Purification, characterization, and molecular cloning of an extracellular chitinase from Bacillus licheniformis stain LHH100 isolated from wastewater samples in Algeria

Enhanced biological activity of chitinase immobilized on cobalt metal-organic framework: Isolation, characterization, and potential applications

Chitinase, an enzyme that hydrolyzes glycosidic bonds in chitin, holds significant potential for industrial applications, including biological control, antifungal treatments, and antibiofilm strategies. In this study, chitinase derived from Planomicrobium sp. (PP133202) was immobilized onto a cobalt metal-organic framework (Co-MOF), and its properties were extensively analyzed using various biological, chemical, and physical characterization techniques. The microbial source was identified via 16S rRNA sequencing, and enzyme activity was optimized under submerged conditions using Response Surface Methodology (RSM). Structural and morphological characterization of the chitinase/Co-MOF complex was conducted through FTIR, SEM, TEM, XPS, XRD, EDX, and surface area analyses. The encapsulation efficiency and loading capacity were determined to be 42 % and 20 %, respectively. Notably, the immobilized chitinase exhibited a threefold increase in enzymatic activity compared to its free form. Additionally, the chitinase/Co-MOF complex demonstrated enhanced biological control efficacy, effectively inhibiting Tribolium castaneum and multiple pathogenic microorganisms, including Pseudomonas aeruginosa, Aspergillus flavus, Aspergillus terreus, and Beauveria bassiana. These findings highlight the potential of chitinase/Co-MOF as a promising agent for antimicrobial and pest control applications.

Construction of Chitinase Complexes Using Self-Assembly Systems for Efficient Hydrolysis of Chitin

Chitin biomass is the second most abundant natural polysaccharide after cellulose on the earth, yet its recalcitrance to degrade and utilize severely limits its application. However, many microorganisms, such as Serratia marcescen, can secrete a range of free chitinases to degrade chitin, though their activity is typically insufficient to meet industrial demands. In this study, we employed self-assembly systems, named SpyTag/SpyCatcher and SnoopTag/SnoopCatcher, to modularize the molecular design of CHB, ChiB, ChiC, and CBP21 derived from S. marcescens ATCC14756, and we successfully constructed a variety of chitinase complexes. The assembled complexes showed higher chitinolytic activity and stability, compared to free chitinase mixture. Moreover, the distinct arrangements and combinations of chitinases within these complexes led to varied activities, suggesting that the spatial proximity and substrate channeling effects contribute to the synergy of chitinase complexes. The findings lay a solid technical foundation for the application of chitinosome in the industrial production of N-acetylglucosamine and chitooligosaccharides.

Production of a new chitinase from Nocardiopsis halophila TN-X8 utilizing bio-waste from the blue swimming crab: enzyme characterization and immobilization

In accordance with the framework of the Circular Blue Bioeconomy in the Mediterranean region, the objective of this study was to evaluate the biotransformation of blue swimming crab (Portunus segnis) residues obtained from the port of Sfax by an extracellular chitinase produced by Nocardiopsis halophila strain TN-X8 isolated from Chott El Jerid (Tozeur, Tunisia). From the analysis of multiple extremophilic Actinomycetota, it was determined that strain TN-X8 exclusively utilized 60 g/L of raw blue swimming crab as its carbon and energy source, achieving a chitinase activity of approximately 950 U/mL following a 6-day incubation period at 40 °C. Pure chitinase, designated as ChiA-Nh30, was obtained after heat treatment, followed by ammonium sulfate fractionation and Sephacryl® S-200 column chromatography. The maximum ChiA-Nh30 activity was observed at pH 3 and 75 °C. Interestingly, compared with cyclohexamidine, ChiA-Nh30 showed a good antifungal effect against four pathogenic fungi. Furthermore, when using colloidal chitin as substrate, ChiA-Nh30 demonstrated a higher degree of catalytic efficiency than the commercially available Chitodextrinase®. In addition, ChiA-Nh30 could be immobilized by applying encapsulation and encapsulation-adsorption techniques. The kaolin and charcoal used acted as excellent binders, resulting in improved ChiA-Nh30 stability. For the immobilized ChiA-Nh30, the yield of N-acetyl-D-glucosamine monomers released from 20% (w/v) blue swimming crab residues increased by 3.1 (kaolin) and 2.65 (charcoal) times, respectively.

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.

Isolation, screening, and identification of chitinase-producing bacterial strains from riverbank soils at Ambo, Western Ethiopia

Chitinases are hydrolytic enzymes that dissolve the glycosidic linkages in chitin. Chitin is a cell wall component of fungi and fund in exoskeleten of worms and arthropods. Chitinase has been applied in agriculture, as a biopesticide for the control of plant fungal infections, in medicine, and in waste management. This research aimed to isolate, screen, and identification of chitinase-producing bacteria from riverbank soils. Twenty nine chitinolytic bacteria were isolated from the river bank soil samples, from which 9 of them had strong chitinolytic properties. Chitinase production was determined by zones of hydrolysis produced after 96 h of incubation at 37 °C. The different bacterial isolates were characterized morphologically, microscopically, and biochemically and finally eight strain were identified at species level by Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI-TOF MS). From the eight, bacterial isolates investigated in this study Stenotrophomonas maltophilia showed the highest chitinase enzyme activity (625 μg/mL) followed by Pseudomonas putida with the enzyme activity of (553 μg/mL) and the least enzyme activity was recorded for Lilliottia amnigena (80 μg/mL). An incubation temperature of 45 °C, neutral pH and an incubation period of 96 h are found to be the optimum condition for the chitinase enzyme production from Stenotrophomonas maltophilia. The results of this study indicated the possibility of the production of chitinase from the chitinolytic bacterial isolates, which was highly useful for a variety of applications, including biocontrol of harmful insects and pathogenic fungi as well as in the biochemical, pharmaceutical, and medical sectors.

