Low molecular weight chitosan prepared with the aid of cellulase, lysozyme and chitinase: Characterisation and antibacterial activity

Alternative processes to produce chitin, chitosan, and their oligomers

Sustainable recovery of chitin and its derivatives from shellfish waste will be achieved when the industrial production of these polymers is achieved with a high control of their molecular structure, low costs, and acceptable levels of pollution. Therefore, the conventional chemical method for obtaining these biopolymers needs to be replaced or optimized. The goal of the present review is to ascertain what alternative methods are viable for the industrial-scale production of chitin, chitosan, and their oligomers. Therefore, a detailed review of recent literature was undertaken, focusing on the advantages and disadvantages of each method. The analysis of the existing data allows suggesting that combining conventional, biological, and alternative methods is the most efficient strategy to achieve sustainable production, preventing negative impacts and allowing for the recovery of high added-value compounds from shellfish waste. In conclusion, a new process for obtaining chitinous materials is suggested, with the potential of reducing the consumption of reagents, energy, and water by at least 1/10, 1/4, and 1/3 part with respect to the conventional process, respectively.

Quality and staling characteristics of white bread fortified with lysozyme-hydrolyzed mealworm powder (Tenebrio molitor L.)

Edible insects have a low environmental impact but are rich in nutrients and have been promoted as alternative protein sources. However, adding insect flour to bread negatively affects the overall quality, especially loaf volume and textural properties. Furthermore, relevant studies on chitin are limited. Therefore, this study examined chitin hydrolysis using lysozymes to enhance the quality characteristics in defatted mealworm (Tenebrio molitor L.) powder (DF-M)-supplemented bread. The chitin hydrolysis degree by lysozymes was evaluated using the 3,5-dinitrosalicylic acid assay and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. The amount of chitin oligomers increased with time, and no significant difference in the hydrolysis efficiency between water and 400 mM acetate buffer was observed. Enzymatic hydrolysis improved the DF-M water- and oil-binding and antioxidant capacities. In addition, chitin hydrolysis increased the volume and softened the texture of white bread. In particular, bread supplemented with DF-M hydrolyzed for 4 h at 10 % had the highest moisture content among the mealworm-added bread groups during storage for 5 days. Moreover, sensory evaluation showed a positive effect of chitin hydrolysis on acceptability. Our findings indicate that chitin hydrolysis can improve the quality of bread containing insect additives. In conclusion, this study provides novel insights into producing high-quality and functional bakery products from edible insects by the enzymatic hydrolysis of edible insect powders and could expand the applications of edible insects as food ingredients.

Chitosan: Properties and Its Application in Agriculture in Context of Molecular Weight

Chitosan is a naturally occurring compound that can be obtained from deacetylated chitin, which is obtained from various sources such as fungi, crustaceans, and insects. Commercially, chitosan is produced from crustaceans. Based on the range of its molecular weight, chitosan can be classified into three different types, namely, high molecular weight chitosan (HMWC, >700 kDa), medium molecular weight chitosan (MMWC, 150-700 kDa), and low molecular weight chitosan (LMWC, less than 150 kDa). Chitosan shows several properties that can be applied in horticultural crops, such as plant root growth enhancer, antimicrobial, antifungal, and antiviral activities. Nevertheless, these properties depend on its molecular weight (MW) and acetylation degree (DD). Therefore, this article seeks to extensively review the properties of chitosan applied in the agricultural sector, classifying them in relation to chitosan's MW, and its use as a material for sustainable agriculture.

