Bioproduction of chitooligosaccharides: present and perspectives

Chitosanase-immobilized magnetite-agar gel particles as a highly stable and reusable biocatalyst for enhanced production of physiologically active chitosan oligosaccharides

A novel immobilized chitosanase was developed and utilized to produce chitosan oligosaccharides (COSs) via chitosan hydrolysis. Magnetite-agar gel particles (average particle diameter: 338 μm) were prepared by emulsifying an aqueous agar solution dispersing 200-nm magnetite particles with isooctane containing an emulsifier at 80 °C, followed by cooling the emulsified mixture. The chitosanase from Bacillus pumilus was immobilized on the magnetite-agar gel particles chemically activated by introducing glyoxyl groups with high immobilization yields (>80%), and the observed specific activity of the immobilized chitosanase was 16% of that of the free enzyme. This immobilized chitosanase could be rapidly recovered from aqueous solutions by applying magnetic force. The thermal stability of the immobilized chitosanase improved remarkably compared with that of free chitosanase: the deactivation rate constants at 35 °C of the free and immobilized enzymes were 8.1 × 10-5 and 3.9 × 10-8 s-1, respectively. This immobilized chitosanase could be reused for chitosan hydrolysis at 75 °C and pH 5.6, and 80% of its initial activity was maintained even after 10 cycles of use. COSs with a degree of polymerization (DP) of 2-7 were obtained using this immobilized chitosanase, and the product content of physiologically active COSs (DP ≥ 5) reached approximately 50%.

Chitosan and Chitooligosaccharides: Antifungal Potential and Structural Insights

Chitosan is a cationic polysaccharide derived from chitin deacetylation. This polysaccharide and its oligosaccharides have many biological activities and can be used in several fields due to their favorable characteristics, such as biodegradability, biocompatibility, and nontoxicity. This review aims to explore the antifungal potential of chitosan and chitooligosaccharides along with the conditions used for the activity and mechanisms of action they use to kill fungal cells. The sources, chemical properties, and applications of chitosan and chitooligosaccharides are discussed in this review. It also addresses the threat fungi pose to human health and crop production and how these saccharides have proven to be effective against these microorganisms. The cellular processes triggered by chitosan and chitooligosaccharides in fungal cells, and prospects for their use as potential antifungal agents are also examined.

Physiological and Proteome Analysis of the Effects of Chitosan Oligosaccharides on Salt Tolerance of Rice Seedlings

Rice (Oryza sativa L.) is an important social-economic crop, and rice seedlings are easily affected by salt stress. Chitosan oligosaccharide (COS) plays a positive role in promoting plant growth and development. To gain a better understanding of the salt tolerance mechanism of rice under the action of COS, Nipponbare rice seedlings were selected as the experimental materials, and the physiological and biochemical indexes of rice seedlings in three stages (normal growth, salt stress and recovery) were measured. Unlabelled quantitative proteomics technology was used to study differential protein and signaling pathways of rice seedlings under salt stress, and the mechanism of COS to improve rice tolerance to salt stress was elucidated. Results showed that after treatment with COS, the chlorophyll content of rice seedlings was 1.26 times higher than that of the blank group (CK). The root activity during the recovery stage was 1.46 times that of the CK group. The soluble sugar in root, stem and leaf increased by 53.42%, 77.10% and 9.37%, respectively. The total amino acid content increased by 77% during the stem recovery stage. Furthermore, the malondialdehyde content in root, stem and leaf increased by 21.28%, 26.67% and 32.69%, respectively. The activity of oxide dismutase (SOD), peroxidase (POD) and oxygenase (CAT) were increased. There were more differentially expressed proteins in the three parts of the experimental group than in the CK group. Gene Ontology (GO) annotation of these differentially expressed proteins revealed that the experimental group was enriched for more entries. Then, through the Kyoto Encyclopedia of Genes and Genomes (KEGG), the top ten pathways enriched with differentially expressed proteins in the two groups (COS and CK groups) were utilized, and a detailed interpretation of the glycolysis and photosynthesis pathways was provided. Five key proteins, including phosphofructokinase, fructose bisphosphate aldolases, glycer-aldehyde-3-phosphate dehydrogenase, enolase and pyruvate kinase, were identified in the glycolysis pathway. In the photosynthesis pathway, oxygen evolution enhancement proteins, iron redox proteins and ferredoxin-NADPH reductase were the key proteins. The addition of COS led to an increase in the abundance of proteins, a response of rice seedlings to salt stress. COS helped rice seedlings resist salt stress. Furthermore, using COS as biopesticides and biofertilizers can effectively increase the utilization of saline-affected farmland, thereby contributing to the alleviating of the global food crisis.

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.

Analysis of molecular structure and topological properties of chitosan isolated from crab shell and mushroom

This investigation aimed to scrutinize the chemical and structural analogies between chitosan extracted from crab exoskeleton (High Molecular Weight Chitosan, HMWC) and chitosan obtained from mushrooms (Mushroom-derived Chitosan, MRC), and to assess their biological functionalities. The resulting hydrolysates from the hydrolysis of HMWC by chitosanase were categorized as chitosan oligosaccharides (csCOS), while those from MRC were denoted as mrCOS. The molecular weights (MW) of csCOS and mrCOS were determined using Matrix-Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry. Furthermore, structural resemblances of csCOS and mrCOS were assessed utilizing X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Intriguingly, no apparent structural disparity between csCOS and mrCOS was noted in terms of the glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) composition ratios. Consequently, the enzymatic activities of chitosanase for HMWC and MRC exhibited remarkable similarity. A topological examination was performed between the enzyme and the substrate to deduce the alteration in MW of COSs following enzymatic hydrolysis. Moreover, the evaluation of antioxidant activity for each COS revealed insignificance in the structural disparity between HMWC and MRC. In summary, grounded on the chemical structural similarity of HMWC and MRC, we propose the potential substitution of HMWC with MRC, incorporating diverse biological functionalities.

A novel N-acetylglucosamine-6-phosphate deacetylase that is essential for chitin utilization in the chitinolytic bacterium, Chitiniphilus shinanonensis

AIMS

We aimed to investigate the function of an unidentified gene annotated as a PIG-L domain deacetylase (cspld) in Chitiniphilus shinanonensis SAY3. cspld was identified using transposon mutagenesis, followed by negatively selecting a mutant incapable of growing on chitin, a polysaccharide consisting of N-acetyl-d-glucosamine (GlcNAc). We focused on the physiological role of CsPLD protein in chitin utilization.