The potential of degrading natural chitinous wastes to oligosaccharides by chitinolytic enzymes from two Talaromyces sp. isolated from rotten insects (Hermetia illucens) under solid state fermentation

It is difficult to produce chitin oligosaccharides by hydrolyzing untreated natural chitinous waste directly. In this study, two fungi Talaromyces allahabadensis Hi-4 and Talaromyces funiculosus Hi-5 from rotten black soldier fly were isolated and identified through multigene phylogenetic and morphological analyses. The chitinolytic enzymes were produced by solid state fermentation, and the growth conditions were optimized by combining single-factor and central composite design. The best carbon sources were powder of molting of mealworms (MMP) and there was no need for additional nitrogen sources in two fungi, then the maximum chitinolytic enzyme production of 46.80 ± 3.30 (Hi-4) and 55.07 ± 2.48 (Hi-5) U/gds were achieved after analyzing the 3D response surface plots. Pure chitin (colloidal chitin) and natural chitinous substrates (represented by MMP) were used to optimize degradation abilities by crude enzymes obtained from the two fungi. The optimum temperature for hydrolyzing MMP (40 °C both in two fungi) were lower and closer to room temperature than colloidal chitin (55 °C for Hi-4 and 45 °C for Hi-5). Then colloidal chitin, MMP and the powder of shrimp shells (SSP) were used for analyzing the products after 5-day degradation. The amounts of chitin oligosaccharides from SSP and MMP were about 1/6 (Hi-4), 1/17 (Hi-5) and 1/8 (Hi-4), 1/10 (Hi-5), respectively, in comparison to colloidal chitin. The main components of the products were GlcNAc for colloidal chitin, (GlcNAc)2 for MMP, and oligosaccharides with higher degree of polymerization (4-6) were obtained when hydrolyzing SSP, which is significant for applications in medicine and health products.

Isolation of Chitinolytic Bacteria from European Sea Bass Gut Microbiota Fed Diets with Distinct Insect Meals

Insect meal (IM), recently authorized for use in aquafeeds, positions itself as a promising commodity for aquafeed inclusion. However, insects are also rich in chitin, a structural polysaccharide present in the exoskeleton, which is not digested by fish, resulting in lower fish performance. Through the application of a dietary pressure, this study aimed to modulate European sea bass gut microbiota towards the enrichment of chitinolytic bacteria to allow the isolation of novel probiotics capable of improving the use of IM-containing diets, overcoming chitin drawbacks. Five isoproteic (44%) and isolipidic (18%) diets were used: a fish meal (FM)-based diet (diet CTR), a chitin-supplemented diet (diet CHIT5), and three diets with either 25% of Hermetia illucens and Tenebrio molitor larvae meals (HM25 and TM25, respectively) or H. illucens exuviae meal (diet HEM25) as partial FM substitutes. After an 8-week feeding trial, the results showed a clear modulatory effect towards spore-forming bacteria by HM25 and HEM25 diets, with the latter being responsible for the majority of the chitinolytic fish isolates (FIs) obtained. Sequential evaluation of the FI hemolytic activity, antibiotic resistance, total chitinolytic activity, sporulation, and survival in gastrointestinal-like conditions identified FI645 and FI658 as the most promising chitinolytic probiotics for in vivo application.

A Contemporary Appraisal on Impending Industrial and Agricultural Applications of Thermophilic-Recombinant Chitinolytic Enzymes from Microbial Sources

The ability of chitinases to degrade the second most abundant polymer, chitin, into potentially useful chitooligomers and chitin derivatives has not only rendered them fit for chitinous waste management but has also made them important from industrial point of view. At the same time, they have also been recognized to have an imperative role as promising biocontrol agents for controlling plant diseases. As thermostability is an important property for an industrially important enzyme, various bacterial and fungal sources are being exploited to obtain such stable enzymes. These stable enzymes can also play a role in agriculture by maintaining their stability under adverse environmental conditions for longer time duration when used as biocontrol agent. Biotechnology has also played its role in the development of recombinant chitinases with enhanced activity, thermostability, fungicidal and insecticidal activity via recombinant DNA techniques. Furthermore, a relatively new approach of generating pathogen-resistant transgenic plants has opened new ways for sustainable agriculture by minimizing the yield loss of valuable crops and plants. This review focuses on the potential applications of thermostable and recombinant microbial chitinases in industry and agriculture.

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.

Quantitative single molecule RNA-FISH and RNase-free cell wall digestion in Neurospora crassa

Single molecule RNA-FISH (smFISH) is a valuable tool for analysis of mRNA spatial patterning in fixed cells that is underutilized in filamentous fungi. A primary complication for fixed-cell imaging in filamentous fungi is the need for enzymatic cell wall permeabilization, which is compounded by considerable variability in cell wall composition between species. smFISH adds another layer of complexity due to a requirement for RNase free conditions. Here, we describe the cloning, expression, and purification of a chitinase suitable for supplementation of a commercially available RNase-free enzyme preparation for efficient permeabilization of the Neurospora cell wall. We further provide a method for smFISH in Neurospora which includes a tool for generating numerical data from images that can be used in downstream customized analysis protocols.

