Study On Resuscitation-promoting Factor Strengthened Mechanism Of Bioremediation In Polychlorinated Biphenyls Contaminated Soil

Polychlorinated biphenyls(PCBs)are typically persistent organic pollutants in the soil environment,posing a threat to the ecological environment and human health.The bioremediation technology of PCBs contaminated soil has the characteristics of environmentally friendly and low cost,but low remediation efficiency seriously limits its practical application.The PCBs-degrading bacterium that is in the VBNC state may be a significant factor influencing their efficiency,and some VBNC bacteria can be resuscitated by resuscitation-promoting factor(Rpf).In this paper,the Rpf of Micrococcus luteus and Rhodococcus biphenylivoran TG9 were used as research objects to study the effect of Rpf.At the same time,the mechanism of Rpf accelerating biodegradation of PCBs contaminated soil was studied.The main findings as follows:(1)Rpf promoted the growth of TG9,and increased the degradation rate of BP/PCBs.The lag phase of TG9 was shortened by culture supernatant from Micrococcus luteus(SRpf),the purification containing Rpf(PRpf)and the lysate of E.xoli containing Rpf(LRpf).The BP degradation rates at 60 h were 73.0%,63.8%and 76.7%respectively at the initial concentration of BP is 5000 mg/L,which were significantly higher than that of the control group(P<0.05);and the PCBs degradation rates at 60 h were 40.8%,52.0%and 60.0%respectively,at the initial concentration of PCBs is 70 mg/L,which were significantly higher than that of the control group(P<0.05).It was particularly noteworthy that LRpf worked best.(2)After TG9 was induced into VBNC state by low temperature and oligotrophic conditions,its cell morphology and enzyme activity were changed.The cell morphology of VBNC state TG9 changed from short rod to globular,and the cell size became smaller,the cytoplasm was concentrated and the cell wall thickness increases.Some enzyme activity of VBNC state TG9 cells reduced,such as esterase(C4),esterase lipase(C8),leucine arylamidase,valine arylamidase,naphthol-AS-BI-phosphohydrolase,α-glucosidase and β-glucosidase,however,enzyme activities of alkaline phosphatase,acid phosphatase,and lipid esterase(C8)were enhanced.(3)Rpf had a resuscitation effect on TG9 in VBNC status.The VBNC state TG9 resumed growth after adding LRpf for 36 h.The BP/PCBs degradation rate at 60 h were 29.3%and 24.3%respectively,which were significantly higher than that of the control group(P<0.05).(4)Rpf could accelerate the biodegradation of PCBs in the soil.The PCBs degradation rate at 49d was 35.8%by the addition of LRpf and TG9 to PCBs contaminated soil,which was significantly higher than that of the control group(P<0.05).The soil PCBs degradation rate at 49d was 34.2%by the addition of LRpf and TG9 induced by low temperature and oligotrophic for 90 days to PCBs contaminated soil,which was significantly higher than that of the control group(P<0.05).(5)Rpf could increased the number of the culturable bacteriu.Rpf affected the microbial population abundance and species diversity in soil,and could stimulate the resuscitation of Rhodococcus genus and Stenotrophomonas genus in soil.The results of this paper will help to further reveal the mechanism of action of Rpf on functional bacteria in the VBNC state,and provide a theoretical basis for the application of Rpf in remediation of soil organic contaminants.