Multiple strategies to improve the yield of chitinase a from Bacillus licheniformis in Pichia pastoris to obtain plant growth enhancer and GlcNAc

Identification, heterologous expression and characterization of a new unspecific peroxygenase from Marasmius fiardii PR-910

Unspecific peroxygenases (UPOs) are glycosylated enzymes that provide an efficient method for oxyfunctionalizing a variety of substrates using only hydrogen peroxide (H2O2) as the oxygen donor. However, their poor heterologous expression has hindered their practical application. Here, a novel UPO from Marasmius fiardii PR910 (MfiUPO) was identified and heterologously expressed in Pichia pastoris. By employing a two-copy expression cassette, the protein titer reached 1.18 g L-1 in a 5 L bioreactor, marking the highest record. The glycoprotein rMfiUPO exhibited a smeared band in the 40 to 55 kDa range and demonstrated hydroxylation, epoxidation and alcohol oxidation. Moreover, the peroxidative activity was enhanced by 150% after exposure to 50% (v/v) acetone for 40 h. A semi-preparative production of 4-OH-β-ionone on a 100 mL scale resulted in a 54.2% isolated yield with 95% purity. With its high expression level, rMfiUPO is a promising candidate as an excellent parental template for enhancing desirable traits such as increased stability and selectivity through directed evolution, thereby meeting the necessary criteria for practical application.

Biochemical Properties of a Cold-Active Chitinase from Marine Trichoderma gamsii R1 and Its Application to Preparation of Chitin Oligosaccharides

The enzymatic degradation of different chitin polymers into chitin oligosaccharides (COSs) is of great significance given their better solubility and various biological applications. Chitinase plays a pivotal role in the enzymatic preparation of COSs. Herein, a cold-adapted and efficient chitinase (ChiTg) from the marine Trichoderma gamsii R1 was purified and characterized. The optimal temperature of ChiTg was 40 °C, and the relative activity at 5 °C was above 40.1%. Meanwhile, ChiTg was active and stable from pH 4.0 to 7.0. As an endo-type chitinase, ChiTg exhibited the highest activity with colloidal chitin, then with ball-milled and powdery chitin. In addition, ChiTg showed high efficiency when hydrolyzing colloidal chitin at different temperatures, and the end products were mainly composed of COSs with one to three degrees of polymerization. Furthermore, the results of bioinformatics analysis revealed that ChiTg belongs to the GH18 family, and its acidic surface and the flexible structure of its catalytic site may contribute to its high activity in cold conditions. The results of this study provide a cold-active and efficient chitinase and ideas for its application regarding the preparation of COSs from colloidal chitin.

The synergistic action of two chitinases from Vibrio harveyi on chitin degradation

In this study, two chitinases (VhChit2 and VhChit6) from Vibrio harveyi possessed specific activity of 36.5 and 20.8 U/mg, respectively. Structure analysis indicates that their amino acid composition of active sites is similar, but the substrate binding cleft of VhChit2 is deeper than that of VhChit6. They were shown to have a synergistic effect on chitin degradation, and the optimized degree of synergy and the degradation ratio of chitin reached 1.75 and 23.6 %, respectively. The saturated adsorption capacity of VhChit2 and VhChit6 adsorbed in 1 g of chitin was 48.5 and 33.4 mg. It was found that VhChit2 and VhChit6 had different adsorption sites on chitin, making more enzymes absorbed by chitin. Furthermore, the combined use of VhChit2 and VhChit6 increased their binding force of chitinases with the substrate. The synergistic action of VhChit2 and VhChit6 may be attributed to their different adsorption sites on chitin and the increased binding force with chitin.

Characterization of chitinases from the GH18 gene family in the myxomycete Physarum polycephalum

BACKGROUND

Physarum polycephalum is an unusual macroscopic myxomycete expressing a large range of glycosyl hydrolases. Among them, enzymes from the GH18 family can hydrolyze chitin, an important structural component of the cell walls in fungi and in the exoskeleton of insects and crustaceans.

METHODS

Low stringency sequence signature search in transcriptomes was used to identify GH18 sequences related to chitinases. Identified sequences were expressed in E. coli and corresponding structures modelled. Synthetic substrates and in some cases colloidal chitin were used to characterize activities.

RESULTS

Catalytically functional hits were sorted and their predicted structures compared. All share the TIM barrel structure of the GH18 chitinase catalytic domain, optionally fused to binding motifs, such as CBM50, CBM18, and CBM14, involved in sugar recognition. Assessment of the enzymatic activities following deletion of the C-terminal CBM14 domain of the most active clone evidenced a significant contribution of this extension to the chitinase activity. A classification based on module organization, functional and structural criteria of characterized enzymes was proposed.

CONCLUSIONS

Physarum polycephalum sequences encompassing a chitinase like GH18 signature share a modular structure involving a structurally conserved catalytic TIM barrels decorated or not by a chitin insertion domain and optionally surrounded by additional sugar binding domains. One of them plays a clear role in enhancing activities toward natural chitin.

GENERAL SIGNIFICANCE

Myxomycete enzymes are currently poorly characterized and constitute a potential source for new catalysts. Among them glycosyl hydrolases have a strong potential for valorization of industrial waste as well as in therapeutic field.

Recombinant expression of hen egg white lysozyme with the assistance of xylanase fusion partner in Pichia pastoris

Due to its bacteriolytic activity, hen egg white lysozyme (HEWL) is widely used in the feed, food, and pharmaceutical industries. However, its application is hindered by low protein expression levels in microbial expression systems. In this work, a novel fusion protein expression strategy was proposed for increasing the expression level of HEWL. First, HEWL, fused with a highly expressed fusion protein partner xylanase XynCDBFV, is expressed in Pichia pastoris. Secondly, a linker including endogenous protease cleavage sites was introduced between two fusion proteins in order to separate them directly during the secretion process. Finally, the results show that the supernatant of XynCDBFV-HEWL has a higher HEWL expression level and activity compared with HEWL only. It should be noted that the expression of HEWL reaches to about 3.5 g/L, and the activity of HEWL against Micrococcus lysodeikticus reaches to 1.50 × 10⁵ U/mL in a fed-batch fermentation, which is currently the highest level of recombinant expression of an egg white-derived lysozyme. Taken together, we acquired bioactive HEWL for large-scale recombinant production in Pichia pastoris using a novel fusion protein expression strategy, which could then be used for a variety of applications.

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.

High-Level Extracellular Expression of a New β-N-Acetylglucosaminidase in Escherichia coli for Producing GlcNAc

N-acetyl-β-D glucosamine (GlcNAc) is wildly used in cosmetics, nutraceuticals and pharmaceuticals. The traditional chemical process for GlcNAc production from chitin causes serious acidic pollution. Therefore, the enzymatic hydrolysis becomes a great promising and alternative strategy to produce GlcNAc. β-N-acetylglucosaminidase (NAGase) can hydrolyze chitin to produce GlcNAc. Here, a GH3 family NAGase encoding gene BlNagZ from Bacillus licheniformis was expressed extracellularly in Escherichia coli guided by signal peptide PelB. The recombinant BlNagZ presented the best activity at 60°C and pH 5.5 with a high specific activity of 13.05 U/mg. The BlNagZ activity in the fermentation supernatant can reach 13.62 U/mL after optimizing the culture conditions, which is 4.25 times higher than optimization before. Finally, combining BlNagZ with chitinase ChiA we identified before, chitin conversion efficiency to GlcNAc can reach 89.2% within 3.5 h. In all, this study provided not only a high active NAGase, and a secreted expression strategy to reduce the cost of production, which is conducive to the industrial application.