The discovery and characterization of a novel chitinase with dual catalytic domains from a Qinghai-Tibetan Plateau wetland soil metagenome

A novel chitinase (P1724) was discovered from a Qinghai-Tibetan plateau microbial metagenome. P1724 contains two GH18 family catalytic domains and is phylogenetically distant from any of the chitinases studied. P1724 and its truncated versions, P1724(∆cGH18) and P1724(∆nGH18), were produced in Escherichia coli and characterized. Using colloidal chitin as substrate, the three recombinant proteins showed maximum hydrolytic activities at 40 °C, pH 5.0-6.0 and 0-0.5 M NaCl, and were cold adaptive, as they remained active at 4 °C; their chitinase activities were decreased with the presence of Cu²⁺ and EDTA, but increased with Ba²⁺ and Ca²⁺; they all showed both chitobiosidase and endochitinase activities. Compared to P1724(∆nGH18), P1724 and P1724(∆cGH18) shared more similarities in temperature and pH stabilities, NaCl tolerance, and substrate affinity, suggesting the N-terminal GH18 domain contributed more than the C-terminal GH18 did in biochemical characteristics of P1724. k_cat/K_m value of P1724 was significantly higher than the sum values of P1724(∆cGH18) and P1724(∆nGH18), which indicated that two GH18 domains of P1724 worked cooperatively in degrading chitin. This study has not only broadened the understanding of unknown chitinases in nature but also discussed the strategy of adding additional catalytic domains in enzyme engineering.

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.

Identification and Characterization of a Newly Isolated Chitinase-Producing Strain Bacillus licheniformis SSCL-10 for Chitin Degradation

Chitinases or chitinolytic enzymes have different applications in the field of medicine, agriculture, and industry. The present study is aimed at developing an effective hyperchitinase-producing mutant strain of novel Bacillus licheniformis. A simple and rapid methodology was used for screening potential chitinolytic microbiota by chemical mutagenesis with ethylmethane sulfonate and irradiation with UV. There were 16 mutant strains exhibiting chitinase activity. Out of the chitinase-producing strains, the strain with maximum chitinase activity was selected, the protein was partially purified by SDS-PAGE, and the strain was identified as Bacillus licheniformis (SSCL-10) with the highest specific activity of 3.4 U/mL. The induced mutation model has been successfully implemented in the mutant EMS-13 (20.2 U/mL) that produces 5-6-fold higher yield of chitinase, whereas the mutant UV-11 (13.3 U/mL) has 3-4-fold greater chitinase activity compared to the wild strain. The partially purified chitinase has a molecular weight of 66 kDa. The wild strain (SSCL-10) was identified as Bacillus licheniformis using 16S rRNA sequence analysis. This study explores the potential applications of hyperchitinase-producing bacteria in recycling and processing chitin wastes from crustaceans and shrimp, thereby adding value to the crustacean industry.

Biochemical and molecular characterization of an acido-thermostable endo-chitinase from Bacillus altitudinis KA15 for industrial degradation of chitinous waste

This paper reports the isolation and identification of an acido-thermostable chitinase (ChiA-Ba43) which was purified, from the culture liquid of Bacillus altitudinis strain KA15, and characterized. Purification of ChiA-Ba43 produced a 69.6-fold increase in the specific activity (120,000 U/mg) of the chitinase, with a yield of 51% using colloidal chitin as substrate. ChiA-Ba43 was found to be a monomeric protein with a molecular mass of 43,190.05 Da as determined by MALDI-TOF/MS. N-terminal sequence of the first 27 amino-acids (aa) of ChiA-Ba43 displayed homology to chitinases from other Bacillus species. Interestingly, ChiA-Ba43 exhibited optimum pH and temperature of 4-5.5 and 85 °C, respectively. Thin-layer chromatography (TLC) showed that the final hydrolyzed products of the enzyme from chitin-oligosaccharides and colloidal chitin are a mixture of (GlcNAc)₂, (GlcNAc)₃, (GlcNAc)₄, and (GlcNAc)₅, which indicates that ChiA-Ba43 possesses an endo-acting function. More interestingly, compared to ChiA-Mt45, ChiA-Hh59, Chitodextrinase®, N-acetyl-β-glucosaminidase®, and ChiA-65, ChiA-Ba43 demonstrated a high level of catalytic efficiency and outstanding tolerance towards various organic solvents. The chiA-Ba43 gene (1332 bp) encoding ChiA-Ba43 (409 aa) was cloned, sequenced, and expressed in Escherichia coli strain HB101. The biochemical properties of the recombinant chitinase (rChiA-Ba43) were equivalent to those of the natively expressed enzyme. These properties make ChiA-Ba43 an ideal candidate for industrial bioconversion of chitinous waste.

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.

