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The whole enzymatic conversion of chitin is a green and promising alternative to current strategies, which are based on lytic polysaccharide monooxygenases (LPMOs) and chitinases. However, the lack of LPMOs with high activity toward α-chitin limits the efficient bioconversion of α-chitin. Herein, we characterized a high chitin-active LPMO from Oceanobacillus sp. J11TS1 ( Os LPMO10A), which could promote the decrystallization of the α-chitin surface. Furthermore, when coupled with Os LPMO10A, the conversion rate of α-chitin to N -acetyl chitobiose [(GlcNAc) 2 ] by three chitinases ( Serratia marcescens , ChiA, -B, and -C) reached 30.86%, which was 2.03-folds that without the addition of Os LPMO10A. Moreover, the results of synergistic reactions indicated that Os LPMO10A and chitinases promoted the degradation of α-chitin each other mainly on the surface. To the best of our knowledge, this study achieved the highest yield of N -acetyl chitooligosaccharides ( N -acetyl COSs) among reported LPMOs-driven bioconversion systems, which could be regarded as a promising candidate for α-chitin bioconversion.

In this study, a novel magnetic macroporous chitin microsphere (MMCM) was developed for enzyme immobilization. Chitin nanofibers were prepared and subsequently subjected to self-assembly with magnetic nanoparticles and PMMA (polymethyl methacrylate). Following this, microspheres were formed through spray drying, achieving a porous structure through etching. The MMCM serves as an effective support for immobilizing enzymes, allowing for their covalent immobilization both on the microsphere's surface and within its pores. The substantial surface area resulting from the porous structure leads to a 2.1-fold increase in enzyme loading capacity compared to non-porous microspheres. The MMCM enhances stability of the immobilized enzymes under various pH and temperature conditions. Furthermore, after 20 days of storage at 4 °C, the residual activity of the immobilized enzyme was 2.93 times that of the free enzyme. Even after being recycled 10 times, the immobilized enzyme retained 56.7 % of its initial activity. It's noteworthy that the active sites of the enzymes remained unchanged after immobilization using the MMCM, and kinetic analysis revealed that the affinity of the immobilized enzymes rivals that of the free enzymes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence he work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Development of a high-performance chitinase for efficient biotransformation of insoluble chitinous substrate would be highly valuable in industry. In this study, the chitin-binding domains (ChBDs) of chitinase SaChiA4 were successfully modified to improve the enzymatic activity. The engineered substitution variant R-SaChiA4, which had the exogenous ChBD of chitinase ChiA1 from Bacillus circulans WL-12 (ChBD ChiA1 ) substituted for its original ChBD ChiA4 , increased its activity by nearly 54% (28.0 U/mg) towards chitin powder, and by 49% towards colloidal chitin, compared with the wild-type. The substrate-binding assay demonstrated that the ChBD could enhance the capacity of enzymatic hydrolysis by promoting substrate affinity, and molecular dynamics simulations indicated that this could be due to hydrophobic interactions in different substrate binding modes. This work advances the understanding of the role of the ChBD, and provides a step towards the achievement of industrial-scale hydrolysis and utilization of insoluble chitin., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Natural deep eutectic solvents (NADESs) are sustainable, nontoxic, and biodegradable solvents, which are composed of natural primary metabolites. A green and efficient approach based on choline chloride-malic acid, a NADES, was developed for extracting chitin from crustacean shells, and its effectiveness for demineralization and deproteinization was determined. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to investigate changes in the chemical composition of extracted chitin. The results revealed that most of the minerals and proteins were removed from the shrimp shells by using a NADES with the assistance of microwave irradiation. The quality of the obtained chitin was superior, and it displayed a relative crystallinity of 71%. All of these results were achieved without using harsh chemicals, which can raise environmental issues. This study provides a green and facile approach for chitin production from crustacean shells and reveals the potential of NADESs for applications in the extraction of biopolymers from natural sources.

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

Shrimp has constituted a major part of crustacean consumption in recent years. Solid wastes, including the head, shell, and tail portions, accumulate owing to shrimp processing. The accumulated biowastes without appropriate utilization have resulted in a squander of sources and problems of waste disposal and environmental pollution. Proper shrimp waste processing is an approach to recover biomaterials such as chitin, protein, lipids, astaxanthin, flavor compounds, and calcium carbonate. These active components have large-scale applications in biology as well as in food, pharmaceutical, agricultural, cosmetic, pulp, and textile industries. Traditionally, methods applied for the utilization of shrimp waste are chemical procedures using corrosive or hazardous reagents (such as HCl and NaOH), which are known to cause environmental pollution and resource wastage (or incomprehensive utilization) and increase the associated costs. However, new environment-friendly and clean technologies are emerging. In this review, we briefly analyze the bioactive compounds recovered from shrimp waste. A concise overview of the comprehensive utilization of shrimp waste in recent years has been included. Biotechnological methods such as biocatalysis and biotransformation with enzymes and microorganisms have also been described. The rapid development of corresponding biotechnology enables a simple, fast, effective, clean, economic, and controllable bioprocess for the comprehensive utilization of crustacean waste. [ABSTRACT FROM AUTHOR]

