Hydrogen peroxide pretreatment efficiently assisting enzymatic hydrolysis of chitosan at high concentration for chitooligosaccharides

A review on the biological activities and the nutraceutical potential of chitooligosaccharides

Chitooligosaccharides (CHOS) or chitosan oligosaccharides (COS) are oligomers mainly composed of d-glucosamine (GlcN) units and structured in a positively charged, basic, amino molecule obtained from the degradation of chitin/chitosan through physical, chemical, or enzymatic methods. CHOS display physicochemical properties attractive to applications from the food to the biomedical field, such as non-toxicity to humans, high water solubility, low viscosity, biocompatibility, and biodegradability. These properties also allow CHOS to exert important biological activities, for example, antioxidant, antimicrobial, anti-inflammatory, immunomodulatory, antitumor, and hypocholesterolemic ones, besides to exhibit applications in food systems, technological, and nutraceutical potential. Therefore, this study summarized the synthesis and chemical structure, biological functions, and mechanisms of action of CHOS; with this, we aimed to contribute to the knowledge about the application of CHOS from the food to the biomedical industries.

Recent trends in the separation and analysis of chitooligomers

Chitosan is a widely used linear biopolymer composed mainly of glucosamine and to a lesser extent of N-acetylglucosamine units. Many biological activities of chitosan are attributed to its shorter oligomeric chains, which consist of chitosan prepared either by enzyme activity (lysozyme, bacterial chitinase) or chemically by acid-catalyzed hydrolysis (e.g. in the stomach). However, these processes always result in a mixture of shorter chitooligosaccharides with varying degrees of acetylation whereas for relevant results of biological studies it is necessary to work with a precisely defined material. In this review, we provide an overview and comparison of analytical methods leading to the determination of the degree of polymerization (DP), the degree of acetylation (DA), the fraction of acetylation (FA) and the acetylation patterns (PA) of chitooligosaccharide chains and of the current state of knowledge on chitooligosaccharide separation. This review aims to present the most promising routes to well-defined low molecular weight chitosan with low dispersity.

Grafting chlorogenic acid enhanced the antioxidant activity of curdlan oligosaccharides and modulated gut microbiota

In this study, the effects of grafting chlorogenic acid (CA) on the antioxidant and probiotic activities of curdlan oligosaccharides (CDOS) were investigated. CDOS with degrees of polymerization of 3-6 was first obtained by degradation of curdlan with hydrogen peroxide and then grafted with CA using a free radical-mediated method under an ultrasonication-assisted Fenton system. The thermal stability and antioxidant ability of CDOS were enhanced after grafting with CA. In vitro fermentation, supplementation of CDOS-CA stimulated the proliferation of Prevotella and Faecalibacterium while inhibiting the growth of harmful microbiota. Notably, the concentration of total short-chain fatty acids and the relative abundance of beneficial bacteria markedly increased after fermentation of CDOS-CA, indicating that CA grafting could improve the probiotic activity of CDOS. Overall, the covalent binding of CDOS and CA could enhance the antioxidant and probiotic activities of CDOS, suggesting potential improvements in gastrointestinal and colonic health.

Chitooligosaccharide and Its Derivatives: Potential Candidates as Food Additives and Bioactive Components

Chitooligosaccharide (CHOS), a depolymerized chitosan, can be prepared via physical, chemical, and enzymatic hydrolysis, or a combination of these techniques. The superior properties of CHOS have attracted attention as alternative additives or bioactive compounds for various food and biomedical applications. To increase the bioactivities of a CHOS, its derivatives have been prepared via different methods and were characterized using various analytical methods including FTIR and NMR spectroscopy. CHOS derivatives such as carboxylated CHOS, quaternized CHOS, and others showed their potential as potent anti-inflammatory, anti-obesity, neuroprotective, and anti-cancer agents, which could further be used for human health benefits. Moreover, enhanced antibacterial and antioxidant bioactivities, especially for a CHOS-polyphenol conjugate, could play a profound role in shelf-life extension and the safety assurance of perishable foods via the inhibition of spoilage microorganisms and pathogens and lipid oxidation. Also, the effectiveness of CHOS derivatives for shelf-life extension can be augmented when used in combination with other preservative technologies. Therefore, this review provides an overview of the production of a CHOS and its derivatives, as well as their potential applications in food as either additives or nutraceuticals. Furthermore, it revisits recent advancements in translational research and in vivo studies on CHOS and its derivatives in the medical-related field.