Partial purification and characterization of chitinase produced by Bacillus licheniformis B307

The optimal conditions required for chitinase production from Bacillus licheniformis B307 strain, obtained from Syrian soil, were studied. Optimization experiments were carried out under submerged fermentation conditions, and colloidal chitin was the source of carbon. Luria broth medium supplied with 0.5% colloidal chitin was the optimum medium for chitinase production. The maximum chitinase yield was obtained at 30 °C, pH6, incubation time 14 days, and 150 rpm. The optimum chitinase activity was achieved at 60 °C and pH6. The chitinase activity with unmodified medium was 1.9 U/mL which then enhanced about eight folds to reach 14.2 U/mL under optimized submerged fermentation conditions. An extracellular chitinase of Bacillus licheniformis B307 was partially purified using ammonium sulfate precipitation followed by concentration with various sizes of concentrator tubes. The chitinase was partially purified 8.24 fold and specific enzyme activity increased 2.08 fold (2 U/mg). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of partial purified chitinase exhibited a molecular weight (M_r) near to 36 and 42kDa. These results make it possible to invest in this strain to produce chitinase to be used as antifungal, food additives and other applications.

Functional expression of recombinant hybrid enzymes composed of bacterial and insect's chitinase domains in E. coli

To elucidate the functional alteration of the recombinant hybrid chitinases composed of bacterial and insect's domains, we cloned the constitutional domains from chitinase-encoding cDNAs of a bacterial species, Bacillus thuringiensis (BtChi) and a lepidopteran insect species, Mamestra brassicae (MbChi), respectively, swapped one's leading signal peptide (LSP) - catalytic domain (CD) - linker region (LR) (LCL) with the other's chitin binding domain (ChBD) between the two species, and confirmed and analyzed the functional expression of the recombinant hybrid chitinases and their chitinolytic activities in the transformed E. coli strains. Each of the two recombinant cDNAs, MbChi's LCL connected with BtChi's ChBD (MbLCL-BtChBD) and BtChi's LCL connected with MbChi's ChBD (BtLCL-MbChBD), was successfully introduced and expressed in E. coli BL21 strain. Although both of the two hybrid enzymes were found to be expressed by SDS-PAGE and Western blotting, the effects of the introduced genes on the chitin metabolism appear to be dramatically different between the two transformed E. coli strains. BtLCL-MbChBD remarkably increased not only the cell proliferation rate, extracellular and cellular chitinolytic activity, but also cellular glucosamine and N-acetylglucosamine levels, while MbLCL-BtChBD showed about the same profiles in the three tested subjects as those of the strains transformed with each of the two native chitinases, indicating that a combination of the bacterial CD of TIM barrel structure with characteristic six cysteine residues and insect ChBD2 including a conserved six cysteine-rich region (6C) enhances the attachment of the enzyme molecule to chitin compound by MbChBD, and so increases the catalytic efficiency of bacterial CD.

A comparison of chitosan properties after extraction from shrimp shells by diluted and concentrated acids

Chitosan and chitin are mainly extracted from shells of fish such as lobsters, crabs or shrimps. Originally, the raw material and the two compounds are identical. This study aims to show the acid concentration effect on chitosan extraction from shrimp shells between concentrated and diluted acid; on surface morphology, thermal resistance, structural, elemental composition, optical and opto-electronic properties. It also aims to reduce the production time and increase the quantity. We focused mainly on comparing between Physico-chemical properties of chitosans extracted by diluted (1M) and concentrated (20%) Chloric acids, and sometimes we compare by other concentrated acids like nitric acid (70%) and sulphuric acid (98%). We performed the product's characterization by various tools such as: X-ray diffraction (XRD) spectroscopy, X-ray fluorescence (XRF) analysis, UV-Visible spectroscopy, Fourier Transformed Infra-Red (FTIR), Raman Spectroscopy, Thermogravimetry and Derivative Thermogravimetry (TG/DTG), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) analysis. The elemental analysis (XRF and EDX). The results showed that all chitosan samples we gained are good about 80% degree of deacetylation, and pure mostly composed by carbon between (15,02% - 45.55%), nitrogen (4,17% - 12.28%) and oxygen (42.16% and 81.25%), with appearance of essential peaks for chitosan in Raman analysis: 470 cm⁻¹ → ν(C-C(=O)-C), 1000 cm⁻¹ → ν(C-H), 1800 cm⁻¹ → δ(C=CCOOR), δ(C=O), 2630 cm⁻¹ → δ(CH) rings, 3250 cm⁻¹ → ν(NH₂). All our chitosan particles are ultrafine nanoscale between 8 and 34 nm.

Improving the thermostability and activity of Paenibacillus pasadenensis chitinase through semi-rational design

Chitinase is a promising biocatalyst for chitin biotransformation in the field of recalcitrant biomass degradation. Excellent catalytic performance is conducive to its commercial utilization. In this work, sequence- and structure-based semi-rational design was performed to evolve the thermostability and activity of a previously identified chitinase PpChi1 from Paenibacillus pasadenensis CS0611. After combinational mutagenesis, the mutant S244C-I319C/T259P with disulfide bond introduction and proline substitution exhibited higher specific activity at higher temperature, 26.3-fold in half-life value at 50 °C, and a 7.9 °C rise in half-inactivation temperature T_1/2^15min compared to the wild-type enzyme. The optimal reaction temperature of the mutant was shifted from 45 °C to 52.5 °C. Molecular dynamic simulation and structure analysis confirmed that these improvements of the mutant were attributed to its stabilized folding form, possibly caused by the decreased entropy of unfolding. This work gives an initial insight into the effect of conserved proline residues in thermostable chitinases and proposes a feasible approach for improving chitinase thermostability to facilitate its application in chitin hydrolysis to valuable oligosaccharides.

