Solubility-based Separation and Purification of Long-Chain Chitin Oligosaccharides with an Organic-Water Mixed Solvent

Recombinant expression and characterization of the endochitinase Chit36-TA from Trichoderma asperellum in Komagataella phaffii for chitin degradation of black soldier fly exuviae

The natural polymer chitin is an abundant source for valuable N-acetylchitooligosaccharides and N-acetylglucosamine applicable in several industries. The endochitinase Chit36-TA from Trichoderma asperellum was recombinantly expressed in Komagataella phaffii for the enzymatic degradation of chitin from unused insect exuviae into N-acetylchitooligosaccharides. Chit36-TA was purified by Ni-NTA affinity chromatography and subsequently biochemically characterized. After deglycosylation, the endochitinase had a molecular weight of 36 kDa. The optimum pH for Chit36-TA was 4.5. The temperature maximum of Chit36-TA was determined to be 50 °C, while it maintained > 93% activity up to 60 °C. The chitinase was thermostable up to 45 °C and exhibited ~ 50% activity after a 15 min incubation at 57 °C. Chit36-TA had a maximum specific enzyme activity of 50 nkat/mg with a Km value of 289 µM with 4-methylumbelliferyl-N,N',N″-triacetyl-β-chitotrioside as substrate. Most tested cations, organic solvents and reagents were well-tolerated by the endochitinase, except for SDS (1 mM), Cu2+ (10 mM) and Mn2+ (10 mM), which had stronger inhibitory effects with residual activities of 3, 41 and 28%, respectively. With a degree of hydrolysis of 32% applying colloidal shrimp chitin (1% (w/v)) and 12% on insect larvae (1% (w/v)) after 24 h, the endochitinase was found to be suitable for the conversion of colloidal chitin as well as chitin from black soldier fly larvae into water-soluble N-acetylchitooligosaccharides. To prove scalability, a bioreactor process was developed in which a 55-fold higher enzyme activity of 49 µkat/l and a tenfold higher protein expression of 1258 mg/l were achieved.

Chitosan oligosaccharides exert neuroprotective effects via modulating the PI3K/Akt/Bcl-2 pathway in a Parkinsonian model

Parkinson's disease (PD), the second most common neurodegenerative disease, is a threat to patients due to the inability to prevent or decelerate disease progression. Currently, most clinical drugs for the treatment of PD are synthetic drugs that always present undesirable adverse or toxic effects. Chitosan oligosaccharide (COS) is a natural oligosaccharide that has been considered relatively safe and studied in the therapeutic effects on different types of neuronal disorders. In this study, we separated four COS monomers (COSs) including chitobiose (COS2), chitotriose (COS3), chitotetraose (COS4) and chitopentaose (COS5) to explore their structure-activity relationship in PD mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Techniques including TLC, HPLC, MS, and NMR were applied to investigate the purity and structure of the COSs. After the oral administration of COSs, behavior indexes, pathological indexes, cytokines, and expression of proteins in the nigrostriatal pathway of the mice were analyzed. The results showed that the four COSs were fully deacetylated and the purity was >90%. Additionally, the neurobehavioral deficits of the PD mice were improved by treatment with COSs. The results further proved that COSs could protect the TH-labelled dopaminergic neurons via reducing the overexpression of α-synuclein, alleviating neuroinflammation, and activating the PI3K/Akt/Bcl-2 pathway to reduce apoptosis. COS3 exhibited a better effect on protecting dopaminergic neurons; however, COS2 provided a better effect on reducing the overexpression of α-synuclein. To conclude, the neuroprotective activity makes COSs a viable candidate as an ingredient for healthcare products.

Advances in the preparation and assessment of the biological activities of chitosan oligosaccharides with different structural characteristics

Chitosan oligosaccharides (COSs) are widely used biopolymers that have been studied in relation to a variety of abnormal biological activities in the food and biomedical fields. Since different COS preparation technologies produce COS compounds with different structural characteristics, it has not yet been possible to determine whether one or more chito-oligomers are primarily responsible for the bioactivity of COSs. The inherent biocompatibility, mucosal adhesion and nontoxic nature of COSs are well documented, as is the fact that they are readily absorbed from the intestinal tract, but their structure-activity relationship requires further investigation. This review summarizes the methods used for COS preparation, and the research findings with regard to the antioxidant, anti-inflammatory, anti-obesity, bacteriostatic and antitumour activity of COSs with different structural characteristics. The correlation between the molecular structure and bioactivities of COSs is described, and new insights into their structure-activity relationship are provided.

Short-Chain Cello-oligosaccharides: Intensification and Scale-up of Their Enzymatic Production and Selective Growth Promotion among Probiotic Bacteria

Short-chain cello-oligosaccharides (COS; degree of polymerization, DP ≤ 6) are promising water-soluble dietary fibers. An efficient approach to their bottom-up synthesis is from sucrose and glucose using glycoside phosphorylases. Here, we show the intensification and scale up (20 mL; gram scale) of COS production to 93 g/L product and in 82 mol % yield from sucrose (0.5 M). The COS were comprised of DP 3 (33 wt %), DP 4 (34 wt %), DP 5 (24 wt %), and DP 6 (9 wt %) and involved minimal loss (≤10 mol %) to insoluble fractions. After isolation (≥95% purity; ≥90% yield), the COS were examined for growth promotion of probiotic strains. Benchmarked against inulin, trans-galacto-oligosaccharides, and cellobiose, COS showed up to 4.1-fold stimulation of cell density for Clostridium butyricum, Lactococcus lactis subsp. lactis, Lactobacillus paracasei subsp. paracasei, and Lactobacillus rhamnosus but were less efficient with Bifidobacterium sp. This study shows the COS as selectively functional carbohydrates with prebiotic potential and demonstrates their efficient enzymatic production.