Preparation of water-soluble chitosan oligosaccharides by oxidative hydrolysis of chitosan powder with hydrogen peroxide

Chitosan (CS) is only soluble in weak acid medium, thereby limiting its wide utilisation in the field of biomedicine, food, and agriculture. In this report, we present a method for preparing water-soluble CS oligosaccharides (COSs) at high concentration (∼10%, w/v) via the oxidative hydrolysis of CS powder with molecular weight (Mw) ∼90,000 g/mol) in 2% H2O2 solution at ambient temperature by a two-step process, namely, the heterogeneous hydrolysis step and homogeneous hydrolysis step. The resultant COSs were characterised by gel permeation chromatography (GPC), fourier transforms infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), proton nuclear magnetic resonance spectroscopy (1H NMR) and X-ray diffraction (XRD) spectroscopy. The resulting products were composed of COSs (Mw of 2000-6600 g/mol) that were completely soluble in water. The results also indicated that the structure of COSs was almost unchanged compared with the original CS unless Mw was low. Accordingly, COSs with low Mw (∼2000 g/mol) and high concentration (10%, w/v) could be effectively prepared by the oxidative hydrolysis of CS powder using hydrogen peroxide under ambient conditions.

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.

Preparation and antibacterial effect of chitooligosaccharides monomers with different polymerization degrees from crab shell chitosan by enzymatic hydrolysis

This study aimed to explore the structure and antibacterial properties of chitooligosaccharide monomers with different polymerization degrees and to provide a theoretical basis for inhibiting Salmonella infection. Chitosan was used as a raw material to prepare and separate low-molecular-weight chitooligosaccharides. Chitobiose, chitotriose, and chitotetraose were obtained by gradient elution with cation exchange resin. The molecular weights and acetyl groups of the three monomers were determined by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and nuclear magnetic resonance (NMR), respectively. Three chitooligosaccharide monomers were used to explore the antibacterial effect on Salmonella. The results showed that the degree of deacetylation of chitosan was 92.6%, and the enzyme activity of chitosanase was 102.53 U/g. Within 18 h, chitosan was enzymatically hydrolyzed to chitooligosaccharides containing chitobiose, chitotriose, and chitotetraose, which were analyzed by thin-layer chromatography (TLC) and MALDI-TOF. MALD-TOF and TLC showed that the separation of monomers with ion exchange resins was effective, and NMR showed that there was no acetyl group. Chitobiose had a poor inhibitory effect on Salmonella, and chitotriose and chitotetraose had equivalent antibacterial effects.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Evaluation of Antibacterial and Antifungal Properties of Low Molecular Weight Chitosan Extracted from Hermetia illucens Relative to Crab Chitosan

This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (Mw) of 6-21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan's origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.

Characterization of Different Salt Forms of Chitooligosaccharides and Their Effects on Nitric Oxide Secretion by Macrophages

In this paper, chitooligosaccharides in different salt forms, such as chitooligosaccharide lactate, citrate, adipate, etc., were prepared by the microwave method. They were characterized by SEM, FTIR, NMR, etc., and the nitric oxide (NO) expression was determined in RAW 264.7 cells. The results showed that pure chitooligosaccharide was an irregular spherical shape with rough surface, and its different salt type products are amorphous solid with different honeycomb sizes. In addition to the characteristic absorption peaks of chitooligosaccharides, in FTIR, the characteristic absorption of carboxyl group, methylene group, and aromatic group in corresponding acid appeared. The characteristic absorption peaks of carbon in carboxyl group, hydrogen and carbon in methyl, methylene group, and aromatic group in corresponding acid also appeared in NMR. Therefore, the sugar ring structure and linking mode of chitooligosaccharides did not change after salt formation of chitooligosaccharides. Different salt chitooligosaccharides are completely different in promoting NO secretion by macrophages, and pure chitooligosaccharides are the best.

