Studies On Screening Of A Lipase-producing Microorganism From Oily Wastewater And Its Phenotype Characterization

Lipases are a special class of lipid hydro lases, widely used in oil, food, medicine, daily chemical industry etc. With the increasing improvement of people’s living standard and food industry, more and more oil is discharged into the water. The stability of lipase is poor, the production cost is very high, and lipase is very difficult to purify. In order to improve the application of lipase in the industrial field, the microbial screening with high lipase catalytic activity and stability will become the focus of lipase research. In this experiment one strain producing lipase was screened from waste water, and researched the lipase activity and degradation characteristics of the strain.Firstly, strains were screened from waste water, and lipase producing strains were screened by tween-80 medium and neutral red medium. The strain was identified by the physiological and biochemical characterization and 16S rDNA analysis. Secondly, growth curve of the strain was measured. In order to determine the optimal process parameters, the fermentation medium was optimized by response surface methodology, and oil degradation rate was optimized by orthogonal experimental design.The results show:Nine strains were screened from waste water. Through screening by selective medium and lipase activity determination, we obtained the strain X-l was the best for lipase producing strain. Its activity can be reached 8.635U/mL. Trough the physiological and biochemical characterization and 16S rDNA identification, the strain was belong to Klebsiella. It was named as Klebsiella sp. X-1. Trough studying the growth of X-1 strain, the best time of cultivation was determined is 16h. Through the response surface optimization of medium experiment, the best parameters of medium was obtained as follows:yeast extract fermentation 0.60%, soybean powder 2.00%, NaC1 0.95% and the lipase activity was 14.895U/mL. Through the orthogonal optimization of degradation rate experiment, the best parameters of degradation rate was obtained as follows:pH 7, rotation speed 140r/min, temperature 30℃. The degradation rate was 68.2%.