Development Of A Mixed Microbial-Agent Efficiently Degradating High-Molecular-Weight-Poly Cyclic-Aromatic-Hydrocarbons

This research investigated the biodegradation of high molecular weight polycyclicaromatic hydrocarbons (HMW PAHs) in liquid medium and soil by bacteria (Mycobaceriumsp. SH141, Acinetobacter sp. SH142and Microbacterium sp. SH132) that were isolatedfrom polycyclic aromatic hydrocarbons contaminated soils. The bacteria could use pyreneand Benzo[a]Pyrene (B[a]p) as sole carbon and energy source in a basal salts medium (BSM)and mineralized significant amounts of B[a]p and pyrene. A mixed solid microbial agentwere developed by axenic cultures of three isolates described above in LB medium toabsorption carrier. Further, the biodegradation of mixed solid microbial agent forHMW PAHs were studied in contaminated soil. In order to identify the bacterial speciesinvolved in hydrocarbon degradation, we used microcosms containing pyrene and B[a]PBSM and HMW PAHs contaminated soil, analysis of the16S rRNA gene sequences withdenaturing gradient gel electrophoresis (DGGE) and sequencing.The results show that:①After10days, the degradation rate of200mg/l concentrationpyrene by Mycobacerium sp. SH141, Acinetobacter sp. SH142and Microbacterium sp.SH132were77.1%,18.1%and13.2%in BSM, respectively;②The degradation rate of10mg/l concentration B[a]P in BSM by Mycobacerium sp. SH141was47.3%after60days.Conversely, Acinetobacter sp. SH142and Microbacterium sp. SH132exhibited growthrates but weak utilization to B[a]P by each single strain;③We found that mixed inocula ofMycobacerium sp. SH141, Acinetobacter sp. SH142and Microbacterium sp. SH132,degraded200ppm concentration pyrene and10ppm concentration B[a]P in co culture. After10days and60days, degradation rates of pyrene and B[a]P were93.2%and67.5%,22.1and19.8percentage point higher than that of single Mycobacerium sp. SH141in BSM,respectively.④Results of counting for Acinetobacter sp. SH142and Microbacterium sp. SH132and results of RT PCR for Mycobacerium sp. SH141in absoption tests on differentcarriers show that vermiculite is more appropriate as microbial agent carrier than activatedcarbon, shell powder, wood chips and diatomite.⑤After108days of treatment,degradation rate of PAHs in soil with5%of mixed microbial agent was13.6percentagepoints higher than that of control kit. The results indicate that microbial agent cansignificantly enhance the biodegradation of PAH in contaminated soil, especiallyHMW PAHs with more than four aromatic rings. Results show that the microbial agent hasstrong potential of application in bioremediation of PAHs comtaminated soil...