METHODS AND RESULTS

Recombinant CsPLD expressed in Escherichia coli exhibited GlcNAc-6-phosphate deacetylase (GPD) activity, which is involved in the metabolism of amino sugars. However, SAY3 possesses two genes (csnagA1 and csnagA2) in its genome that code for proteins whose primary sequences are homologous to those of typical GPDs. Recombinant CsNagA1 and CsNagA2 also exhibited GPD activity with 23 and 1.6% of catalytic efficiency (kcat/Km), respectively, compared to CsPLD. The gene-disrupted mutant, Δcspld was unable to grow on chitin or GlcNAc, whereas the three mutants, ΔcsnagA1, ΔcsnagA2, and ΔcsnagA1ΔcsnagA2 grew similarly to SAY3. The determination of GPD activity in the crude extracts of each mutant revealed that CsPLD is a major enzyme that accounts for almost all cellular activities.

CONCLUSIONS

Deacetylation of GlcNAc-6P catalyzed by CsPLD (but not by typical GPDs) is essential for the assimilation of chitin and its constituent monosaccharide, GlcNAc, as a carbon and energy source in C. shinanonensis.

A novel endo-type chitinase possessing chitobiase activity derived from the chitinolytic bacterium, Chitiniphilus shinanonensis SAY3T

One of the chitinases (ChiG) derived from the chitinolytic bacterium Chitiniphilus shinanonensis SAY3T exhibited chitobiase activity cleaving dimers of N-acetyl-D-glucosamine (GlcNAc) into monomers, which is not detected in typical endo-type chitinases. Analysis of the reaction products for GlcNAc hexamers revealed that all the five internal glycosidic bonds were cleaved at the initial stage. The overall reaction catalyzed by chitobiases toward GlcNAc dimers was similar to that catalyzed by N-acetyl-D-glucosaminidases (NAGs). SAY3 possesses two NAGs (ChiI and ChiT) that are thought to be important in chitin catabolism. Unexpectedly, a triple gene-disrupted mutant (ΔchiIΔchiTΔchiG) was still able to grow on synthetic medium containing GlcNAc dimers or powdered chitin, similar to the wild-type SAY3, although it exhibited only 3% of total cellular NAG activity compared to the wild-type. This indicates the presence of unidentified enzyme(s) capable of supporting normal bacterial growth on the chitin medium by NAG activity compensation.

Multi-enzyme Machinery for Chitin Degradation in the Chitinolytic Bacterium Chitiniphilus shinanonensis SAY3T

The chitinolytic bacterium, Chitiniphilus shinanonensis SAY3T was examined to characterize its chitin-degrading enzymes in view of its potential to convert biomass chitin into useful saccharides. A survey of the whole-genome sequence revealed 49 putative genes encoding polypeptides that are thought to be related to chitin degradation. Based on an analysis of the relative quantity of each transcript and an assay for chitin-degrading activity of recombinant proteins, a chitin degradation system driven by 19 chitinolytic enzymes was proposed. These include sixteen endo-type chitinases, two N-acetylglucosaminidases, and one lipopolysaccharide monooxygenase that catalyzes the oxidative cleavage of glycosidic bonds. Among the 16 chitinases, ChiL was characterized by its remarkable transglycosylation activity. Of the two N-acetylglucosaminidases (ChiI and ChiT), ChiI was the major enzyme, corresponding to > 98% of the total cellular activity. Surprisingly, a chiI-disrupted mutant was still able to grow on medium with powdered chitin or GlcNAc dimer. However, its growth rate was slightly lower compared to that of the wild-type SAY3. This multi-enzyme machinery composed of various types of chitinolytic enzymes may support SAY3 to efficiently utilize native chitin as a carbon and energy source and may play a role in developing an enzymatic process to decompose and utilize abundant chitin at the industrial scale.

Green-Chemical Strategies for Production of Tailor-Made Chitooligosaccharides with Enhanced Biological Activities

Chitooligosaccharides (COSs) are b-1,4-linked homo-oligosaccharides of N-acetylglucosamine (GlcNAc) or glucosamine (GlcN), and also include hetero-oligosaccharides composed of GlcNAc and GlcN. These sugars are of practical importance because of their various biological activities, such as antimicrobial, anti-inflammatory, antioxidant and antitumor activities, as well as triggering the innate immunity in plants. The reported data on bioactivities of COSs used to contain some uncertainties or contradictions, because the experiments were conducted with poorly characterized COS mixtures. Recently, COSs have been satisfactorily characterized with respect to their structures, especially the degree of polymerization (DP) and degree of N-acetylation (DA); thus, the structure-bioactivity relationship of COSs has become more unambiguous. To date, various green-chemical strategies involving enzymatic synthesis of COSs with designed sequences and desired biological activities have been developed. The enzymatic strategies could involve transglycosylation or glycosynthase reactions using reducing end-activated sugars as the donor substrates and chitinase/chitosanase and their mutants as the biocatalysts. Site-specific chitin deacetylases were also proposed to be applicable for this purpose. Furthermore, to improve the yields of the COS products, metabolic engineering techniques could be applied. The above-mentioned approaches will provide the opportunity to produce tailor-made COSs, leading to the enhanced utilization of chitin biomass.

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

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

Enhanced production of N-acetyl-glucosaminidase by marine Aeromonas caviae CHZ306 in bioreactor

N-Acetyl-glucosaminidases (GlcNAcases) are exoenzymes found in a wide range of living organisms, which have gained great attention in the treatment of disorders related to diabetes, Alzheimer's, Tay-Sachs', and Sandhoff's diseases; the control of phytopathogens; and the synthesis of bioactive GlcNAc-containing products. Aiming at future industrial applications, in this study, GlcNAcase production by marine Aeromonas caviae CHZ306 was enhanced first in shake flasks in terms of medium composition and then in bench-scale stirred-tank bioreactor in terms of physicochemical conditions. Stoichiometric balance between the bioavailability of carbon and nitrogen in the formulated culture medium, as well as the use of additional carbon and nitrogen sources, played a central role in improving the bioprocess, considerably increasing the enzyme productivity. The optimal cultivation medium was composed of colloidal α-chitin, corn steep liquor, peptone A, and mineral salts, in a 5.2 C:N ratio. Optimization of pH, temperature, colloidal α-chitin concentration, and kLa conditions further increased GlcNAcase productivity. Under optimized conditions in bioreactor (i.e., 34 °C, pH 8 and kLa 55.2 h-1), GlcNAcase activity achieved 173.4 U.L-1 after 12 h of cultivation, and productivity no less than 14.45 U.L-1.h-1 corresponding to a 370-fold enhancement compared to basal conditions.

