Diversity of mixed microorganism population after screening in the presence of selected VOCs

Abstract

Biological methods of productive gases treatment from Volatile Organic Compounds are based on the catalytic activities of degradative enzymes from environmental microorganisms. That is why screening for microorganisms able to degrade xenobiotics is performed. In order to isolate microorganisms able do degrade selected VOCs (vinyl acetate and styrene), soil sampling was performed in the area of Synthos S.A. in Oswiecim (Poland) (formerly Chemical Company “Dwory” S.A.) in August 2006. Two independent localizations were chosen for the collection of samples, and they were the outlet of gases arising during polymerisation of polyvinyl acetate and polystyrene. Different selection media were applied. They consisted of mineral salts solution, buffer components, and selective factor. As the selective factor increasing concentrations (50÷4000 mg/dm3) of vinyl acetate or constant concentration of styrene (100 mg/dm3) were applied. There was no increase of styrene concentration due to the significant drop in the amount of mixed population of microorganisms after application of that selective factor. Isolation, determination of microorganisms’ amount on the grounds of colony morphology and results of the Gram staining of cells, were carried out after introduction of vinyl acetate in the concentrations of 1500, 2000, 2500, 3000 and 3500 mg/dm3, and at the end of 6 weeks adaptation to styrene. Presence of selected VOCs caused significant changes in the amount and composition of mixed population of microorganisms. Both, vinyl acetate and styrene, resulted in the decrease of the initial number of populations. The ratio of Gram-negative to Gram-positive cells was changing in the presence of selected VOCs. In the beginning Gram-negative bacteria predominated. Increasing concentrations of vinyl acetate brought about gradual decrease in the number of Grampositive bacteria, and finally after application of 3000 mg/dm3 of vinyl acetate mixed populations consisted of only Gram-negative bacteria. Different chemical structure of styrene probably caused almost complete decay of Gramnegative bacteria in the presence of that selective factor. Differences in the structure of the bacterial cell envelopes are most likely the reason of increased survivability of Gram-positive bacteria, mainly filiform cells of Actinomycetes.