Isolation and medium optimization of high lipase producing strain

In this study,high-yielding lipase strains were isolated and screened from food and oil contaminated soils,and fermentation conditions were optimized for maximal enzyme production.320 lipase-producing strains of bacteria,yeasts and molds were obtained through 35 rich in oil samples,in which bacteria X-13 produced the highest enzyme activity,about 3.5U/ml.The optimal carbon source for bacteria X-13 fermenting and producing lipase was soluble starch,and the optimal nitrogen source was beef extract,and Mg2+,Ca2+,Co2+were found to stimulate the lipase activity,however,Fe2+,Mn2+,Cu2+inhibited the lipase yield of the strain X-13.The modified complex medium by orthogonal experiment design were that soluble starch6g/L,beef extract 4g/L,yeast extract 0.5g/L,MgSO4·7H2O 0.2g/L,polyethylene glycol(PEG400) 0.6 ml/L,K2HPO41g/L,olive oil emulsion 20ml/L,pH 7.0.Under the optimized culture conditions,the lipase activity of X-13 was 9.28U/ml and improved by 2.65 folds compared with the initial screened media after 72h of shaking incubation at 30℃.