Prevention of marine biofouling in the aquaculture industry by a coating based on polydimethylsiloxane-chitosan and sodium polyacrylate

In this study, a series of novel hydrophobic/hydrophilic hybrid (HHH) coatings with the feature of preventing the fouling phenomenon was fabricated based on polydimethylsiloxane (PDMS), as matrix and two hydrophilic polymers: chitosan and sodium polyacrylate, as dispersed phases. Antibacterial activity, pseudo-barnacle adhesion strength, surface free energy, water contact angle, and water absorption were performed for all samples. Evaluating field immersion of the samples was performed in the natural seawater. The results showed that the dispersed phase containing PDMS coatings showed simultaneously both of antibacterial activity and foul release behavior. Among the samples, the PCs4 coating containing 4 wt% Cs indicated the lowest pseudo barnacle adhesion strength (0.04 MPa), the lowest surface free energy (18.94 mN/m), the highest water contact angle (116.05°), and the percentage of fouling organisms 9.8 % after 30 days immersion. The HHH coatings can be considered as novel eco-friendly antifouling/foul release coatings for aquaculture applications.

Crude Enzyme Concentrate of Filamentous Fungus Hydrolyzed Chitosan to Obtain Oligomers of Different Sizes

Chitosan is a non-cytotoxic polysaccharide that, upon hydrolysis, releases oligomers of different sizes that may have antioxidant, antimicrobial activity and the inhibition of cancer cell growth, among other applications. It is, therefore, a hydrolysis process with great biotechnological relevance. Thus, this study aims to use a crude enzyme concentrate (C_EC) produced by a filamentous fungus to obtain oligomers with different molecular weights. The microorganism was cultivated in a liquid medium (modified Czapeck-with carboxymethylcellulose as enzyme inducer). The enzymes present in the C_EC were identified by LC-MS/MS, with an emphasis on cellobiohydrolase (E.C 3.2.1.91). The fungus of the Aspergillus genus was identified by amplifying the ITS1-5.8S-ITS2 rDNA region and metaproteomic analysis, where the excreted enzymes were identified with sequence coverage greater than 84% to A. nidulans. Chitosan hydrolysis assays compared the C_EC with the commercial enzyme (Celluclast 1.5 L^®). The ability to reduce the initial molecular mass of chitosan by 47.80, 75.24, and 93.26% after 2.0, 5.0, and 24 h of reaction, respectively, was observed. FTIR analyses revealed lower absorbance of chitosan oligomers' spectral signals, and their crystallinity was reduced after 3 h of hydrolysis. Based on these results, we can conclude that the crude enzyme concentrate showed a significant technological potential for obtaining chitosan oligomers of different sizes.

Homogeneous preparation of water-soluble products from chitin under alkaline conditions and their cell proliferation in vitro

The purpose of this study was to prepare water-soluble products by homogeneous depolymerization of chitin with H₂O₂ under alkaline conditions and investigate their potential application in wound healing. For the first time, water-soluble products were successfully prepared using a chitin-NaOH/urea solution; the products were chitosans with molecular weights (Mw) of 3.48-33.5 kDa and degrees of deacetylation (DD) > 0.5. Their Mw, DD and yield were affected by the reaction temperature, reaction time, concentration of H₂O₂ and chitin DD. The deacetylation and depolymerization of chitin were achieved simultaneously. The depolymerization of chitin was caused by hydrogen abstraction of HO, whereas the deacetylation resulted from the cleavage of amide bonds by HO^- and HO₂^-, although the latter played a more important role. All water-soluble chitosans markedly promoted the proliferation of human skin fibroblast (HSF) cells, but they inhibited the proliferation of human keratinocyte cells. For the proliferation of HSF, a low concentration of chitosans was important. In addition, water-soluble chitosans with an Mw of 3.48-16.4 kDa markedly stimulated the expression of growth factors such as PDGF and TGF-β by macrophages. Water-soluble chitosans could be used as a potential active component in wound dressings.

Application of depolymerized chitosan in crop production: A review

Currently, chitosan (CHT) is well known for its uses, particularly in veterinary and agricultural fields. However, chitosan's uses suffer greatly due to its extremely solid crystalline structure, it is insoluble at pH levels above or equal to 7. This has sped up the process of derivatizing and depolymerizing it into low molecular weight chitosan (LMWCHT). As a result of its diverse physicochemical as well as biological features which include antibacterial activity, non-toxicity, and biodegradability, LMWCHT has evolved into new biomaterials with extremely complex functions. The most important physicochemical and biological property is antibacterial, which has some degree of industrialization today. CHT and LMWCHT have potential due to the antibacterial and plant resistance-inducing properties when applied in crop production. This study has highlighted the many advantages of chitosan derivatives as well as the most recent studies on low molecular weight chitosan applications in crop development.