Bioconversion of chitin into chitin oligosaccharides using a novel chitinase with high chitin-binding capacity

Chitin is the second largest renewable biomass resource in nature, it can be enzymatically degraded into high-value chitin oligosaccharides (CHOSs) by chitinases. In this study, a chitinase (ChiC8-1) was purified and biochemically characterized, its structure was analyzed by molecular modeling. ChiC8-1 had a molecular mass of approximately 96 kDa, exhibited its optimal activity at pH 6.0 and 50 °C. The K_m and V_max values of ChiC8-1 towards colloidal chitin were 10.17 mg mL^-1 and 13.32 U/mg, respectively. Notably, ChiC8-1 showed high chitin-binding capacity, which may be related to the two chitin binding domains in the N-terminal. Based on the unique properties of ChiC8-1, a modified affinity chromatography method, which combines protein purification with chitin hydrolysis process, was developed to purify ChiC8-1 while hydrolyzing chitin. In this way, 9.36 ± 0.18 g CHOSs powder was directly obtained by hydrolyzing 10 g colloidal chitin with crude enzyme solution. The CHOSs were composed of 14.77-2.83 % GlcNAc and 85.23-97.17 % (GlcNAc)₂ at different enzyme-substrate ratio. This process simplifies the tedious purification and separation steps, and may enable its potential application in the field of green production of chitin oligosaccharides.

Endochitinase and Chitobiosidase Production by Marine Aeromonas caviae CHZ306: Establishment of Nitrogen Supplementation

Aeromonas caviae CHZ306, a marine-derived bacterium isolated from zooplankton, can use chitin (a polymer of a β-(1,4)-linked N-acetyl-D-glucosamine) as a carbon source. The chitin is hydrolyzed by chitinolytic enzymes, namely endochitinases and exochitinases (chitobiosidase and N-acetyl-glucosaminidase). Indeed, the chitinolytic pathway is initiated by the coexpression of the enzymes endochitinase (EnCh) and chitobiosidase (ChB); however, few studies, including biotechnological production of these enzymes, have been reported, although chitosaccharide are helpful in several industries, such as cosmetics. This study demonstrates the potential to maximize the simultaneous EnCh and ChB production by nitrogen supplementation on culture media. Twelve different nitrogen supplementation sources (inorganic and organic) previously analyzed in elemental composition (carbon and nitrogen) were tested and evaluated in the Erlenmeyer flask culture of A. caviae CHZ306 for EnCh and ChB expression. None of the nutrients inhibited bacterial growth, and the maximum activity in both EnCh and ChB was observed at 12 h, using corn-steep solids and peptone A. Corn-steep solids and peptone A were then combined at three ratios (1:1, 1:2, and 2:1) to maximize the production. The high activities for EnCh (30.1 U.L−1) and ChB (21.3 U.L−1) were obtained with 2:1 corn-steep solids and peptone A, corresponding to more than 5- and 3-fold enhancement, respectively, compared to the control condition.

A review on extraction of polysaccharides from crustacean wastes and their environmental applications

Disposal of biodegradable waste of seashells leads to an environmental imbalance. A tremendous amount of wastes produced from flourishing shell fish industries while preparing crustaceans for human consumption can be directed towards proper utilization. The review of the present study focuses on these polysaccharides from crustaceans and a few important industrial applications. This review aimed to emphasize the current research on structural analyses and extraction of polysaccharides. The article summarises the properties of chitin, chitosan, and chitooligosaccharides and their derivatives that make them non-toxic, biodegradable, and biocompatible. Different extraction methods of chitin, chitosan, and chitooligosaccharides have been discussed in detail. Additionally, this information outlines possible uses for derivatives of chitin, chitosan, and chitooligosaccharides in the environmental, pharmaceutical, agricultural, and food industries. Additionally, it is essential to the textile, cosmetic, and enzyme-immobilization industries. This review focuses on new, insightful suggestions for raising the value of crustacean shell waste by repurposing a highly valuable material.

Characterization of different chitosanases of Bacillus strains and their application in chitooligosaccharides production

Chitosanases are potential candidates for chitooligosaccharides (COS) production-based industries, therefore, the discovery of chitosanases having commercial potential will remain a priority worldwide. This study aims to characterize different chitosanases of Bacillus strains for COS production. Six different indigenous Bacillus strains (B. cereus EGE-B-6.1m, B. cereus EGE-B-2.5m, B. cereus EGE-B-5.5m, B. cereus EGE-B-10.4i, B. thuringiensis EGE-B-3.5m, and B. mojavensis EGE-B-5.2i) were used to purify and characterize chitosanases. All purified chitosanases have a similar molecular weight (37 kDa) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, other characteristics such as optimum temperature and pH, kinetic parameters (K_m and V_max ), temperature, and pH stabilities were dissimilar among the strains of different Bacillus species and within the same species. Furthermore, chitosanases of all strains were able to successfully hydrolyze chitosan to COS and oligomers of the degree of polymerization 2-6 were detected with chitobiose and chitotriose as major hydrolysis products. The relative yields of COS were in a range of 19%-31% and chitosanase of B. thuringiensis EGE-B-3.5m turned out to be the best enzyme in terms of its characteristics and COS production potential with maximum relative yield (31%). Results revealed that Bacillus chitosanases could be used directly for efficient bioconversion of chitosan into COS and will be valuable for large-scale production of biologically active COS.