Chitoheptaose Promotes Heart Rehabilitation in a Rat Myocarditis Model by Improving Antioxidant, Anti-Inflammatory, and Antiapoptotic Properties

Background

Myocarditis is one of the important causes of dilated cardiomyopathy, cardiac morbidity, and mortality worldwide. Chitosan oligosaccharides (COS) may have anti-inflammatory and cardioprotective effects on myocarditis. However, the exact molecular mechanism for the effects of functional COS on myocarditis remains unclear.

Methods

Anti-inflammatory activities of COS (chitobiose, chitotriose, chitotetraose, chitopentaose, chitohexaose, chitoheptaose, and chitooctaose) were measured in lipopolysaccharide- (LPS-) stimulated RAW264.7 cells. A rat model with myocarditis was established and treated with chitopentaose, chitohexaose, chitoheptaose, and chitooctaose. Serum COS were measured by using high-performance liquid chromatography (HPLC) in all rats. Myocarditis injury, the levels of reactive oxygen species (ROS), reactive nitrogen species (RNS), inflammatory factors, and apoptotic factors were also measured. Pearson's correlation coefficient test was used to explore the relationship between the levels of ROS/RNS and cardiac parameters.

Results

Among all chitosan oligosaccharides, the COS > degrees of polymerization (DP) 4 showed anti-inflammatory activities (the activity order was chitopentaose<chitohexaose<chitoheptaose<chitooctaose) by reducing the levels of interleukin- (IL-) 1β, IL-17A, and interferon- (IFN-) γ and increasing the level of IL-10. However, the serum level of chitooctaose was low whereas it showed significant therapeutic effects on myocarditis by improving cardiac parameters (left ventricular internal dimension, both end-systolic and end-diastolic, ejection fraction, and fractional shortening), inflammatory cytokines (IL-1β, IL-10, IL-17A, and IFN-γ), oxidative factors (ROS and RNS), and apoptotic factors (caspase 3, BAX, and BCL-2) when compared with chitopentaose, chitohexaose, and chitooctaose (COS DP > 4). The levels of ROS/RNS had a strong relationship with cardiac parameters.

Conclusions

Chitoheptaose plays a myriad of cardioprotective roles in the myocarditis model via its antioxidant, anti-inflammatory, and antiapoptotic activities.

Three-Enzyme Phosphorylase Cascade for Integrated Production of Short-Chain Cellodextrins

Cellodextrins are linear β-1,4-gluco-oligosaccharides that are soluble in water up to a degree of polymerization (DP) of ≈6. Soluble cellodextrins have promising applications as nutritional ingredients. A DP-controlled, bottom-up synthesis from expedient substrates is desired for their bulk production. Here, a three-enzyme glycoside phosphorylase cascade is developed for the conversion of sucrose and glucose into short-chain (soluble) cellodextrins (DP range 3-6). The cascade reaction involves iterative β-1,4-glucosylation of glucose from α-glucose 1-phosphate (αGlc1-P) donor that is formed in situ from sucrose and phosphate. With final concentration and yield of the soluble cellodextrins set as targets for biocatalytic synthesis, three major factors of reaction efficiency are identified and partly optimized: the ratio of enzyme activity, the ratio of sucrose and glucose, and the phosphate concentration used. The efficient use of the phosphate/αGlc1-P shuttle for cellodextrin production is demonstrated and the soluble product at 40 g L^-1 is obtained under near-complete utilization of the donor substrate offered (88 mol% from 200 mm sucrose). The productivity is 16 g (L h)^-1 . Through a simple two-step route, the soluble cellodextrins are recovered from the reaction mixture in ≥95% purity and ≈92% yield. Overall, this study provides the basis for their integrated production.

SEC Separation of Polysaccharides Using Macroporous Spherical Silica Gel as a Stationary Phase

Abstract

Meso- and macroporous spherical silica gels of pore sizes in the range of 60–1000 Å and 40–75 µm particle size were investigated as a stationary phase for the separation and purification of polysaccharides and poly(ethylene glycols) (PEGs) of various MWs using an aqueous mobile phase. Sephadex and Bio-Gel were used for comparison as the most common stationary phases for similar purposes. The separation of dextrans of a mean MW = 31 kDa from small molecules (NaCl) was possible with SiO₂ with a pore size of 60–300 Å, but the observed efficiencies of a column of the same size were lower comparing with Sephadex or Bio-Gel. In the case of oxidized alginic acid only SiO₂ of the 60 Å pore size was suitable, while Sephadex, Bio-Gel and other investigated silicas were not efficient. Sephadex and 300–1000 Å SiO₂ offered the possibility of dividing dextrans with MW within the range of 1 MDa–10 kDa into fractions of various MWs, while Bio-Gel and 60 Å SiO₂ were not suitable. The investigated silica gels strongly adsorbed PEGs of MW 2–20 kDa. The amount adsorbed decreased with the increase of pore size and they were not useful as a stationary phase for this class of polymers. An advantage of SiO₂ of the investigated particle size was a very low back pressure comparing with Sephadex. A considerably lower price of silica offers time- and cost-efficient separation of polysaccharides.

Graphical Abstract