Constitutive chitosanase from Bacillus thuringiensis B-387 and its potential for preparation of antimicrobial chitooligomers

The article proves the ability of the entomopathogenic strain B. thuringiensis var. dendrolimus B-387 to high the constitutive production (3-12.5 U/mL) of extracellular chitosanase, that was found for the first time. The enzyme was purified in 94-fold by ultrafiltration, affinity sorption and cation-exchange chromatography and characterized biochemically. The molecular mass of the chitosanase determined using SDS-PAGE is 40 kDa. Temperature and pH-optima of the enzyme are 55 ^°C and pH 6.5, respectively; the chitosanase was stable under 50-60 ^°C and pH 4-10.5. Purified chitosanase most rapidly (V_max ~ 43 µM/mL × min, K_M ~ 0.22 mg/mL, k_cat ~ 4.79 × 10⁴ s^-1) hydrolyzed soluble chitosan of the deacetylation degree (DD) 85% by endo-mode, and did not degrade colloidal chitin, CM-cellulose and some other glucans. The main reaction products of the chitosan enzymolysis included chitobiose, chitotriose and chitotetraose. In addition to small chitooligosaccharides (CHOs), the studied chitosanase also generated low-molecular weight chitosan (LMWC) with average M_w in range 14-46 kDa and recovery 14-35%, depending on the enzyme/substrate ratio and incubation temperature. In some cases, the chitosan (DD 85 and 50%) oligomers prepared using crude chitosanase from B. thuringiensis B-387 indicated higher antifungal and antibacterial activities in vitro in comparison with the initial polysaccharides. The data obtained indicate the good prospect of chitosanase B-387 for the production of bioactive CHOs.

Diversity and antimicrobial activities of culturable actinomycetes from Odontotermes formosanus (Blattaria: Termitidae)

BACKGROUND

Actinomycetes are important microbes, and they are very important for developing active substances for useful drugs. Actinomycetes are numerous inhabitants, and they are widely distributed in the nest of fungus-growing termites. Previously, we isolated and purified numerous actinomycetes from the combs of Odontotermes formosanus and obtained a variety of valuable natural products.

RESULTS

Here, we isolated and purified actinomycetes from fungus-growing termite Odontotermes formosanus using medium-based cultures. Among the eight media tested, M7 and I-HV media were found suitable for isolating actinomycetes. Further, 84 actinomycetes, including 79 Streptomyces isolates, were isolated and purified from O. formosanus and its combs, which belong to four genera (Streptomyces, Kribbella, Amycolatopsis, and Cellulosimicrobium). Then, the type and quantity of actinomycetes were positively correlated with the activity range of termites. Twenty-two actinomycetes strains showed antimicrobial activities. Among them, the BYF18, BYF48, BYF70, and BYF106 strains exhibited antifungal activities against five pathogenic fungi, with zone of inhibition (ZOI) values ranging from 3 to 21 mm. Grincamycin N was isolated and purified from the metabolites of Streptomyces lannensis (BYF106), and it displayed antibacterial activities against Staphylococcus aureus (ZOI = 13.82 ± 0.52 mm) and Micrococcus tetragenus (ZOI = 17.6 ± 0.5 mm) (gentamycin sulfate, as the positive control, had ZOI values of 19.9 ± 0.5 mm and 30.83 ± 0.75 mm, against S. aureus and M. tetragenus, respectively).

CONCLUSIONS

Our results confirmed that the actinomycetes associated with O. formosanus are important sources of new active substances.

