ISOLATION OF A BENZENE-TOLERANT BACTERIUM AND ITS HYDROCARBON DEGRADATION

After treatment of deep-sea sediment samples (collected from a depth of 1,945-m in Suruga Bay) with 20 v/v% benzene followed by 50 v/v% kerosene, fifty-six halotolerant bacteria were isolated as candidate hydrocarbon degraders that also possessed the characteristic of benzene-tolerance. One of the isolates showed halotolerant growth and tolerance to various kinds of organic solvents (OSs) such as 5 v/v% benzene, 10 v/v% toluene and 10 v/v% p-xylene. From these characteristics, in addition to its morphological and biochemical characteristics, it seemed to be a variant strain of Flavobacterium sp. and was tentatively named strain no. DS-711. The correlation between log p, used as a parameter for the degree of toxicity of the OSs, and growth on the OSs was further examined using the benzene-tolerant strain DS-711 and the toluene-tolerant Pseudomonas putida strain IH-2000. The results indicated that the mechanism of OS tolerance of DS-711 was different from that of P. putida strain IH-2000. Furthermore, a hydrocarbon degradation experiment indicated that the benzene-tolerant strain DS-711 had a greater n-alkane degrading ability compared to that of our selected control strains, the OS-sensitive Alteromonas sp. strain no. DS-201 and the toluene-tolerant P. putida strain IH-2000. With stepwise addition of concentrated cell suspension, strain DS-711 could degrade more than 90% of n-alkanes in kerosene.