Genomic Functional Analysis and Cellulase Characterization for the Enzyme-Producing Strain Bacillus subtilis Y4X3 Isolated from Saline–Alkaline Soil in Xinjiang, China

Biotechnological research and application of microbial enzyme production have consistently been focal points for scientific inquiry and industrial advancement. In this study, <i>Bacillus subtilis</i> Y4X3 was isolated from saline-alkaline soil in Xinjiang, China. Extracellular enzyme production analysis revealed that <i>B. subtilis</i> Y4X3 can secrete various enzymes, including cellulase, xylanase, protease, and amylase. Sequencing and assembly of the complete genome of this strain revealed a genome size of 4,215,636 bp with 43.51% C + G content, including 4438 coding genes. Genome annotation was performed with databases to predict gene functions in <i>B. subtilis</i> Y4X3, and a variety of genes related to carbohydrate metabolism were identified. A cellulase-encoding gene was subsequently cloned from the genome and heterologously expressed in <i>Escherichia coli</i>. The optimum pH and temperature for the purified cellulase Cel5A were 5.0 and 60 °C, respectively. Stability analysis revealed that Cel5A remained stable at pH 5.0-9.0 and 20-60 °C; after 1 h at pH 9.0, the relative enzyme activity still exceeded 60%. Additionally, Cel5A was positively affected by various metal ions and exhibited good tolerance to multiple chemical reagents. The results indicate that <i>B. subtilis</i> Y4X3 has the potential to produce a variety of industrial enzymes and could serve as a promising candidate for more efficient and cost-effective industrial applications; the characterized thermostable and alkali-resistant cellulase Cel5A also has potential applications in biotechnology and industry.