooligosaccharides with various degrees of polymerization (DP) using rMvEChi indicated the release of DP2 as main end product with order of reaction as DP6 > DP5 > DP4 > DP3. Bioassay of rMvEChi against Helicoverpa armigera displayed potent anti-feedant activity and induced mortality. In vitro antifungal activity against plant pathogenic fungi (Ustilago maydis and Bipolaris sorokiniana) exhibited significant inhibition of mycelium growth. These results suggest that MvEChi has significant potential in enzyme-based pest and pathogen management.