Functional microbial diversity in arid soils of Uzbekistan: discovery of a biotechnologically valuable Bacillus amyloliquefaciens strain

In this study, we assessed the functional microbial diversity of arid and anthropogenically impacted soils of Uzbekistan to identify bacterial strains with biotechnologically important enzymatic activities. A total of 20 Bacillus isolates obtained from oil-sludge–contaminated areas and intensively irrigated agricultural fields were screened for their ability to produce proteases with milk-clotting activity (MCA). Preliminary screening on skim-milk agar revealed three isolates exhibiting strong proteolytic activity (hydrolysis zones > 20 mm). Quantitative assays performed in a lactose-based fermentation medium identified isolate 6/4/2 as the most active strain. MALDI-TOF mass spectrometry and 16S rRNA gene sequencing confirmed this isolate as Bacillus amyloliquefaciens UzRSMMT-413. Under optimal cultivation conditions (35–40 °C; pH 7.5), UzRSMMT-413 reached a maximum MCA of 400 U mL⁻¹ after 48–72 h and demonstrated an MCA/protease activity ratio of 5.18, indicating high specificity toward casein with minimal nonspecific proteolysis. These findings highlight the arid soils of Uzbekistan as an ecologically rich yet understudied reservoir of microbial resources with significant biotechnological potential. The functional diversity identified in these soils offers promising enzymatic candidates for cheese making, fermented dairy production, and other low-energy bioprocesses. Overall, the study underscores the conservation value and applied importance of microbial biodiversity within the semi-natural landscapes of the Palearctic–Oriental transition zone.