A critical review of cast-off crab shell recycling from the perspective of functional and versatile biomaterials

Shellfish cultivation is an expanding economic activity worldwide. However, the rapid development of crab farming and processing result in a large number of crab shells (CS). Utilizing CS could not only benefit the environment and economy but also promote the sustainable development of aquaculture. In this work, it reviews and analyzes recent attempts in CS recycling, including extracting chitin and its derivatives, for use as adsorbent and flocculant and for preparing polymer composites and catalysts, as well as medical applications. The challenges in these utilizations are discussed, and future research directions are proposed as well. Extracting chitin and its derivates, for use as adsorbent and flocculant, are recent major recycling approaches. Preparing polymer composites and carbon materials has gained more and more attentions. Biotechnology is an alternative method for extracting chitin and its derivates from CS, and high-efficiency desalted and deproteinized bacteria need to be screened. Immobilizing the CS-based adsorbents is the key of treating wastewater in continuous systems. Using CS as a biofiller to prepare polymer composites is promising, and surface modification to improve the interfacial compatibility between CS-based fillers and matrix needs to be further studied.

Effects of chitosan-supplemented diets on the growth performance, nonspecific immunity and health of loach fish (Misgurnus anguillicadatus)

This study investigated the effects of dietary chitosan on the growth performance and nonspecific immunity of loaches (Misgurnus anguillicadatus). Four practical diets at three levels of chitosan (1, 5 and 10 g/kg) were fed to loach (3.13 ± 0.02 g) in triplicate groups (20 fish per replicate) for 10 weeks. Contrary to high-chitosan treatment, the administration of low or moderate levels of oral chitosan (1 or 5 g/kg) significantly increased the body weight gain, specific growth rate and condition factor. The oral administration of chitosan significantly increased the survival rate, phenoloxidase, superoxide dismutase, glutathione peroxidase, lysozyme, acid phosphatase and alkaline phosphatase activities, as well as the immunoglobulin M and complement 3 contents and the disease resistance against Aeromonas hydrophila. The optimum dose of dietary chitosan required for the maximum growth of loach was 5 g/kg. These results indicated that chitosan exerted immunostimulatory effects on loaches (M. anguillicadatus) and can thus be used as a dietary supplement.

Activation and conformational changes of chitinase induced by ultrasound

This study investigated the effect of ultrasound on chitinase activity and conformational changes. Results revealed that ultrasound activated chitinase with a maximum enhancement of 19.17% compared with the untreated chitinase. Furthermore, an increase of V_max and a decrease of K_m after sonication were obtained, illustrating that the affinity between chitinase and substrate was intensified. No obvious effect on the tolerance to most metal ions was exhibited whether sonicated or not (p > 0.05). The conformational changes of chitinase were analyzed by circular dichroism (CD), Fourier transform infrared (FTIR), Raman and fluorescence spectroscopy. Results indicated that the activation of chitinase induced by ultrasound was presumably due to the decrease of tryptophan on the chitinase surface and the increase of β-sheet and random coil in chitinase secondary conformation. In brief, ultrasound is a possible way to activate chitinase to increase its application in food industry.

Isolation and identification of marine strains of Stenotrophomona maltophilia with high chitinolytic activity

Chitin is the second most abundant organic compound in nature and represents a rich carbon and nitrogen source that is primarily transformed by bacterial communities. Bacteria capable of gradually hydrolyzing chitin into N-acetylglucosamine monomers can have applications in the transformation of residues from shrimp and other crustaceans. The objective of the present study was to isolate, characterize and identify microorganisms with high chitinolytic activity. These microorganisms were isolated and characterized based on macro- and microscopic morphological traits. Strains were selected on colloidal chitin agar medium primarily based on a hydrolysis halo larger than 2 mm and a growing phase no longer than 6 days. Secondary selection consisted of semi-quantitative evaluation of chitinolytic activity with a drop dilution assay. From the above, ten strains were selected. Then, strain-specific activity was evaluated. The B4 strain showed the highest specific activity, which was 6,677.07 U/mg protein. Molecular identification indicated that the isolated strains belong to the species Stenotrophomonas maltophilia.

Chitinase: diversity, limitations, and trends in engineering for suitable applications

Chitinases catalyze the degradation of chitin, a ubiquitous polymer generated from the cell walls of fungi, shells of crustaceans, and cuticles of insects. They are gaining increasing attention in medicine, agriculture, food and drug industries, and environmental management. Their roles in the degradation of chitin for the production of industrially useful products and in the control of fungal pathogens and insect pests render them attractive for such purposes. However, chitinases have diverse sources, characteristics, and mechanisms of action that seem to restrain optimization procedures and render standardization techniques for enhanced practical applications complex. Hence, results of laboratory trials are not usually consistent with real-life applications. With the growing field of protein engineering, these complexities can be overcome by modifying or redesigning chitinases to enhance specific features required for specific applications. In this review, the variations in features and mechanisms of chitinases that limit their exploitation in biotechnological applications are compiled. Recent attempts to engineer chitinases for improved efficiency are also highlighted.