Effects of fungal based bioactive compounds on human health: Review paper

Since the first years of history, microbial fermentation products such as bread, wine, yogurt and vinegar have always been noteworthy regarding their nutritional and health effects. Similarly, mushrooms have been a valuable food product in point of both nutrition and medicine due to their rich chemical components. Alternatively, filamentous fungi, which can be easier to produce, play an active role in the synthesis of some bioactive compounds, which are also important for health, as well as being rich in protein content. Therefore, this review presents some important bioactive compounds (bioactive peptides, chitin/chitosan, β-glucan, gamma-aminobutyric acid, L-carnitine, ergosterol and fructooligosaccharides) synthesized by fungal strains and their health benefits. In addition, potential probiotic- and prebiotic fungi were researched to determine their effects on gut microbiota. The current uses of fungal based bioactive compounds for cancer treatment were also discussed. The use of fungal strains in the food industry, especially to develop innovative food production, has been seen as promising microorganisms in obtaining healthy and nutritious food.

Nematicidal Properties of Chitosan Nanoformulation

Chitosan is the second most abundant bio-polymer available in the world, second only to cellulose. It is found in crustaceous shells, e.g., those of crabs, shrimps, prawns, and fungi, as well as insect exoskeletons. The use of nanoformulations for the management of pests and diseases is receiving increased interest with the advancement of nanotechnology. Here, chitosan nanospheres were obtained from chitosan using the ionic gelation technique. The nanoformulations obtained were characterized using a particle size analyzer, Fourier transform infrared spectroscopy, and a transmission electron microscope. The efficacy of chitosan nanospheres in suppressing the root-knot nematode Meloidogyne incognita was studied. The particle size of nanospheres formulated for this study was 380.2 nm, with a polydispersity index (PI) of 0.4 and Zeta potential of 45.7 or 50.9 mV at pH 5.2. The chitosan nanospheres were spherical and the particles did not agglomerate. FTIR spectra of the chitosan nanospheres peaked at 3334 cm-1, thereby indicating the stretching of the OH and NH group. In In-vitro studies, chitosan nanospheres showed significant nematicidal activity against M. incognita. Under pot culture conditions, chitosan nanospheres (1%- active compound chitosan) at 2ml/plant decreased the nematode population in roots or soil. Compared to the control, the number of galls was reduced by 83.68%, the number of egg masses by 83.85%, the number of adult females by 66.56%, and the number of second-stage juveniles by 73.20%. In a field experiment, application of chitosan nanospheres (1%) was followed by a 18.75% increase in fruit yield compared to the non-treated control.

Giant Viruses as a Source of Novel Enzymes for Biotechnological Application

The global demand for industrial enzymes has been increasing in recent years, and the search for new sources of these biological products is intense, especially in microorganisms. Most known viruses have limited genetic machinery and, thus, have been overlooked by the enzyme industry for years. However, a peculiar group of viruses breaks this paradigm. Giant viruses of the phylum Nucleocytoviricota infect protists (i.e., algae and amoebae) and have complex genomes, reaching up to 2.7 Mb in length and encoding hundreds of genes. Different giant viruses have robust metabolic machinery, especially those in the Phycodnaviridae and Mimiviridae families. In this review, we present some peculiarities of giant viruses that infect protists and discuss why they should be seen as an outstanding source of new enzymes. We revisited the genomes of representatives of different groups of giant viruses and put together information about their enzymatic machinery, highlighting several genes to be explored in biotechnology involved in carbohydrate metabolism, DNA replication, and RNA processing, among others. Finally, we present additional evidence based on structural biology using chitinase as a model to reinforce the role of giant viruses as a source of novel enzymes for biotechnological application.

Gene cloning and molecular characterization of a thermostable chitosanase from Bacillus cereus TY24

Background

An important conceptual advance in health and the environment has been recognized that enzymes play a key role in the green processing industries. Of particular interest, chitosanase is beneficial for recycling the chitosan resource and producing chitosan oligosaccharides. Also, chitosan gene expression and molecular characterization will promote understanding of the biological function of bacterial chitosanase as well as explore chitosanase for utilizing chitosan resources.

Results

A chitosanase-producing bacterium TY24 was isolated and identified as Bacillus cereus. Moreover, the chitosanase gene was cloned and expressed in Escherichia coli. Sequence analysis reveals that the recombinant chitosanase (CHOE) belongs to the glycoside hydrolases 8 family. The purified CHOE has a molecular weight of about 48 kDa and the specific activity of 1150 U/mg. The optimal pH and temperature of CHOE were 5.5 and 65 °C, respectively. The enzyme was observed stable at the pH range of 4.5–7.5 and the temperature range of 30–65 °C. Especially, the half-life of CHOE at 65 °C was 161 min. Additionally, the activity of CHOE was remarkably enhanced in the presence of Mn²⁺, Cu²⁺, Mg²⁺ and K⁺, beside Ca²⁺ at 5 mM. Especially, the activity of CHOE was enhanced to more than 120% in the presence of 1% of various surfactants. CHOE exhibited the highest substrate specificity toward colloid chitosan.

Conclusion

A bacterial chitosanase was cloned from B. cereus and successfully expressed in E. coli (BL21) DE3. The recombinant enzyme displayed good stability under acid pH and high-temperature conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-022-00762-6.

Insights into promiscuous chitosanases: the known and the unknown

Chitosanase, a glycoside hydrolase (GH), catalyzes the cleavage of β-1,4-glycosidic bonds in polysaccharides and is widely distributed in nature. Many organisms produce chitosanases, and numerous chitosanases in the GH families have been intensely studied. The reported chitosanases mainly cleaved the inter-glucosamine glycosidic bonds, while substrate specificity is not strictly unique due to the existence of bifunctional or multifunctional activity profiles. The promiscuity of chitosanases is essential for the different pathways of biomass polysaccharide conversion and understanding of the chitosanase evolutionary process. However, the reviews for this aspect are completely unknown. This review provides an overview of the promiscuous activities, also considering the substrate and product specificity of chitosanases observed to date. These contribute to important implications for the future discovery and research of promiscuous chitosanases and applications related to biomass conversion. KEY POINTS: • The promiscuity of chitosanases is reviewed for the first time. • The current review provides insights into the substrate specificity of chitosanases. • The mode-product relationship and prospect of promiscuous chitosanases are highlighted.