Fabrication of chitosan/alginate/hydroxyapatite hybrid scaffolds using 3D printing and impregnating techniques for potential cartilage regeneration

Three-dimensional (3D) printed hydrogel scaffolds enhanced with ceramics have shown potential applications for cartilage regeneration, but leaving biological and mechanical properties to be desired. This paper presents our study on the development of chitosan /alginate scaffolds with nano hydroxyapatite (nHA) by combining 3D printing and impregnating techniques, forming a hybrid, yet novel, structure of scaffolds for potential cartilage regeneration. First, we incorporated nHA into chitosan scaffold printing and studied the printability by examining the difference between the printed scaffolds and their designs. Then, we impregnated alginate with nHA into the printed chitosan scaffolds to forming a hybrid structure of scaffolds; and then characterized the scaffolds mechanically and biologically, with a focus on identifying the influence of nHA and alginate for potential cartilage regeneration. The results of compression tests on the scaffolds showed that the inclusion of nHA increased the elastic moduli of scaffolds; while the live/dead assay illustrated that nHA had a great effect on improving attachment and viability of ATCD5 cells on the scaffolds. Also, our results illustrated scaffolds with nHA impregnated in alginate hydrogel enhanced the cell viability and attachment. Furthermore, antibacterial activity of hybrid scaffolds was characterized with results indicating that the chitosan scaffolds had favourable antibacterial ability, which was further enhanced with the impregnated nHA. Taken together, our study has illustrated that chitosan/HA/alginate hybrid scaffolds are promising for cartilage regeneration and the methods developed to create hybrid scaffolds based on 3D printing and impregnating techniques, which can also be extended to fabricating scaffolds for other tissue engineering applications.

Preparation, characterization and antimicrobial activities of cyclic substituted chitosan derivatives

Six cyclic substituted chitosan derivatives were synthesized, and their structures were characterized by FTIR, ¹³C NMR and elemental analyses. Additionally, their antimicrobial properties were studied. The synthesized derivatives showed significantly greater zones of inhibition compared with chitosan. The zone of inhibition values produced by C₂-2-naphthylamine formamide-C₆-2-naphthylamine formyl ester-polymer chitosan against Sarcina sp., Staphylococcus aureus and Escherichia coli were 24 mm, 21 mm and 21 mm, respectively, whereas those of C₂-cyclohexylamine formamide-C₆-cyclohexylamine formyl ester-low chitosan against Fusarium equiseti and Verticillium dahliae were 14 mm and 15 mm, respectively. The antibacterial abilities of chitosan and its derivatives against the Gram-positive bacteria Sarcina sp. and Staphylococcus aureus were stronger than those against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. In addition, all of the high and low molecular weight chitosan derivatives showed greater bacteriostatic activities than antifungal activities. The results provided a useful reference for the development of chitosan and its derivatives used as new pesticides.

Innovative Non-Thermal Technologies for Recovery and Valorization of Value-Added Products from Crustacean Processing By-Products-An Opportunity for a Circular Economy Approach

The crustacean processing industry has experienced significant growth over recent decades resulting in the production of a great number of by-products. Crustacean by-products contain several valuable components such as proteins, lipids, and carotenoids, especially astaxanthin and chitin. When isolated, these valuable compounds are characterized by bioactivities such as anti-microbial, antioxidant, and anti-cancer ones, and that could be used as nutraceutical ingredients or additives in the food, pharmaceutical, and cosmetic industries. Different innovative non-thermal technologies have appeared as promising, safe, and efficient tools to recover these valuable compounds. This review aims at providing a summary of the main compounds that can be extracted from crustacean by-products, and of the results obtained by applying the main innovative non-thermal processes for recovering such high-value products. Moreover, from the perspective of the circular economy approach, specific case studies on some current applications of the recovered compounds in the seafood industry are presented. The extraction of valuable components from crustacean by-products, combined with the development of novel technological strategies aimed at their recovery and purification, will allow for important results related to the long-term sustainability of the seafood industry to be obtained. Furthermore, the reuse of extracted components in seafood products is an interesting strategy to increase the value of the seafood sector overall. However, to date, there are limited industrial applications for this promising approach.