Levofloxacin is phytotoxic and modifies the protein profile of lupin seedlings

The toxicity of levofloxacin to yellow lupin plants was evaluated in this study. Recommended indexes of plant (roots and shoots) growth were determined and new indexes were proposed which better characterise the phytotoxicity of levofloxacin. These were, in particular, the activity of antioxidative enzymes, the content of free radicals, as well as the root protein content and the root protein profile. The results showed that levofloxacin considerably affected EC₅₀, measured as the activity of catalase in roots, and leaves (1.05 and 0.069 mM, respectively). The activity of peroxidase in the roots and the dry weight of seedlings were the least sensitive parameters (EC₅₀ was 1.8 and 1.76 mM, respectively). Units of toxicity clearly showed that the activity of catalase is a better measure of toxicity for low concentrations of the drug, and it is a better index of plant physiological state than the morphological parameters of seedlings. Moreover, levofloxacin changed the location of free radicals and the protein profile in plants. The changes in location of reactive oxygen species in roots were an important symptom of the drug toxicity to lupin seedlings. Our results have shown that the toxicity of levofloxacin was manifested mainly by changes in the protein profile. The content of the glyceraldehyde-3-phosphate dehydrogenase, 14-3-3-like protein A, expansin-B3-like precursor, fructose-bisphosphate aldolase, lipoxygenase, nucleotide-binding subunit of vacuolar ATPase and pyruvate dehydrogenase were found to decrease. On the other hand, plant exposure to levofloxacin resulted in an increase in the content of enolase, protein LlR18A, class III chitinase, ascorbate peroxidase, aspartate aminotransferase, alcohol dehydrogenase 1, leghemoglobin reductase-like 17 and heat shock cognate protein 80-like.

Purification, physicochemical and thermodynamic studies of antifungal chitinase with production of bioactive chitosan-oligosaccharide from newly isolated Aspergillus griseoaurantiacus KX010988

In our search for chitinase and chitosanase producer from unconventional sources, the marine-derived fungus Aspergillus griseoaurantiacus KX010988 was obviously the best producer of the highest chitinase and chitosanase activities by solid state fermentation of potato shells. Chitinase was purified in three steps involving ammonium sulphate precipitation, DEAE-cellulose ion-exchange chromatography and Sephacryl S-300 gel chromatography. 12.55 fold increase in purity with a recovery of 17.6 was obtained. The molecular mass of the purified chitinase was found to be 130kDa. It was optimally active at pH 4.5 and 40°C. K_m and V_max values were 0.22mgmL^-1 and 19.6μmolemin^-1mg^-1 respectively. Mn²⁺ and Zn²⁺ ions lead to increased chitinase activity. While Fe²⁺and Cu²⁺ions strongly inhibited the chitinase activity. The thermodynamics of pure chitinase including activation energy for thermal denaturation (E_a,d), change of free energy (ΔG_d), enthalpy(ΔH_d), entropy(ΔS_d) and half life values (T_1/2) at 40, 50 and 60°C were determined. Chitinase showed antifungal activity against pathogenic fungus Fusarium solani. Chitosanase was partially purified by acetone precipitation (50-75%) v/v concentration. The hydrolytic products of moderate molecular weight of chitosan by chitosanase were analyzed by thin layer chromatography (TLC) after 12 and 24h respectively. Chitosan-oligosaccharides showed good antibacterial and antioxidant activities.

Chitin and chitosan preparation from shrimp shells Penaeus monodon and its human ovarian cancer cell line, PA-1

In the present study, chitin and chitosan preparation from shrimp shells Penaeus mondon and its ovarian cancer cell line (PA-1). FTIR spectrum sharp absorption peak at 1655cm^-1 is assigned to ketone C=O (α) unsaturated with chitosan. X-ray diffraction showed the presence of chitin and chitosan were strongest peak at 18.91° (β) and 29.75° (α) characters. SEM observations of chitin and chitosan surface morphologies of P. monodon showed that microfibril and porous structures. Anticancer activity of chitin and chitosan against human ovarian cancer cell line showed that chitosan an exhibited notable higher activity than chitin. Anticancer activity of aquacultural waste of shrimp shells mediated chitosan, which was proved to be good novel pharmaceutical industries.

Biochemical characterization of a novel thermostable chitinase from Hydrogenophilus hirschii strain KB-DZ44

An extracellular acido-thermostable endo-chitinase (called ChiA-Hh59) from thermophilic Hydrogenophilus hirschii strain KB-DZ44, was purified and characterized. The maximum chitinase activity recorded after 36-h of incubation at 60°C was 3000U/ml. Pure enzyme was obtained after heat and acidic treatment, precipitation by ammonium sulphate and acetone, respectively, followed by sequential column chromatographies on Sephacryl S-200 and Mono Q-Sepharose. Based on Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis, the purified enzyme is a monomer with a molecular mass of 59103.12-Da. The 22 residue NH₂-terminal sequence of the enzyme showed high homology with family-18 bacterial chitinases. The optimum pH and temperature values for chitinase activity were pH 5.0 and 85°C, respectively. The pure enzyme was completely inhibited by p-chloromercuribenzoic acid (p-CMB) and N-ethylmaleimide (NEM). The obtained results suggest that ChiA-Hh59 might be an endo-chitinase. The studied chitinase exhibited high activity towards colloidal chitin, chitin azure, glycol chitin, while it did not hydrolyse chitibiose and amylose. Its K_m and k_cat values were 0.298mg colloidal chitin/ml and 14400s^-1, respectively. Its catalytic efficiency was higher than those of chitodextrinase and ChiA-65. Additionally, Thin-layer chromatography (TLC) analysis from chitin-oligosaccharides showed that ChiA-Hh59 acted as an endo-splitting enzyme. In conclusion, this chitinase may have great potential for the enzymatic degradation of chitin.