Potential Medical Applications of Chitooligosaccharides

Chitooligosaccharides, also known as chitosan oligomers or chitooligomers, are made up of chitosan with a degree of polymerization (DP) that is less than 20 and an average molecular weight (MW) that is lower than 3.9 kDa. COS can be produced through enzymatic conversions using chitinases, physical and chemical applications, or a combination of these strategies. COS is of significant interest for pharmacological and medical applications due to its increased water solubility and non-toxicity, with a wide range of bioactivities, including antibacterial, anti-inflammatory, anti-obesity, neuroprotective, anticancer, and antioxidant effects. This review aims to outline the recent advances and potential applications of COS in various diseases and conditions based on the available literature, mainly from preclinical research. The prospects of further in vivo studies and translational research on COS in the medical field are highlighted.

The Preparation and Characterization of Chitooligosaccharide–Polylactide Polymers, and In Vitro Release of Microspheres Loaded with Vancomycin

Drug-loaded microspheres are an ideal bone tissue delivery material. In this study, a biodegradable Schiff base chitosan–polylactide was used as the encapsulation material to prepare drug-loaded microspheres as biocompatible carriers for controlled vancomycin release. In this regard, Schiff base chitosan was prepared by the Schiff base method, and then different proportions of the Schiff base chitosan–polylactide polymer were prepared by ring-opening polymerization. Drug-loaded microspheres were prepared by the W/O emulsion method, and the polymers and polymer microspheres were characterized and studied by NMR, IR, and antibacterial methods. The drug loading and release rates of microspheres were determined to investigate the drug loading, encapsulation efficiency, and release rate of drug microspheres at different ratios. In this study, different proportions of Schiff base chitosan–polylactic acid materials are successfully prepared, and vancomycin-loaded microspheres are successfully prepared using them as carriers. This study proves that the materials have antibacterial activities against Staphylococcus aureus and Escherichia coli. The particle size of drug-loaded microspheres was below 10 μm, and the particle size decreased with decreasing molecular weight. The obtained results show that 1:100 microspheres have the highest drug-loading and encapsulation efficiencies, the drug-loaded microspheres have no burst release within 24 h, and the release quantity reaches more than 20%. After 30 days of release, the release amounts of 1:10, 1:20, 1:40, 1:60, and 1:100 drug-loaded microspheres were 64.80 ± 0.29%, 54.43 ± 0.54%, 44.60 ± 0.43%, 42.53 ± 0.40% and 69.73 ± 0.45%, respectively, and the release amount of 1:100 was the highest.

Chitosan Oligosaccharide Attenuates Lipopolysaccharide-Induced Intestinal Barrier Dysfunction through Suppressing the Inflammatory Response and Oxidative Stress in Mice

This study was conducted to investigate the protective effect of chitosan oligosaccharide (COS) against lipopolysaccharide (LPS)-induced intestinal injury. The results demonstrated that COS improved the mucosal morphology of the jejunum and colon in LPS-challenged mice. COS alleviated the LPS-induced down-regulation of tight junction protein expressions and reduction of goblet cells number and mucin expression. The mRNA expressions of anti-microbial peptides secreted by the intestinal cells were also up-regulated by COS. Additionally, COS decreased pro-inflammatory cytokine production and neutrophil recruitment in the jejunum and colon of LPS-treated mice. COS ameliorated intestinal oxidative stress through up-regulating the mRNA expressions of nuclear factor E2-related factor 2 and downstream antioxidant enzymes genes. Correlation analysis indicated that the beneficial effects of COS on intestinal barrier function were associated with its anti-inflammatory activities and antioxidant capacity. Our study provides evidence for the application of COS to the prevention of intestinal barrier dysfunction caused by the stress of a LPS challenge.

Recent advances of chitosan-based polymers in biomedical applications and environmental protection

Interest in polymer-based biomaterials such as chitosan and its modifications and also the methods of their application in various fields of science is uninterruptedly growing. Owing to unique physicochemical, biological, ecological, physiological properties, such as biocompatibility, biodegradability, stability in the natural environment, non-toxicity, high biological activity, economic affordability, chelating of metal ions, high sorption properties, chitosan is used in various biomedical and industrial processes. The reactivity of the amino and hydroxyl groups in the structure makes it more interesting for diverse applications in drug delivery, tissue engineering, wound healing, regenerative medicine, blood anticoagulation and bone, tendon or blood vessel engineering, dentistry, biotechnology, biosensing, cosmetics, water treatment, agriculture. Taking into account the current situation in the world with COVID-19 and other viruses, chitosan is also active in the form of a vaccine system, it can deliver antibodies to the nasal mucosa and load gene drugs that prevent or disrupt the replication of viral DNA/RNA, and deliver them to infected cells. The presented article is an overview of the nowaday state of the application of chitosan, based on literature of recent years, showing importance of fundamental and applied studies aimed to expand application of chitosan-based polymers in many fields of science.

Characteristics of Marine Biomaterials and Their Applications in Biomedicine

Oceans have vast potential to develop high-value bioactive substances and biomaterials. In the past decades, many biomaterials have come from marine organisms, but due to the wide variety of organisms living in the oceans, the great diversity of marine-derived materials remains explored. The marine biomaterials that have been found and studied have excellent biological activity, unique chemical structure, good biocompatibility, low toxicity, and suitable degradation, and can be used as attractive tissue material engineering and regenerative medicine applications. In this review, we give an overview of the extraction and processing methods and chemical and biological characteristics of common marine polysaccharides and proteins. This review also briefly explains their important applications in anticancer, antiviral, drug delivery, tissue engineering, and other fields.

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.

Chitooligosaccharides production from shrimp chaff in chitosanase cell surface display system

Chitin refers to a natural biopolymer, which is economically significant to next-generation biorefineries. In this study, a novel high-yield method with cell surface-display chitosanase (CHI-1) was built to produce chitooligosaccharides (COS) from shrimp chaff through the co-fermentation in the presence of Bacillus subtilis and Acetobacter sp. Under the optimized co-fermentation conditions (5 g/L yeast extracts, 10 g/L KH₂PO₄, 6% ethanol, 50 g/L glucose), the final deproteinization (DP) and demineralization (DM) efficiency and the chitin yield were achieved as 94, 92 and 18%, respectively. The engineered E. coli BL21-pET23b(+)-NICHI maintained 81% of the initial enzyme activity after 40 days at room temperature. The crude CHI-1 was inactivated after one-day interacting with prepared chitosan. Moreover, E. coli BL21-pET23b(+)-NICHI still maintained excellent hydrolysis ability in 7 days, and the COS yield reached 41%. Accordingly, the proposed method exhibited excellent stability and a high hydrolysis efficiency to produce COS with whole engineered cells.

