Xylanases are crucial enzymes for the bioconversion of lignocellulosic biomass. Despite extensive studies on microbial xylanase producers, the identification of new indigenous strains with enhanced enzyme activity remains a significant challenge. While there is some existing research on the isolation of xylanase-producing bacteria from Iran, our study specifically aimed to comprehensively isolate and characterize novel xylanase-producing bacterial strains from a diverse range of samples collected across the region. A total of 26 samples were collected from various regions of Iran. From these, 18 distinct bacterial isolates were obtained based on colony morphology. Among these, 13 isolates showed clear zones of xylan hydrolysis in the qualitative screening, indicating xylanase activity. Among these isolates S3 and S4 exhibited superior enzyme production. Strain S3 showed the highest activity of 11.56 U/mL at pH 9 and 40 °C, while S4 achieved 9.35 U/mL at pH 9 and 50 °C. Notably, S3 maintained significant activity across a broad pH range (pH 4–9), highlighting its adaptability. Molecular and phylogenetic analyses revealed these isolates to be previously uncharacterized, xylanase-producing variants of Bacillus spizizenii originating from Iran. Whole-genome sequencing of S3 revealed unique xylanase genes from the GH11 and GH43 families. Molecular docking indicated favorable substrate-binding affinities with the xynA1 (GH11) gene showing the strongest interaction with xylan (-9.4 kcal/mol), supported by kinetic parametersThese findings present new B. spizizenii strains as promising candidates for industrial applications, particularly where broad pH adaptability is required, and provide a genetic foundation for future enzyme engineering.
Bigdeli et al. (Fri,) studied this question.