Production of chitinase from thermophilic Humicola grisea and its application in production of bioactive chitooligosaccharides

A novel thermophilic chitinase producing strain Humicola grisea ITCC 10,360.16 was isolated from soil of semi-arid desert region of Rajasthan. Maximum enzyme production (116±3.45Ul^-1) was achieved in submerged fermentation. Nutritional requirement for maximum production of chitinase under submerged condition was optimized using response surface methodology. Among the eight nutritional elements studied, chitin, colloidal chitin, KCl and yeast-extract were identified as the most critical variables for chitinase production by Plackett-Burman design first. Further optimization of these variables was done by four-factor central composite design. The model came out to be significant and statistical analysis of results showed that an appropriate ratio of chitin and colloidal chitin had resulted into enhancement in enzyme production levels. Optimum concentration of the variables for enhanced chitinase production were 7.49, 4.91, 0.19 and 5.50 (gl^-1) for chitin, colloidal chitin, KCl and yeast extract, respectively. 1.43 fold enhancement in chitinase titres was attained in shake flasks, when the variables were used at their optimum levels. Thin layer chromatography revealed that enzyme can effectively hydrolyze colloidal chitin to produce chitooligosaccharides. Chitinase production from H. grisea and optimization of economic production medium heighten the employment of enzyme for large scale production of bioactive chitooligosaccharides.

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.

Purification, characterization and application of dual coagulants containing chitosan and different Al species in coagulation and ultrafiltration process

The objective of this study was to investigate the effect of different Al species and chitosan (CS) dosages on coagulation performance, floc characteristics (floc sizes, strength and regrowth ability and fractal dimension) and membrane resistance in a coagulation-ultrafiltration hybrid process. Results showed that different Al species combined with humic acid in diverse ways. Al_a had better removal efficiency, as determined by UV₂₅₄ and dissolved organic carbon, which could be further improved by the addition of CS. In addition, the optimal dosage of different Al species was determined to be 4.0mg/L with the CS concentration of 1.0mg/L, by orthogonal coagulation experiments. Combining Al_a/Al_b/Al_c with CS resulted in larger flocs, higher recovery, and higher fractal dimension values corresponding to denser flocs; in particular, the floc size at the steady state stage was four times larger than that obtained with Al species coagulants alone. The results of ultrafiltration experiments indicated that the external fouling percentage was significantly higher than that of internal fouling, at around 85% and 15%, respectively. In addition, the total membrane resistance was significantly decreased due to CS addition.

Competitive adsorption of toxic metals on bentonite and use of chitosan as flocculent coagulant to speed up the settling of generated clay suspensions

Evaluation of modified Algerian clay as mineral adsorbent was done for its adsorbing capacity on copper (Cu) and Zinc (Zn) cations. The results obtained show a rapid kinetic adsorption for both metals (less than 2 h) following the pseudo-second order model with high elimination rates of 67.2 and 61.8% for Cu and Zn respectively. The adsorption isotherms analyzed with Langmuir model revealed a correlation with the experimental values. While the use of obtained chitosan at room temperature, as flocculent coagulant, accelerates the decantation of the colloidal particles in suspension generated after adsorption process.

Enhancement of Exochitinase Production by Bacillus licheniformis AT6 Strain and Improvement of N-Acetylglucosamine Production

A strain producing chitinase, isolated from potato stem tissue, was identified as Bacillus licheniformis by biochemical properties and 16S RNA sequence analysis. Statistical experimental designs were used to optimize nine independent variables for chitinase production by B. licheniformis AT6 strain in submerged fermentation. Using Plackett-Burman design, (NH₄)₂SO₄, MgSO₄.7H₂O, colloidal chitin, MnCl₂ 2H₂O, and temperature were found to influence chitinase production significantly. According to Box-Behnken response surface methodology, the optimal fermentation conditions allowing maximum chitinase production were (in gram per liter): (NH₄)₂SO₄, 7; K₂HPO₄, 1; NaCl, 1; MgSO₄.7H₂O, 0.1; yeast extract, 0.5; colloidal chitin, 7.5; MnCl₂.2H₂O, 0.2; temperature 35 °C; pH medium 7. The optimization strategy led to a 10-fold increase in chitinase activity (505.26 ± 22.223 mU/mL versus 50.35 ± 19.62 mU/mL for control basal medium). A major protein band with a molecular weight of 61.9 kDa corresponding to chitinase activity was clearly detected under optimized conditions. Chitinase activity produced in optimized medium mainly releases N-acetyl glucosamine (GlcNAc) monomer from colloidal chitin. This enzyme also acts as an exochitinase with β-N-acetylglucosaminidase. These results suggest that B. licheniformis AT6 secreting exochitinase is highly efficient in GlcNAc production which could in turn be envisaged as a therapeutic agent or as a conservator against the alteration of several ailments.