Production of Low Molecular Weight Chitosan and Chitooligosaccharides (COS): A Review

Chitosan is a biopolymer with high added value, and its properties are related to its molecular weight. Thus, high molecular weight values provide low solubility of chitosan, presenting limitations in its use. Based on this, several studies have developed different hydrolysis methods to reduce the molecular weight of chitosan. Acid hydrolysis is still the most used method to obtain low molecular weight chitosan and chitooligosaccharides. However, the use of acids can generate environmental impacts. When different methods are combined, gamma radiation and microwave power intensity are the variables that most influence acid hydrolysis. Otherwise, in oxidative hydrolysis with hydrogen peroxide, a long time is the limiting factor. Thus, it was observed that the most efficient method is the association between the different hydrolysis methods mentioned. However, this alternative can increase the cost of the process. Enzymatic hydrolysis is the most studied method due to its environmental advantages and high specificity. However, hydrolysis time and process cost are factors that still limit industrial application. In addition, the enzymatic method has a limited association with other hydrolysis methods due to the sensitivity of the enzymes. Therefore, this article seeks to extensively review the variables that influence the main methods of hydrolysis: acid concentration, radiation intensity, potency, time, temperature, pH, and enzyme/substrate ratio, observing their influence on molecular weight, yield, and characteristic of the product.

Extraction, characterization and bioactivity of chitosan from farms shrimps of Basra province by chemical method

This paper include the extraction of chitin and transformation it to chitosan from the shrimps shells (waste) that grow up at sea farm in Al-Basra Province, the extraction done according to the literatures by two methods the difference between them was in the first step, but other steps were same methods, the results show sample A was higher than sample B in good yield and other physicochemical properties ( moisture, intrinsic viscosity, daacetylation degree, solubility, and fat binding capacity) which were measured to both samples, chitosan samples were characterization with FT-IR spectrum, in addition the biological activity for chitosan was tested against E.coli, P. asparagi, S. aureus, and B. cerus, the results show that sample A has inhibited these bacteria more than sample B.

Injectable hydrogel derived from chitosan with tunable mechanical properties via hybrid-crosslinking system

Thermo-sensitive injectable hydrogels that spontaneously react to physiological temperature have been widely studied to be used in biomedical fields. However, several challenges on their unstable structures with large-sized pores and low mechanical strength under physiological conditions must be addressed to enable their practical applications. We synthesized the hydroxybutyl methacrylated chitosan (HBC-MA) hydrogel that possesses both thermo-sensitive and photo-crosslinkable properties. The HBC-MA showed effective sol-gel transition under physiological temperature as well as a sensitive photo-crosslinkable property with visible light capable of skin penetration. The co-nonsolvency property and thermo-sensitivity of HBC-MA prevented unintended loss of the hydrogel graft after being subcutaneously injected in mice. Subsequently applied visible light on the skin beneath which the hydrogel was injected significantly improved the mechanical strength and stability of the graft. The injectable HBC-MA hydrogel developed in this study can be applicable to a wide range of biomedical fields such as drug delivery system and tissue engineering.

Chitin/Chitosan and Its Derivatives: Fundamental Problems and Practical Approaches

In this review, we present the data on the natural occurrence of chitin and its partially or fully deacetylated derivative chitosan, as well as their properties, methods of modification, and potential applications of derivatives with bactericidal, fungicidal, and antioxidant activities. The structure and physicochemical characteristics of the polymers, their functions, and features of chitin microbial synthesis and degradation, including the processes occurring in nature, are described. New data on the hydrolytic microorganisms capable of chitin degradation under extreme conditions are presented. Special attention is focused on the effect of physicochemical characteristics of chitosan, including molecular weight, degree of deacetylation, polydispersity index, and number of amino group derivatives (quaternized, succinyl, etc.) on the antimicrobial and antioxidant properties of modified polymers that can be of particular interest for biotechnology, medicine, and agriculture. Analysis of the available literature data confirms the importance of fundamental research to broaden our knowledge on the occurrence of chitin and chitosan in nature, their role in global biosphere cycles, and prospects of applied research aimed at using chitin, chitosan, and their derivatives in various aspects of human activity.

