Genomic and functional insights into the thermophilic strain Geobacillus sp. Geo 8.1: a source of thermostable xylanase for sustainable bioprocesses

A thermophilic bacterium, designated Geobacillus sp. Geo 8.1, was isolated from a submarine hydrothermal spring of Ischia Island (Italy) and characterized through genomic and biochemical analyses to evaluate its biotechnological potential. The draft genome (3.41 Mbp; GC 52.5%) revealed 3,751 coding sequences, including complete pathways for carbohydrate, lipid, and protein metabolism, and enzymes involved in stress response and hydrocarbon degradation. Phylogenomic and digital DNA–DNA hybridization analyses placed Geo 8.1 within the Geobacillus thermoleovorans/Geobacillus kaustophilus cluster. Functional annotation highlighted diverse genes encoding thermostable hydrolases such as xylanases, β-xylosidases, lipases, proteases, and α-amylases, together with catalases and dehalogenases relevant to environmental and industrial applications. Crude enzyme extracts exhibited strong xylanase activity (184 U/mL at 65 °C), and thin-layer chromatography confirmed the production of xylose as the major hydrolysis product, indicating the coordinated action of endo-xylanase and β-xylosidase. Genome reconstruction further demonstrated a complete D-xylose utilization pathway linking hemicellulose degradation to central carbon metabolism. The combined genomic and enzyme data reveal Geobacillus sp. Geo 8.1 represents a promising thermophilic biocatalyst for producing thermostable enzymes applicable to lignocellulose valorization, bioremediation, and various industrial processes.