Characterization of diesel-degrading, hydrolytic enzymes-producing Streptomyces spp. isolated from fuel-oil polluted soils

Abstract

Thirty-four different soil Streptomyces isolates previously recovered from soils of different gas stations that were historically polluted with fuel oil for long time were analyzed for their ability to produce five different hydrolytic enzymes, as well as for their potential to use diesel fuel as a sole carbon source for growth, in addition to the PCR amplification of the alkane hydroxylase gene (alkB). Results showed that 97.68% were producing at least one of the five hydrolytic enzymes, pectinase, carboxymethyl cellulase (CMCase), lipase, chitinase or amylase. Three isolates (1a, 5e, and 12a) were only producing all the tested enzymes and were able to use diesel fuel as a sole carbon source for growth as assessed by biochemical enzymatic assay and dry weight measurements. The capability of these isolates to use diesel as a sole carbon source for growth was obvious by changing the colourcolour of the reaction mixture within 6 hours, and the increase in dry weight after incubation for 28 days. Although the three isolates showed diesel degrading capability, they tested negative for harbouring the alkB gene by the PCR assay. alkB gene might not be the only gene responsible for alkanes degradation, and the isolates that grew on diesel and showed no PCR product might devoid the alkB gene.