Determination of optimal growth conditions for bacterial isolates adapted to long-term pollution

Biodegradation of oil and petroleum products is one of the most effective methods of ecosystem cleanup. Microorganisms adapted to long-term pollution are of particular interest, as they possess unique metabolic pathways and are adapted to stressful environmental conditions. Determining the optimal environmental parameters for the growth of microorganisms is one of the most important stages in the creation of highly effective biopreparations that are active even under extreme environmental conditions. The aim of this work was to isolate and characterize bacterial strains from oil sludge, detect optimal growth conditions, evaluate microbial ability to decompose benzoate as a model compound. Cultures were enriched in a 5-fold diluted lysogeny broth (LB) supplemented with 1% diesel fuel, followed by a mineral medium containing 250 mg/L benzoate as a growth substrate. Three bacteria, no. 8, 10, and 12, were isolated from the benzoate-supplemented culture medium. The growth ability of bacteria was tested in LB medium under different temperature, pH and NaCl concentration parameters. The ability to degrade benzoate was determined by the activity of key enzymes, catechol 1,2-dioxygenase (12CDO), catechol 2,3-dioxygenase (23CDO), protocatechuate 3,4-dioxygenase (34PCDO). All bacteria demonstrated vigorous growth across a wide range of temperatures, acidities, sodium chloride concentrations, and the ability to actively degrade sodium benzoate. The optimal growth temperature for all isolates was 30°C. Active growth was observed at pH 6.0-8.0. At various salt concentrations, the cultures grew vigorously from 0% to 7%, with active adaptation occurring at up to 3%. In cell-free extracts of bacteria grown with benzoate, the activity of 12CDO, 3,4-PCDO and 23CDO was detected. The study found that microbial cultures isolated from oil sludge were capable of vigorous growth across a wide range of temperatures, acidities, and salinities, demonstrating the ability of these strains to be used in extreme environmental conditions.