Effects of Cultivation Temperature and Type of Organic Acid Addition on Anaerobic Benzene-Degrading Enrichment Culture under Methanogenic Condition

In this study, we investigated the effects of organic acid addition and cultivation temperature on anaerobic methanogenic benzene-degrading enrichment culture which include Syntrophobacterales bacterium Hasda-A, a putative benzene degrader, and its relatives. Benzoate, crotonate, fumarate and acetate, added respectively with benzene, retarded benzene degradation in all cases. However, it was implied that the addition of these organic acids may maintain the number of cells of Hasda-A and its relatives. Cultivation temperature was varied at 3°C intervals ranging from 25°C, at which we have succeeded in obtaining an anaerobic benzene degrading culture, to 37°C, the optimum cultivation temperature for mesophilic methanogens. It was shown that cultivation at 31°C or below can maintain benzene degradation rates higher than that at 34°C and above. In all the experiments, the number of 16S rRNA gene copy of Hasda-A and its relatives correlated with benzene degradation.