Combinatorial pathway engineering of Bacillus subtilis for production of structurally defined and homogeneous chitooligosaccharides

Chitooligosaccharides (COSs) have a widespread range of biological functions and an incredible potential for various pharmaceutical and agricultural applications. Although several physical, chemical, and biological techniques have been reported for COSs production, it is still a challenge to obtain structurally defined COSs with defined polymerization (DP) and acetylation patterns, which hampers the specific characterization and application of COSs. Herein, we achieved the de novo production of structurally defined COSs using combinatorial pathway engineering in Bacillus subtilis. Specifically, the COSs synthase NodC from Azorhizobium caulinodans was overexpressed in B. subtilis, leading to 30 ± 0.86 mg/L of chitin oligosaccharides (CTOSs), the homo-oligomers of N-acetylglucosamine (GlcNAc) with a well-defined DP lower than 6. Then introduction of a GlcNAc synthesis module to promote the supply of the sugar acceptor GlcNAc, reduced CTOSs production, which suggested that the activity of COSs synthase NodC and the supply of sugar donor UDP-GlcNAc may be the limiting steps for CTOSs synthesis. Therefore, 6 exogenous COSs synthase candidates were examined, and the nodCM from Mesorhizobium loti yielded the highest CTOSs titer of 560 ± 16 mg/L. Finally, both the de novo pathway and the salvage pathway of UDP-GlcNAc were engineered to further promote the biosynthesis of CTOSs. The titer of CTOSs in 3-L fed-batch bioreactor reached 4.82 ± 0.11 g/L (85.6% CTOS5, 7.5% CTOS4, 5.3% CTOS3 and 1.6% CTOS2), which was the highest ever reported. This is the first report proving the feasibility of the de novo production of structurally defined CTOSs by synthetic biology, and provides a good starting point for further engineering to achieve the commercial production.

Chitosan Functionalization: Covalent and Non-Covalent Interactions and Their Characterization

Chitosan (CS) is a natural biopolymer that has gained great interest in many research fields due to its promising biocompatibility, biodegradability, and favorable mechanical properties. The versatility of this low-cost polymer allows for a variety of chemical modifications via covalent conjugation and non-covalent interactions, which are designed to further improve the properties of interest. This review aims at presenting the broad range of functionalization strategies reported over the last five years to reflect the state-of-the art of CS derivatization. We start by describing covalent modifications performed on the CS backbone, followed by non-covalent CS modifications involving small molecules, proteins, and metal adjuvants. An overview of CS-based systems involving both covalent and electrostatic modification patterns is then presented. Finally, a special focus will be given on the characterization techniques commonly used to qualify the composition and physical properties of CS derivatives.

Expression and Characterization of a Novel Cold-Adapted Chitosanase from Marine Renibacterium sp. Suitable for Chitooligosaccharides Preparation

(1) Background: Chitooligosaccharides (COS) have numerous applications due to their excellent properties. Chitosan hydrolysis using chitosanases has been proposed as an advisable method for COS preparation. Although many chitosanases from various sources have been identified, the cold-adapted ones with high stability are still rather rare but required. (2) Methods: A novel chitosanase named CsnY from marine bacterium Renibacterium sp. Y82 was expressed in Escherichia coli, following sequence analysis. Then, the characterizations of recombinant CsnY purified through Ni-NTA affinity chromatography were conducted, including effects of pH and temperature, effects of metal ions and chemicals, and final product analysis. (3) Results: The GH46 family chitosanase CsnY possessed promising thermostability at broad temperature range (0-50 °C), and with optimal activity at 40 °C and pH 6.0, especially showing relatively high activity (over 80% of its maximum activity) at low temperatures (20-30 °C), which demonstrated the cold-adapted property. Common metal ions or chemicals had no obvious effect on CsnY except Mn2+ and Co2+. Finally, CsnY was determined to be an endo-type chitosanase generating chitodisaccharides and -trisaccharides as main products, whose total concentration reached 56.74 mM within 2 h against 2% (w/v) initial chitosan substrate. (4) Conclusions: The results suggest the cold-adapted CsnY with favorable stability has desirable potential for the industrial production of COS.

Chemoenzymatic production of chitooligosaccharides employing ionic liquids and Thermomyces lanuginosus chitinase

The aim of this work was to study a two-step chemoenzymatic method for production of short chain chitooligosaccharides. Chitin was chemically pretreated using sulphuric acid, sodium hydroxide and two different ionic liquids, 1-Ethyl-3-methylimidazolium bromide and Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate under mild processing conditions. Pretreated chitin was further hydrolyzed employing purified chitinase from Thermomyces lanuginosus ITCC 8895. Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate treated chitin appeared amorphous and resulted in generation of 1.10 ± 0.89 mg ml^-1 of (GlcNAc)₂ and 1.07 ± 0.92 mg ml^-1 of (GlcNAc)₃. Further derivation of optimum conditions through two-factor-9 run experiments resulted in to 1.5 and 1.3 fold increments in (GlcNAc)₂ and (GlcNAc)₃ production, respectively. 0.1 g of both (GlcNAc)₂ and (GlcNAc)₃ has been purified from the Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate pretreated chitin (1 g) employing cation exchange chromatography. The present study will lay the foundation for development of a green sustainable solution for cost effective upcycling of coastal residual resources to chito-bioactives.

Extraction of chitin from edible crab shells of Callinectes sapidus and comparison with market purchased chitin

Chitin and its derived products have immense economic value due to their vital role in various biological activities as well as biomedical and industrial application. Insects, microorganism and crustaceans are the main supply of chitin but the crustaceans shell like shrimp, krill, lobsters and crabs are the main commercial sources. Chitin content of an individual varies depending on the structures possessing the polymer and the species. In this study edible crabs' shells (Callinectes sapidus) were demineralized and deproteinized resulting in 13.8% (dry weight) chitin recovery from chitin wastes. FTIR and XRD analyses of the experimental crude as well as purified chitins revealed that both were much comparable to the commercially purchased controls. The acid pretreatment ceded 54g of colloidal chitin that resulted in 1080% of the crude chitin. The colloidal chitin was exploited for isolation of eighty five chitinolytic bacterial isolates from different sources. Zone of clearance was displayed by the thirty five isolates (41.17%) succeeding their growth at pH 7 on colloidal chitin agar medium. Maximum chitinolytic activity i.e. 301.55 U/ml was exhibited by isolate JF70 when cultivated in extracted chitin containing both carbon and nitrogen. The study showed wastes of blue crabs can be utilized for extraction of chitin and isolation of chitinolytic bacteria that can be used to degrade chitin waste, resolve environmental pollution as well as industrial purpose.

