Characteristics of a recombinant Fusarium verticillioides cutinase and its effects on enzymatic hydrolysis of rice straw

Functional characterization and structural insights of three cutinases from the ascomycete Fusarium verticillioides

Cutinases are serine esterases that belong to the α/β hydrolases superfamily. The natural substrates for these enzymes are cutin and suberin, components of the plant cuticle, the first barrier in the defense system against pathogen invasion. It is well-reported that plant pathogens produce cutinases to facilitate infection. Fusarium verticillioides, one important corn pathogens, is an ascomycete upon which its cutinases are poorly explored. Consequently, the objective of this study was to perform the biochemical characterization of three precursor cutinases (FvCut1, FvCut2, and FvCut3) from F. verticillioides and to obtain structural insights about them. The cutinases were produced in Escherichia coli and purified. FvCut1, FvCut2, and FvCut3 presented optimal temperatures of 20, 40, and 35 °C, and optimal pH of 9, 7, and 8, respectively. Some chemicals stimulated the enzymatic activity. The kinetic parameters revealed that FvCut1 has higher catalytic efficiency (Kcat/Km) in the p-nitrophenyl-butyrate (p-NPB) substrate. Nevertheless, the enzymes were not able to hydrolyze polyethylene terephthalate (PET). Furthermore, the three-dimensional models of these enzymes showed structural differences among them, mainly FvCut1, which presented a narrower opening cleft to access the catalytic site. Therefore, our study contributes to exploring the diversity of fungal cutinases and their potential biotechnological applications.

Characteristics of recombinant xylanase from camel rumen metagenome and its effects on wheat bran hydrolysis

In the present study, we explored the effects of a novel xylanase from camel rumen metagenome (CrXyn) on wheat bran hydrolysis. CrXyn was heterologously expressed in Escherichia coli and showed maximum activity at 40 °C and pH 7.0. Furthermore, CrXyn exhibited preferential hydrolysis of xylan, but no obvious activity toward other substrates, including carboxymethylcellulose and Avicel. Using wheat straw xylan as a substrate, the Km and Vmax values for CrXyn were 5.98 g/L and 179.9 μmol xylose/min/mg protein, respectively. Mn²⁺ was a strong accelerator and significantly enhanced CrXyn activity. However, CrXyn activity was inhibited (~50 %) by 1 mM and 5 mM ethylenediaminetetraacetic acid (EDTA) and completely inactivated by 5 mM Cu²⁺. CrXyn tolerated 5 mM sodium dodecyl sulphate (SDS) and 15 % methanol, ethanol, and dimethyl sulfoxide (DMSO), with >50 % residual activity. CrXyn effectively hydrolyzed wheat bran, with xylobiose and xylotetraose accounting for 79.1 % of total sugars produced. A remarkable synergistic effect was found between CrXyn and protease, leading to an obvious increase in amino acids released from wheat bran compared with the control. CrXyn also enhanced the in vitro hydrolysis of wheat bran. Thus, CrXyn exhibits great potential as a feed additive to improve the utilization of wheat bran in monogastric animal production.

Characterization of a New Xylanase Found in the Rumen Metagenome and Its Effects on the Hydrolysis of Wheat

Wheat is the main ingredient of poultry diet, but its xylan has an adverse impact on poultry production. A novel xylanase from beef cattle rumen metagenome (RuXyn) and its effect on the wheat hydrolysis were investigated in the present study. The RuXyn coded for 377 amino acids and exhibited low identity (<40%) to previously reported proteins. The RuXyn was heterologously expressed in Escherichia coli and showed maximum activity at pH 6.0 and 40 °C. The activity of RuXyn could be increased by 79.8 and 36.0% in the presence of Ca²⁺ and Tween 20, respectively. The soluble xylan and insoluble xylan in wheat could be effectively degraded by RuXyn and xylooligosaccharides produced accounting for more than 80% of the products. This study demonstrates that RuXyn has substantial potential to improve the application of wheat in poultry production by degrading wheat xylan and the accompanying xylooligosaccharides produced.