Taxonomic and Enzymatic Characterization of Flocculibacter collagenilyticus gen. nov., sp. nov., a Novel Gammaproteobacterium With High Collagenase Production

Gilvimarinus xylanilyticus sp. nov., a novel 1,3-xylanase-secreting bacterium isolated from a marine green alga

1,3-xylan, an important organic carbon in the ocean, is peculiar to marine algae. 1,3-xylanase-secreting bacteria and their extracellular 1,3-xylanases play pivotal roles in the degradation and biomass conversion of 1,3-xylan. However, only a few 1,3-xylanase-secreting bacteria and 1,3-xylanases have been reported. Here, we identified a novel marine bacterium capable of secreting 1,3-xylanases, designated as strain HB14^T. Phylogenetic analysis revealed that strain HB14^T clustered tightly with known species of the genus Gilvimarinus, showing the highest 16S rRNA gene sequence similarity (97.7%) with the type strain of Gilvimarinus chinensis. Based on phylogenetic, genomic, chemotaxonomic and phenotypic studies, strain HB14^T was classified as a representative of a novel species in the genus Gilvimarinus, for which the name Gilvimarinus xylanilyticus sp. nov. was proposed. The type strain is HB14^T (=CCTCC AB 2022109^T = KCTC 92379^T). Four 1,3-xylanases secreted by strain HB14^T were identified based on genome and secretome analyses, and the two (Xyn65 and Xyn80) with relatively higher abundance in secretome were successfully expressed in Escherichia coli and biochemically characterized. They showed the highest activity at pH 6.0–7.0 and 40°C and released mainly 1,3-xylobiose and 1,3-xylotriose from 1,3-xylan. These data suggest that strain HB14^T acts as a player in marine 1,3-xylan degradation and recycling and that its extracellular 1,3-xylanases may have a good potential in 1,3-xylooligosaccharides preparation.

Optimized Recombinant Expression and Characterization of Collagenase in Bacillus subtilis WB600

Background: The collagenase encoding gene col was cloned into a pP43NMK vector and amplified in Escherichia coli JM109 cells. The shuttle vector pP43NMK was used to sub-clone the col gene to obtain the vector pP43NMK-col for the expression of collagenase in Bacillus subtilis WB600. The enzyme was characterized and the composition of the expression medium and culture conditions were optimized. Methods: The expressed recombinant enzyme was purified by ammonium sulfate, ultrafiltration, and through a nickel column. The purified collagenase had an activity of 9405.54 U/mg. Results: The recombinant enzyme exhibited optimal activity at pH 9.0 and 50 °C. Catalytic efficiency of the recombinant collagenase was inhibited by Fe3+ and Cu2+, but stimulated by Co2+, Ca2+, Zn2+, and Mg2+. The optimal conditions for its growth were at pH 7.0 and 35 °C, using 15 g/L of fructose and 36 g/L of yeast powder and peptone mixture (2:1) at 260 rpm with 11% inoculation. The maximal extracellular activity of the recombinant collagenase reached 2746.7 U/mL after optimization of culture conditions, which was 2.4-fold higher than that before optimization. Conclusions: This study is a first attempt to recombinantly express collagenase in B. subtilis WB600 and optimize its expression conditions, its production conditions, and possible scale-up.

A Novel Gelatinase from Marine Flocculibacter collagenilyticus SM1988: Characterization and Potential Application in Collagen Oligopeptide-Rich Hydrolysate Preparation

Although the S8 family in the MEROPS database contains many peptidases, only a few S8 peptidases have been applied in the preparation of bioactive oligopeptides. Bovine bone collagen is a good source for preparing collagen oligopeptides, but has been so far rarely applied in collagen peptide preparation. Here, we characterized a novel S8 gelatinase, Aa2_1884, from marine bacterium Flocculibacter collagenilyticus SM1988^T, and evaluated its potential application in the preparation of collagen oligopeptides from bovine bone collagen. Aa2_1884 is a multimodular S8 peptidase with a distinct domain architecture from other reported peptidases. The recombinant Aa2_1884 over-expressed in Escherichia coli showed high activity toward gelatin and denatured collagens, but no activity toward natural collagens, indicating that Aa2_1884 is a gelatinase. To evaluate the potential of Aa2_1884 in the preparation of collagen oligopeptides from bovine bone collagen, three enzymatic hydrolysis parameters, hydrolysis temperature, hydrolysis time and enzyme-substrate ratio (E/S), were optimized by single factor experiments, and the optimal hydrolysis conditions were determined to be reaction at 60 ℃ for 3 h with an E/S of 400 U/g. Under these conditions, the hydrolysis efficiency of bovine bone collagen by Aa2_1884 reached 95.3%. The resultant hydrolysate contained 97.8% peptides, in which peptides with a molecular weight lower than 1000 Da and 500 Da accounted for 55.1% and 39.5%, respectively, indicating that the hydrolysate was rich in oligopeptides. These results indicate that Aa2_1884 likely has a promising potential application in the preparation of collagen oligopeptide-rich hydrolysate from bovine bone collagen, which may provide a feasible way for the high-value utilization of bovine bone collagen.