Microcystin-LR-induced changes of hepatopancreatic transcriptome, intestinal microbiota, and histopathology of freshwater crayfish (Procambarus clarkii)

As a hepatotoxin, microcystin-LR (MC-LR) poses a great threat to aquatic organisms. In this research, the hepatopancreatic transcriptome, intestinal microbiota, and histopathology of Procambarus clarkii (P. clarkii) in response to acute MC-LR exposure were studied. RNA-seq analysis of hepatopancreas identified 372 and 781 differentially expressed genes (DEGs) after treatment with 10 and 40 μg/L MC-LR, respectively. Among the DEGs, 23 genes were immune-related and 21 genes were redox-related. GO functional enrichment analysis revealed that MC-LR could impact nuclear-transcribed mRNA catabolic process, cobalamin- and heme-related processes, and sirohydrochlorin cobaltochelatase activity of P. clarkii. In addition, the only significantly enriched KEGG pathway induced by MC-LR was galactose metabolism pathway. Meanwhile, sequencing of the bacterial 16S rRNA gene demonstrated that MC-LR decreased bacterial richness and diversity, and altered the intestinal microbiota composition. At the phylum level, after 96 h, the abundance of Verrucomicrobia decreased after treatment with 10 and 40 μg/L MC-LR, while Firmicutes increased in the 40 μg/L MC-LR-treated group. At the genus level, the abundances of 15 genera were significantly altered after exposure to MC-LR. Our research demonstrated that MC-LR exposure caused histological alterations such as structural damage of hepatopancreas and intestines. This research provides an insight into the mechanisms associated with MC-LR toxicity in aquatic crustaceans.

Identification and characterization of virulent Aeromonas hydrophila Ah17 from infected Channa striata in river Cauvery and in vitro evaluation of shrimp chitosan

Aeromonas hydrophila, an inhabitant in the aquatic ecosystem is considered as an important foodborne bacterial zoonotic pathogen in aquaculture. The present study aimed to identify virulent A. hydrophila from naturally infected Channa striata in river Cauvery and in vitro evaluation of shrimp chitosan. Rimler Shotts (RS) and blood agar medium identified the presence of pathogenic Aeromonas sp. from the infected C. striata. A. hydrophila Ah17 was identified using 16S rRNA nucleotide sequence. Extracellular enzymes such as amylase, lipase, and protease were screened in A. hydrophila Ah17. Antibiotic susceptibility tests showed A. hydrophila Ah17 was highly resistant against β-lactam, glycopeptide, macrolides, phosphonic, fucidin, and oxazolidinone classes of antibiotics. Virulent genes such as hemolysin (aer and hly), heat-labile enterotoxin (act), cytotonic heat-stable enterotoxin (ast), elastase (ahyB), and lipase (lip) were identified. Growth and the viable cell population of virulent A. hydrophila Ah17 were significantly reduced in a dose-dependent manner against shrimp chitosan (CHS) from Penaeus indicus (P. indicus). Thus, the present study isolated virulent A. hydrophila Ah17 from the environmental source and characterized in vitro with shrimp chitosan.

Enzymatic Degradation of Nanosized Chitin Whiskers with Different Degrees of Deacetylation

In order to study the relationship between the degree of deacetylation of chitin whiskers (CHWs) and their enzymatic degradation properties, in this paper, CHWs were first deacetylated to different degrees by alkali treatment, and the CHWs with the degrees of deacetylation of 17.84, 67.76, and 82.54% was obtained, respectively. Moreover, the partially deacetylated CHWs still maintained good crystallinity and nanoneedle-like morphology. Next, the in vitro degradation behavior of CHWs with different degrees of deacetylation was further studied under the single or synergistic action of lysozyme and lipase (37 °C, pH = 7.4). The results showed that the morphology change of CHWs was more obvious as the degree of deacetylation increased. The mass loss, the crystallinity index at the (110) crystal plane, and the concentration of reducing sugar of the CHWs also increased with the degree of deacetylation. Moreover, the synergistic effect of the two enzymes was more conducive to the degradation process of CHWs than single lysozyme or lipase. The difference in the rate of enzymatic degradation provides an idea for the regulation of the degradation rate of the CHWs.