Chitosan Oligosaccharide Production Potential of Mitsuaria sp. C4 and Its Whole-Genome Sequencing

Chitooligosaccharide is a kind of functional food, which is the degradation product of chitosan (COS) catalyzed by the endo-chitosanase (COSE) enzyme. A COSE with a molecular weight of 34 kDa was purified and characterized from a newly isolated Mitsuaria sp. C4 (C4), and a 38.46% recovery rate and 4.79-fold purification were achieved. The purified C4 COSE exhibited optimum activity at 40°C and pH 7.2 and was significantly inhibited in the presence of Cu²⁺ and Fe³⁺. The K_m and V_min of the COSE toward COS were 2.449 g/L and 0.042 g/min/L, respectively. The highest COSE activity reached 8.344 U/ml after optimizing, which represented a 1.34-fold of increase. Additionally, chitooligosaccharide obtained by COSE hydrolysis of COS was verified by using thin-layer chromatography and high-performance liquid chromatography analysis. Whole-genome sequencing demonstrated that the C4 strain contains 211 carbohydrate enzymes, our purified COSE belonging to GHs-46 involved in carbohydrate degradation. Phylogenetic analysis showed that the novel COSE obtained from the C4 strain was clustered into the degree of polymerization = two to three groups, which can perform catalysis in a similar manner to produce (GlcN)₂ and (GlcN)₃. This work indicates that the C4 strain could be a good resource for enhancing carbohydrate degradation and might represent a useful tool for chitooligosaccharide production in the functional food industry.

Improve thermostability of Bacillus sp. TS chitosanase through structure-based alignment

Chitosanases can catalyze the release of chitooligosaccharides which have a number of medical applications. Therefore, Chitosanases are good candidates for large-scale enzymatic synthesis due to their favorable thermostability properties and high catalytic efficiency. To further improve the thermostability of a chitosanase from Bacillus sp. TS, which has a half-life of 5.32 min, we mutated specific serine residues that we identified as potentially relevant through structure comparison with thermophilic CelA from Clostridium thermocellum. Out of a total of 15 mutants, three, namely S265G, S276A, and S347G, show higher thermostability. Their half-lives at 60 °C were calculated as 34.57 min, 36.79 min and 7.2 min. The K_m values of S265G, S276A and S347G mutants show substrate binding ability comparable to that of the wild-type enzyme, while the S265G mutant displays a significant decrease of enzymatic activities. Additionally, we studied the synergistic effects of combined mutations, observing that all double mutants and the triple mutant are more stable than the wild-type enzyme and single mutants. Finally, we investigated the mechanisms which might give a reasonable explanation for the improved thermostability via comparative analysis of the resulting 3D structures.

Microbial chitinases: properties, enhancement and potential applications

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

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

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

Advances in chitooligosaccharides chemical modifications

Chitooligosaccharides (COS) differ from chitosan by their molar mass: those of COS are defined to be lower than 20 kg mol^-1 . Their functionalization is widely described in the literature and leads to the introduction of new properties that broaden their application fields. Like chitosan, COS modification sites are mainly primary amine and hydroxyl groups. Among their chemical modification, one can find amidation or esterification, epoxy-amine/hydroxyl coupling, Schiff base formation, and Michael addition. When depolymerized through nitrous deamination, COS bear an aldehyde at the chain end that can open the way to other chemical reactions and lead to the synthesis of new interesting amphiphilic structures. This article details the recent developments in COS functionalization, primarily focusing on amine and hydroxyl groups and aldehyde-chain end reactions, as well as paying considerable attention to other types of modification. We also describe and compare the different functionalization protocols found in the literature while highlighting potential mistakes made in the chemical structures accompanied with suggestions. Such chemical modification can lead to new materials that are generally nontoxic, biobased, biodegradable, and usable in various applications.

Chaperone-assisted soluble expression and characterization of chitinase chiZJ408 in Escherichia coli BL21 and the chitin degradation by recombinant enzyme

The chaperone-assisted soluble expression and characterization of high molecular weight chitinase chiZJ408 in Escherichia coli BL21 were investigated. Chitin degradation products by chitinase chiZJ408 were analyzed. The results indicated that the introduction of the chaperone GroELS promoted the correct folding of chitinase chiZJ408 and increased its soluble expression by 14.9% (p < 0.05) in E. coli BL21. The optimal pH and temperature of chitinase chiZJ408 were respectively 6.0 and 50 °C. Chitinase chiZJ408 was stable at pHs of 4.0 ∼ 7.0 and at below 40 °C. Mg²⁺and Ca²⁺ had a significant impact on improving the activity of chitinase chiZJ408. Chitinase chiZJ408 was demonstrated to be exochitinase that cleaved the β-1,4-glycosidic bond of the chitin chain to generate only N,N'-diacetylchitobiose. This study broadens our understanding of chitinase and provides a basis for solving the problem of inclusion body formed by long fragment gene expression in E. coli.

Evaluation of antibacterial, teratogenicity and antibiofilm effect of sulfated chitosans extracted from marine waste against microorganism

Biofilms play a key role in infectious diseases, as they may form on the surface and persist after treatment with various antimicrobial agents. The Staphylococcus aureus, Klebsiella pneumoniae, S. typhimurium, P. aeruginosa, and Escherichia coli most frequently associated with medical devices. Chitosan sulphate from marine litter (SCH-MW) was extracted and the mineral components were determined using atomic absorption spectroscopy (AAS). The degree of deacetylation (DA) of SCH was predicted 50% and 33.3% in crab and shrimp waste respectively. The elucidation of the structure of the SCH-MW was portrayed using FT-IR and 1H-NMR spectroscopy. The molecular mass of SCH-MW was determined with Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF). The teratogenicity of SCH-MW was characterized by the zebrafish embryo (ZFE) model. Antimicrobial activity of SCH-MW was tested with the agar well diffusion method; the inhibitory effect of SCH-MW on biofilm formation was assessed in 96 flat well polystyrene plates. The result revealed that a low concentration of crab-sulfated chitosan inhibited bacterial growth and significantly reduced the anti-biofilm activity of gram-negative and gram-positive bacteria relatively to shrimp. It is potentially against the biofilm formation of pathogenic bacteria.