Optimization of chitin yield from shrimp shell waste by Bacillus subtilis and impact of gamma irradiation on production of low molecular weight chitosan

Chitin and chitosan have been produced from the exoskeletons of crustacean shells such as shrimps. In this study, seventy bacterial isolates, isolated from soil, were tested for proteolytic enzymes production. The most efficient one, identified as Bacillus subtilis, was employed to extract chitin from shrimp shell waste (SSW). Following one-variable-at-a-time approach, the relevant factors affecting deproteinization (DP) and demineralization (DM) were sucrose concentration (10%, w/v), SSW concentration (5%, w/v), inoculum size (15%, v/v), and fermentation time (6days). These factors were optimized subsequently using Box-Behnken design and response surface methodology. Maximum DP (97.65%) and DM (82.94%) were predicted at sucrose concentration (5%), SSW concentration (12.5%), inoculum size (10%, containing 35×10(8) CFU/mL), and fermentation time (7days). The predicted optimum values were verified by additional experiment. The values of DP (96.0%) and DM (82.1%) obtained experimentally correlated to the predicted values which justify the authenticity of optimum points. Overall 1.3-fold increase in DP% and DM% was obtained compared with 75.27% and 63.50%, respectively, before optimization. Gamma-irradiation (35kGy) reduced deacetylation time of irradiated chitin by 4.5-fold compared with non-irradiated chitin. The molecular weight of chitosan was decreased from 1.9×10(6) (non-irradiated) to 3.7×10(4)g/mol (at 35kGy).

Heterologous expression and characterization of two chitinase 5 enzymes from the migratory locust Locusta migratoria

Insect chitinases are involved in degradation of chitin from the exoskeleton or peritrophic metrix of midgut. In Locusta migratoria, two duplicated Cht5s (LmCht5-1 and LmCht5-2) have been shown to have distinct molecular characteristics and biological roles. To explore the protein properties of the two LmCht5s, we heterologously expressed both enzymes using baculovirus expression system in SF9 cells, and characterized kinetic and carbohydrate-binding properties of purified enzymes. LmCht5-1 and LmCht5-2 exhibited similar pH and temperature optimums. LmCht5-1 has lower Km value for the oligomeric substrate (4MU-(GlcNAc)3 ), and higher Km value for the longer substrate (CM-Chitin-RBV) compared with LmCht5-2. A comparison of amino acids and homology modeling of catalytic domain presented similar TIM barrel structures and differentiated amino acids between two proteins. LmCht5-1 has a chitin-binding domain (CBD) tightly bound to colloidal chitin, but LmCht5-2 does not have a CBD for binding to colloidal chitin. Our results suggested both LmCht5-1 and LmCht5-2, which have the critical glutamate residue in region II of catalytic domain, exhibited chitinolytic activity cleaving both polymeric and oligomeric substrates. LmCht5-1 had relatively higher activity against the oligomeric substrate, 4MU-(GlcNAc)3 , whereas LmCht5-2 exhibited higher activity toward the longer substrate, CM-Chitin-RBV. These findings are helpful for further research to clarify their different roles in insect growth and development.

Cloning, Expression and 3D Structure Prediction of Chitinase from Chitinolyticbacter meiyuanensis SYBC-H1

Two CHI genes from Chitinolyticbactermeiyuanensis SYBC-H1 encoding chitinases were identified and their protein 3D structures were predicted. According to the amino acid sequence alignment, CHI1 gene encoding 166 aa had a structural domain similar to the GH18 type II chitinase, and CHI2 gene encoding 383 aa had the same catalytic domain as the glycoside hydrolase family 19 chitinase. In this study, CHI2 chitinase were expressed in Escherichia coli BL21 cells, and this protein was purified by ammonium sulfate precipitation, DEAE-cellulose, and Sephadex G-100 chromatography. Optimal activity of CHI2 chitinase occurred at a temperature of 40 °C and a pH of 6.5. The presence of metal ions Fe³⁺, Fe²⁺, and Zn²⁺ inhibited CHI2 chitinase activity, while Na⁺ and K⁺ promoted its activity. Furthermore, the presence of EGTA, EDTA, and β-mercaptoethanol significantly increased the stability of CHI2 chitinase. The CHI2 chitinase was active with p-NP-GlcNAc, with the K_m and V_m values of 23.0 µmol/L and 9.1 mM/min at a temperature of 37 °C, respectively. Additionally, the CHI2 chitinase was characterized as an N-acetyl glucosaminidase based on the hydrolysate from chitin. Overall, our results demonstrated CHI2 chitinase with remarkable biochemical properties is suitable for bioconversion of chitin waste.

Characterization of Thermotolerant Chitinases Encoded by a Brevibacillus laterosporus Strain Isolated from a Suburban Wetland

To isolate and characterize chitinases that can be applied with practical advantages, 57 isolates of chitin-degrading bacteria were isolated from the soil of a suburban wetland. 16S rRNA gene analysis revealed that the majority of these strains belonged to two genera, Paenibacillus and Brevibacillus. Taking thermostability into account, the chitinases (ChiA and ChiC) of a B. laterosporus strain were studied further. Ni-NTA affinity-purified ChiA and ChiC were optimally active at pH 7.0 and 6.0, respectively, and showed high temperature stability up to 55 °C. Kinetic analysis revealed that ChiC has a lower affinity and stronger catalytic activity toward colloidal chitin than ChiA. With their stability in a broad temperature range, ChiA and ChiC can be utilized for the industrial bioconversion of chitin wastes into biologically active products.

Effects of chitin and its derivatives on human cancer cells lines

The present study is focused on the effect of chitin derivatives against human cancer cell lines RD and Hep2. As an outcome from this research, chitin was cytotoxic at IC50 = 400 μg/ml and 200 μg/ml against Hep2 cells and RD cells lines, respectively. Irradiated chitin had an IC50 value of 450 μg/ml for Hep2 and an IC50 of 200 μg/ml for RD. The lowest IC50 is attributed to chitosan, 300 μg/ml in Hep2 and 190 μg/ml in RD.