Isolation and Degradation Characteristics of a HMW PAHs-Degrading Strain LD29

Two-liquid-phase(silicone oil-water) culture enrichment systems,with anthracene as carbon source,was used to enrichment PAHs-degrading strains from contaminated soil by crude oil.One strain,which can degrade phenanthrene,anthracene,fluoranthene,pyrene and benzo[a]pyrene,was isolated and identified as Sphingobium yanoikuyae based on 16S rDNA sequences,phenotypic characteristics and physio-biochemistry characteristics,and numbered as LD29.Degradation characteristics of LD29 in mineral salts medium(MSM) was measured by HPLC.After 4 days of growing in MSM with single PAH as carbon source,LD29 degraded phenanthrene,anthracene,fluoranthene,pyrene(initial concentration: 50 mg/L) by 92%,87%,28% and 7% respectively,but no benzo[a]pyrene was degraded.Anthracene enhanced the degradation of fluoranthene/pyrene by LD29,whereas fluoranthene/pyrene impeded anthracene degradation by LD29.MSM with high initial pH value(pH=9) favored the degradation of PAHs mixture in MSM by LD29.The degradation activity of LD29 can be improved by additional nutrition.Additional carbon source(glucose,200 mg/L) or nitrogen source(peptone,50 mg/L) accelerated fluoranthene(100 mg/L) degradation in MSM,with degradation rate 69%,81% respectively(CK: 34%) within 6 days.LD29 started to significantly degrade HMW PAHs from the 4th day in MSM with 5 PAHs(phenanthrene,anthracene,fluoranthene,pyrene and benzo[a]pyrene),and the degradation rate of pyrene and fluoranthene at day 6 were 44% and 58% higher than those of day 4 respectively,and the degradation rate of benzo[a]pyrene also reached to 17% at day 6.LD29 has significant potential for PAHs degradation,including high molecular weight(HMW) PAHs.