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.

Marine chitinolytic enzymes, a biotechnological treasure hidden in the ocean?

Chitinolytic enzymes are capable to catalyze the chitin hydrolysis. Due to their biomedical and biotechnological applications, nowadays chitinolytic enzymes have attracted worldwide attention. Chitinolytic enzymes have provided numerous useful materials in many different industries, such as food, pharmaceutical, cosmetic, or biomedical industry. Marine enzymes are commonly employed in industry because they display better operational properties than animal, plant, or bacterial homologs. In this mini-review, we want to describe marine chitinolytic enzymes as versatile enzymes in different biotechnological fields. In this regard, interesting comments about their biological role, reaction mechanism, production, functional characterization, immobilization, and biotechnological application are shown in this work.

Chitosan oligosaccharide-N-chlorokojic acid mannich base polymer as a potential antibacterial material

Here, a nontoxic antibacterial material based on Chitosan Oligosaccharide-N-Chlorokojic acid Mannich base (COS-N-MB) that was synthesized by using the selective partial alkylation reaction displaying excellent activity against bacterial infection. The proposed mechanism of the action of COS-N-MB is that this antibacterial material with positive charge and synergistic antibacterial effects can promote it's adsorption to bacterial cell wall through electrostatic interaction and chelating metal cations. It changed the permeability of the membrane, caused cellular leakage, and destroyed the membrane integrity, leading to complete membrane disruption and eventually death of the bacteria. Besides, COS-N-MB can interact with membrane proteins, causing deformation in the structure and functionality. The good biocompatibility, noncytotoxic, and low hemolysis made this novel material a promising and effective compound for antibacterial applications.

Antimicrobial activity of Fe-loaded chitosan nanoparticles

To increase the antimicrobial activities of chitosan, chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ were prepared by surfactant-assisted chitosan chelating Fe²⁺, Fe³⁺ and ionic gelation chitosan. Their chelating rates were determined by spectrophotometry. The particle sizes and zeta potentials of chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ were measured by size and zeta potential analysis. The nanoparticles antimicrobial activities were evaluated by different concentration against Escherichia coli, Staphylococcus aureus, Candida albicans in vitro. Results showed that the mean diameter of chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ were 206.4 and 195.2 nm, respectively. Their zeta potentials were +28.82 and +28.26 mV, respectively. The chelating rate of chitosan nanoparticles loaded with Fe²⁺ was greatly higher than with Fe³⁺. Their antimicrobial activity was showed greatly higher at lower concentrations compared to chitosan, and the antibacterial effect of chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ was preliminary observed.

Novel Amino-Pyridine Functionalized Chitosan Quaternary Ammonium Derivatives: Design, Synthesis, and Antioxidant Activity

Chemical modification of chitosan is increasingly studied for its potential of providing new applications of chitosan. Here, a group of novel chitosan quaternary ammonium derivatives containing pyridine or amino-pyridine were designed and successfully synthesized through chemical modification of chitosan. Pyridine and amino-pyridine were used as functional groups to improve the antifungal activity of chitosan derivatives. The chitosan derivatives' antioxidant activity against hydroxyl-radical and 1,1-Diphenyl-2-picrylhydrazyl (DPPH)-radical was tested in vitro. The results showed that chitosan derivatives had better water solubility and stronger antioxidant activity compared with chitosan in all assays. Especially, compounds 3C and 3E (with 3-amino pyridine and 2,3-diamino pyridine as substitute respectively) exhibited stronger hydroxyl-radical and DPPH-radical scavenging ability than other synthesized compounds. These data demonstrated that the synergistic effect of the amino group and pyridine would improve the antioxidant activity of chitosan derivatives, and the position of the amino group on pyridine could influence the antioxidant property of chitosan derivatives.