Increasing chitosanase production in Bacillus cereus by a novel mutagenesis and screen method

Chitosan hydrolysis by chitosanase is one of the most effective methods to produce chitosan oligosaccharides. One of the prerequisites of enzyme fermentation production is to select and breed enzyme-producing cells with good performance. So in the process of fermentation production, the low yield of chitosanase cannot meet the current requirement. In this paper, a strain producing chitosanase was screened and identified, and a novel mutagenesis system (Atmospheric and Room Temperature Plasma (ARTP)) was selected to increase the yield of chitosanase. Then, the fermentation medium was optimized to further improve the enzyme activity of the strain. A strain of Bacillus cereus capable of producing chitosanase was screened and identified from soil samples. A mutant strain of B.cereus was obtained by Atmospheric and Room Temperature Plasma mutagenesis and bioscreening method, and chitosanase activity was 2.49 folds that of the original bacterium. After an optimized fermentation medium, the enzyme activity of the mutant strain was 1.47 folds that of the original bacterium. Combined with all the above optimization experiments, the enzyme activity of mutant strain increased by 3.66 times. The results showed that the Atmospheric and Room Temperature Plasma mutagenesis and bioscreening method could significantly increase the yield of chitosanase in B.cereus, and had little effect on the properties of the enzyme. These findings have potential applications in the mutagenesis of other enzyme-producing microorganisms.

Identification of low molecular weight degradation products from chitin and chitosan by electrospray ionization time-of-flight mass spectrometry

The beneficial effects provided by chitosan oligosaccharides (COS) make them of interest in medical research. The monomers that constitute COS confer distinct properties, so controlling COS composition during their production is significant. In this work, we degraded chitin and chitosan polymers and identified low molecular weight products such as COS that formed, using electrospray ionization time-of-flight mass spectrometry. Our results show that hydrochloric acid, hydrogen peroxide, and nitrous acid generate distinct products from chitin and chitosan. Hydrochloric acid degrades chitin and chitosan to produce glucosamine (GlcN) monomers and oligomers. Hydrogen peroxide degrades chitosan to produce GlcN and N-acetyl-d-glucosamine (GlcNAc) monomers and oligomers, and nitrous acid degrades chitosan to produce 2,5-anhydro- d-mannose. Our studies show that COS composition is dictated by both the degradation protocol and the starting polymer. Additionally, our results enable selection of degradation protocols based on their ability to degrade chitin and chitosan and facilitate the production of COS with desired compositions.

Effect of molecular weight of chitosan and its oligosaccharides on antitumor activities of chitosan-selenium nanoparticles

The antitumor activity of zero-valent selenium (Se⁰) nanoparticles stabilized by chitosan and its oligosaccharides having molecular weights 3 k, 65 k, and 600 k Da, was investigated. The nanoparticles stabilized with high molecular weight chitosan not only released selenium more easily compared with low molecular weight chitosan, but were also taken up by HepG2 cells more easily through electrostatic effect. Moreover, these were more efficient in inhibiting HepG2 cell viability. High ROS levels of cancer cells could easily induce selenium release from these nanoparticles, and oxidize the less toxic Se⁰ to highly toxic Se⁴⁺. The latter could not only consume antioxidant enzymes, but also cause mitochondrial dysfunction and cell apoptosis. Study of antitumor efficacy and side effect on a HepG2 xenograft BALB/c nude mice model exhibited that CS-Se⁰NPs had a higher selectivity for cancer cells; however, their effect on normal cells, which have relatively lower ROS levels, was limited.