Differential expression of bio-active metabolites produced by chitosan polymers-based Bacillus amyloliquefaciens fermentation

Bacillus amyloliquefaciens strain PPL shows a potential for the control of phytopathogenic fungi. In the present study, upon growing the strain PPL on various forms of chitosan (0.5 % powder, 0.1 % soluble, and 0.15 % colloidal) as the carbon source, the antifungal activity on tomato Fusarium wilt correlated with the activity of chitosanase and β-1,3-glucanase. The colloidal substrate-based strain PPL fermentation displayed the highest degree of spore germination inhibition (79.5 %) and biocontrol efficiency (76.0 %) in tomato by increased biofilm formation. The colloidal culture upregulated the expression of chitosanase gene (5.9-fold), and the powder attributed to the expression of cyclic lipopeptides-genes (2.5-5.7 fold). Moreover, the three chitosan cultures induced the morphological changes of Fusarium oxysporum. These results suggest that the choice of growth substrate synergistically affects the production of secondary metabolites by PPL strain, and consequently its antifungal activity.

Ultrabroad-spectrum, multidrug resistant bacteria-killing, and biocompatible quaternized chitin derivative for infected wound healing

Wound infections have consistently been recognized as serious threats to human. The design of antimicrobial and biocompatible wound dressings for infected wounds is an area of constant research. Herein, we homogeneously synthesized an ultrabroad-spectrum antimicrobial and biocompatible quaternized chitin derivative (QC-4) in a high-efficiency and sustainable route using aqueous KOH/urea solution. Particularly, QC-4 displayed powerful multidrug resistant bacteria-killing activities even at a very low antimicrobial concentration range from 500 ng/mL to 5 μg/mL, including clinically prevalent multidrug-resistant Escherichia coli (MDR-E. coli), methicillin resistant Staphylococcus aureus (MRSA), multidrug-resistant Pseudomonas aeruginosa (MRPA), and multidrug-resistant Acinetobacter baumannii (MDR-A. baumannii). With the aim to facilitate clinical translation, we validated the biocompatibility and safety of QC-4 both in vitro and in vivo, and further assessed the effects of QC-4 on infected wound healing in a porcine infectious full-thickness skin wound model. QC-4 demonstrated significant reduction of microbial aggregates and enhanced wound-healing effects by promoted re-epithelialization and collagen deposition, which were quite comparable to that of commercial Alginate-Ag dressing and absolutely superior to commercial Chitoclot Bandage dressing. Additionally, we provided clear evidences that QC-4 had a unique mechanism of action by attracting electrostatically to the negatively charged microbial surface, thus damaging the microbial cell wall and membrane. Findings of this work provided robust preclinical rationale for the future translational applications of QC-4 as a novel ultrabroad-spectrum and multidrug resistant bacteria-killing antimicrobial wound dressing for clinical wound management.

Antiviral activity by lecithin-induced fengycin lipopeptides as a potent key substrate against Cucumber mosaic virus

In this study, the effect of different growth substrates on the production of biosurfactants in the PPL strain of Bacillus amyloliquefaciens-a biocontrol agent for diseases affecting pepper and tomato plants-and on the antiviral effect of the PPL strain on Cucumber mosaic virus (CMV)-infected pepper plants was investigated. The multifunctional PPL strain exhibited enhanced growth and increased production of biosurfactants upon lecithin supplementation and consequently exhibited potent anti-CMV activity. The enhanced anti-CMV activity of the lecithin-supplemented PPL culture could be attributed to the antiviral effect as well as to the upregulation of plant defense-related genes. Treatment with pure commercial fengycins elicited a defense response against CMV in pepper plants; this effect was similar to that observed upon treatment with the lecithin-supplemented PPL culture. To the best of our knowledge, this is the first study to report the antiviral activity of lecithin-induced fengycin lipopeptides. These results suggest that the growth substrate affects antimicrobial production by B. amyloliquefaciens PPL, and consequently its antiviral activity.

The impact of chitooligosaccharides and their derivatives on the in vitro and in vivo antitumor activity: A comprehensive review

Chitooligosaccharides (COS) are the degraded products of chitin or chitosan. COS is water-soluble, non-cytotoxic to organisms, readily absorbed through the intestine, and eliminated primarily through the kidneys. COS possess a wide range of biological activities, including immunomodulation, cholesterol-lowering, and antitumor activity. Although work on COS goes back at least forty years, several aspects remain unclear. This review narrates the recent developments in COS antitumor activities, while paying considerable attention to the impacts of physicochemical properties (such as molecular weight and degrees of deacetylation) and chemical modifications both in vitro and in vivo. COS derivatives not only improve some physicochemical properties, but also expand the range of applications in drug and gene delivery. COS (itself or as a drug carrier) can inhibit tumor cell proliferation and metastasis, which might be attributed to its ability to stimulate the immune response along with its anti-angiogenic activity. Further, an attempt has been made to report limitations and future research. The potential health benefits of COS and its derivatives against cancer may offer a new insight on their applications in food and medical fields.

Chitosan and Derivatives: Bioactivities and Application in Foods

Chitosan is a biodegradable, biocompatible, and nontoxic aminopolysaccharide. This review summarizes and discusses the structural modifications, including substitution, grafting copolymerization, cross-linking, and hydrolysis, utilized to improve the physicochemical properties and enhance the bioactivity and functionality of chitosan and related materials. This manuscript also reviews the current progress and potential of chitosan and its derivatives in body-weight management and antihyperlipidemic, antihyperglycemic, antihypertensive, antimicrobial antioxidant, anti-inflammatory, and immunostimulatory activities as well as their ability to interact with gut microbiota. In addition, the potential of chitosan and its derivatives as functional ingredients in food systems, such as film and coating materials, and delivery systems is discussed. This manuscript aims to provide up-to-date information to stimulate future discussion and research to promote the value-added utilization of chitosan in improving the safety, quality, nutritional value and health benefits, and sustainability of our food system while reducing the environmental hazards.