In this research, a two-step extraction approach was developed for chitin preparation from shrimp shells by utilizing citric acids and deep eutectic solvents (DESs), which effectively removed minerals and proteins. In the first step, minerals of shrimp shells were removed by citric acid, and the demineralization efficiency reached more than 98%. In the second step, the removal of protein was carried out using deep eutectic solvents with the assistance of microwave, and the deproteinization efficiency was more than 88%. The results of scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), and thermogravimetric analysis (TGA) showed that the quality of DES-prepared chitin was comparable to that of traditional acid/alkali-prepared chitin. These results were realized without utilizing hazardous chemicals, which are detrimental to the environment. This research indicates that a DES-based preparation approach has the potential for application in the recovery of biopolymers from natural resources. [ABSTRACT FROM AUTHOR]

Many by-products that are harmful to the environment and human health are generated during food processing. However, these wastes are often potential resources with high-added value. For example, crustacean waste contains large amounts of chitin. Chitin is one of the most abundant polysaccharides in natural macromolecules, and is a typical component of crustaceans, mollusks, insect exoskeleton and fungal cell walls. Chitosan is prepared by deacetylation of chitin and a copolymer of D-glucosamine and N -acetyl-D-glucosamine through β-(1 → 4)-glycosidic bonds. Chitosan has better solubility, biocompatibility and degradability compared with chitin. This review introduces the preparation, physicochemical properties, chemical and physical modification methods of chitosan, which could help us understand its biological activities and applications. According to the latest reports, the antibacterial activity, antioxidant, immune and antitumor activities of chitosan and its derivatives are summarized. Simultaneously, the various applications of chitosan and its derivatives are reviewed, including food, chemical, textile, medical and health, and functional materials. Finally, some insights into its future potential are provided, including novel modification methods, directional modification according to structure-activity relationship, activity and application development direction, etc. • The utilization of chitosan is effective solution to improve the value of waste. • The physicochemical properties and modification of chitosan were reviewed. • Chitosan and its derivatives have many biological activities. • Chitosan and its derivatives can be used in various industrial fields. [ABSTRACT FROM AUTHOR]

In this study, carboxymethylation and TEMPO-mediated oxidation were compared for their ability to introduce carboxyl groups to polysaccharides, using cellulose and chitin as model polysaccharides. The carboxyl group contents and changes in the molecular weight of carboxymethylated and TEMPO-oxidized cellulose/chitin were measured. The results revealed that carboxymethylation achieved higher carboxyl group contents, with values of 4.99 mmol/g for cellulose and 4.46 mmol/g for chitin, whereas for TEMPO-oxidized cellulose and chitin, the values were 1.64 mmol/g and 1.12 mmol/g, respectively. As a consequence of TEMPO-mediated oxidation, polysaccharides underwent degradation, leading to a decrease in the molecular weight of 42.46 % for oxidized cellulose and 64.5 % for oxidized chitin. Additionally, the crystallinity of carboxymethylated polysaccharides decreased with an increase in the carboxyl group contents, whereas that of TEMPO-oxidized polysaccharides remained unchanged. Furthermore, TEMPO-mediated oxidation selectively oxidized C6 primary hydroxyls, while carboxylmethylation converted all the hydroxyl groups on the polysaccharides. [ABSTRACT FROM AUTHOR]

Highlights • Chitin was pretreated with ionic liquid (IL). • IL-chitin was used as substrate for chitinase from S. albolongus. • The enzymatic hydrolysis yields from different pretreated chitin were compared. • The influence of chitin structure on its enzymatic hydrolysis was investigated. • The dissolution mechanism of chitin in IL was studied by NMR spectroscopic. Abstract Colloidal chitin, the substrate of chitinase with an open hydrated gel-like structure, can be obtained by treatment using either traditional hydrochloric acid (HCl) or ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). IL-pretreated chitin provided an efficient production of N-acetylglucosamine (175.62 mg g chitin) and N , N '-diacetylchitobiose (341.70 mg g chitin) with a conversion of 61.49% at 48 h catalyzed by chitinase from Streptomyces albolongus ATCC 27414. A short time second homogenization treatment after IL pretreatment can increase the conversion to 76.11%. A comprehensive characterization and comparison of chitin with different pretreatments suggested that enzymatic performances were correlated with the structural changes (size of the grains and porosity), high decrease in crystallinity, and high enzyme adsorption. The NMR spectroscopy studies of N-acetylglucosamine solvation in [Emim][OAc] clearly suggest that hydrogen bonding is formed between the hydroxyls of N-acetylglucosamine and both the anions and cations of the IL. [ABSTRACT FROM AUTHOR]

