Isolation And Analysis Of A Novel Isolate Serratia Sp.ZS6 Producing Biosurfactant And Lipase

With the rapid progress of social economy and scientific technology,demands for quality lifes are getting higher and higher.Currently,there are several ways of disposal for waste oils,such as physical,chemical,physicochemical and biological methods.Biological method refers to the degradation of oil by microorganisms through metabolic pathways,which is not only environmental friendly,but also produces biosurfactants,lipase and other byproducts with industrial application values.Through the modified T-RPLP(mT-RFLP)analysis,we isolated the ZS6 strain derived from petroleum sludge at Zhoushan coastal area.The strain is capable of assimilating olive oil and producing biosurfactant.We demonstrated that ZS6 belonged to Serratia sp.after overcoming the non-specificity of the university primer 27F for amplification of 16S rDNA in ZS6.The biosurfactant of ZS6 appeared to be a type of cyclolipopeptides by using acid hydrolysis and ninhydrin staining analyses.Emulsifying index against toluene E24 by the surfactant reached 100%.Agar plate immunoprecipitation showed that the surfactant was a non-ionic type,which resembled serrawettin produced by many Serratia spp.The CMC value of crude extract was 19.35 g/L,and the productivity of the crude extract was approximately 70 g/L.Serratia sp.ZS6 exhibited a high efficiency to degrade and assimilate olive oil with the consumption of 90%after 64 h cultivation.The lipase activity reached 58000 U/L when pNPB was used as a substrate.By using an in-gel lipase assay and NanoLC-ESI-MS/MS analysis,the lipase amino acid sequence and its coding DNA sequence in ZS6 was obtained.Sequence alignment analysis indicated that the lipase belonged to the lipolytic enzymes subfamily III of the family I.The optimal temperature and pH range of the ZS6 lipase was 40? and 7.0-8.0 respectively.Ca2+ and methanol could enhance its activity significantly.The lipase displayed the optimal activity at 12%(120g/L)salinity,3.4-fold higher than seawater salinity(3.5%).Together,we show that the isolated oil-degrading Serratia sp.ZS6 strain is able to secrete biosurfactant and lipase.This study lays a foundation for oily wastewater treatment and biodiesel production and is suitable for development of bioremediation methodologies.