Antimicrobial and Antioxidant Activity of Chitosan/Hydroxypropyl Methylcellulose Film-Forming Hydrosols Hydrolyzed by Cellulase

The aim of this study was to evaluate the impact of cellulase (C) on the biological activity of chitosan/hydroxypropyl methylcellulose (CH/HPMC) film-forming hydrosols. The hydrolytic activity of cellulase in two concentrations (0.05% and 0.1%) was verified by determination of the progress of polysaccharide hydrolysis, based on viscosity measurement and reducing sugar-ends assay. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging effect, the ferric reducing antioxidant power (FRAP), and microbial reduction of Pseudomonas fluorescens, Yersinia enterocolitica, Bacillus cereus, and Staphylococcus aureus were studied. During the first 3 h of reaction, relative reducing sugar concentration increased progressively, and viscosity decreased rapidly. With increasing amount of enzyme from 0.05% to 0.1%, the reducing sugar concentration increased, and the viscosity decreased significantly. The scavenging effect of film-forming solutions was improved from 7.6% at time 0 and without enzyme to 52.1% for 0.1% cellulase after 20 h of reaction. A significant effect of cellulase addition and reaction time on antioxidant power of the tested film-forming solutions was also reported. Film-forming hydrosols with cellulase exhibited a bacteriostatic effect on all tested bacteria, causing a total reduction.

Enzymes from Seafood Processing Waste and Their Applications in Seafood Processing

Commercial fishery processing results in discards up to 50% of the raw material, consisting of scales, shells, frames, backbones, viscera, head, liver, skin, belly flaps, dark muscle, roe, etc. Besides, fishing operations targeted at popular fish and shellfish species also result in landing of sizeable quantity of by-catch, which are not of commercial value because of their poor consumer appeal. Sensitivity to rapid putrefaction of fishery waste has serious adverse impact on the environment, which needs remedial measures. Secondary processing of the wastes has potential to generate a number of valuable by-products such as proteins, enzymes, carotenoids, fat, and minerals, besides addressing environmental hazards. Fishery wastes constitute good sources of enzymes such as proteases, lipases, chitinase, alkaline phosphatase, transglutaminase, hyaluronidase, acetyl glycosaminidase, among others. These enzymes can have diverse applications in the seafood industry, which encompass isolation and modification of proteins and marine oils, production of bioactive peptides, acceleration of traditional fermentation, peeling and deveining of shellfish, scaling of finfish, removal of membranes from fish roe, extraction of flavors, shelf life extension, texture modification, removal of off-odors, and for quality control either directly or as components of biosensors. Enzymes from fish and shellfish from cold habitats are particularly useful since they can function comparatively at lower temperatures thereby saving energy and protecting the food products. Potentials of these applications are briefly discussed.

Antimicrobial Activities of Nisin, Tea Polyphenols, and Chitosan and their Combinations in Chilled Mutton

Antimicrobial activities of nisin, tea polyphenols (TPs), and chitosan, and their combinations were evaluated against both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB) by the agar dilution method. Results showed that the MIC of nisin was 2.44 to 1250 mg/L for GPB and reached 5000 mg/L for GNB. The MICs of TPs and chitosan were 313 to 625 mg/L and 469 mg/L for GNB, and 156 to 5000 mg/L and 234 to 938 mg/L for GPB, respectively. These results indicated that TPs and chitosan exhibited inhibitory effects against both GPB and GNB, whereas nisin inhibited the growth of GPB only. Based on the orthogonal test of their MICs, and evaluation of preservative effect and sensory attributes in chilled mutton, the optimum combination was chosen as 0.625, 0.313, and 3.752 g/L for nisin, TPs, and chitosan, respectively. By using the optimum treatment, the shelf life of chilled mutton was extended from 6 to 18 d at 4 °C in the preservative film packages. These results indicate that the combination of nisin, TPs, and chitosan could be used as preservatives to efficiently inhibit the growth of spoilage microorganisms and pathogens in meat, thus improving the safety and shelf life of chilled mutton.