Shrimp processing and consumption generate each year thousand tons of wastes, which are the sources of raw material for the production of chitin. Successive cofermentation was applied to biologically extract chitin from shrimp head waste in combination with a protease-producing bacterium, Bacillus licheniformis 21886 ( B. 21886), and an acid-producing bacterium, Gluconobacter oxydans DSM-2003 ( G. 2003). When they were cultivated individually, B. 21886 removed 83.1% of the protein in the absence of glucose and G. 2003 95% of minerals from shrimp heads. When the waste was first cofermented with B. 21886 followed by G. 2003, the deproteinization (DP) and demineralization (DM) efficiencies were 87 and 93.5% respectively at a chitin content of 90.8%. In the cofermentation broth eight organic acids with a total amount of 16 g/l were found. Major acids were lactic, formic and acetic acid, followed by gluconic, succinic, pyroglutaminc and propionic acid. In the cofermenation, three times more organic acids were released than in the monofermentation of G. 2003. The fermentation time of 96 h was almost half of the cultivated cycle reported. [ABSTRACT FROM AUTHOR]

• Two novel GlcNAcases (SvNag2557 and SvNag4755) were identified and characterized. • SvNag2557 and SvNag4755 displayed an exo-type cleavage pattern. • SvNag2557 exhibited higher hydrolytic efficiency for (GlcNAc) 2. • A one-pot bioprocess for pure GlcNAc production was developed. Chitin, one of the most abundant renewable biopolymers on Earth, is commercially available from crustacean wastes. One critical step in converting chitin to high-value products is its degradation by chitinolytic enzymes to N -acetyl- d -glucosamine (GlcNAc), which plays a significant role in functional food and pharmaceutical industries. Here, we cloned and biochemically characterized two novel β - N -acetylglucosaminidases named SvNag2557 (family-84) and SvNag4755 (family-3) from Streptomyces violascens ATCC 27968. Both SvNag2557 and SvNag4755 exhibited strict substrate specificity toward N -acetyl chitooligosaccharides with GlcNAc as the sole product. Thus, a one-pot production for pure GlcNAc from chitin by an enzyme cocktail reaction was further developed. Under the co-action of an endo-type chitinase SaChiA4 and SvNag2557 (mass ratio 1:2), the final conversion rates of colloidal chitin and ionic liquid pretreated chitin to GlcNAc were 80.2% and 73.8% with GlcNAc purities of 99.7% and 96.8%, respectively. [ABSTRACT FROM AUTHOR]

The present study aimed to discuss the applicability of a clean fermentation-organic acid method for various sources of shrimp waste (shrimp head and shell). Six major cultivated shrimp species in China, including Penaeus vannamei , Penaeus monodon , Fenneropenaeus chinensis , Penaeus japonicus , Macrobrachium rosenbergii , and Procambarus clarkii , were selected as the sources of shrimp waste. The numerical ranges of the corresponding characteristic biochemical indicators were as follows: moisture, 69.47%–79.44%; ash, 21.01%–39.11%; crude protein, 29.65%–46.04%; and crude lipid, 3.18%–9.64%; the data indicated that these types of shrimp waste were good sources for the extraction of chitin, protein and elemental calcium. The traditional chemical method and fermentation-organic acid method were used, and the results of processing the shrimp waste were compared. The results indicated that the purity of the chitin extracted by the fermentation-organic method was as good as the purity of the extracted by the chemical method. Moreover, chitin extracted by the fermentation-organic method had lower acetylation rate, crystallinity index and thermal stability compared with that of chitin extracted by the chemical method. These characteristics indicate that chitin extracted by the fermentation-organic method could be easily deacetylated or degraded leading to easier production of chitin derivatives, such as chitosan or chitooligosaccharides, from this type of chitin. Protein and calcium could be efficiently recycled during the chitin extraction process producing high nutrition protein raw material and high purity calcium citrate. These results suggest a cleaner method for the treatment of the shrimp waste generated from the major cultivated shrimp species in China. [Display omitted] • Chemical composition of six kinds of shrimp wastes were systematically analyzed. • Chitin extracted by new method has lower acetylation rate, crystallinity and thermal stability. • Protein and calcium could be recycled during chitin extraction process. [ABSTRACT FROM AUTHOR]

• Aptamer 6H5 can recognize His-tag-containing chitinase using color change. • Our method is based on single-strand DNA aptamers and gold nanoparticles. • His-tag-containing chitinase can be detected qualitatively within 5 min. • The proposed method is cheaper than alternatives. Chitooligosaccharides are oligosaccharides with many biological activities that can be used in food production for sweeteners, preservatives and humectants, among other products. Chitin, a long-chain polymer of N -acetylglucosamine and a derivative of glucose, can be hydrolyzed by applying chitinase to break down glycosidic bonds to form chitooligosaccharides. Chitinases arising from heterologous gene expression are usually linked to a 6 × His-tag to facilitate easy purification. Heterologously expressed chitinase linked to a 6 × His-tag is a transgenic element, but enzyme activity tests cannot be used to distinguish transgenic elements from natural elements. In this study, we established a rapid and easy method to detect His-tag-containing chitinase using gold nanoparticles (AuNPs) and ssDNA aptamers. Using this method, His-tag-containing chitinase could be detected at concentrations as low as 0.136 nM within 5 min. Color changes of AuNPs showed a positive correlation with His-tag-containing chitinase concentrations. [ABSTRACT FROM AUTHOR]