Expression And Identification Of Lac In Pichia Pastoris And Optimization Of Fermentation Process

β-D-galactoside galactohydrolase (EC 3.2.1.23)is usually named as lactase. It is mainly used to produce dairy products which contain low lactose and relieve lactose malabsorption. Also lactase can be used for treatment of"lactase intolerance". But at present the yields of lactase products are generally low , and price and cost are very high. so it has not been used widely. However the genetic engineering technology effectively promotes the development of lacase.In this paper, a lactase eukaryotic expression vector was successfully constructed and expressed in pichia pastoris. All kinds of fermentation conditions of lactose were explored. After-treatment of fermentation mash has been done. The experimental results indicated that the optimal pH of lactase fermentation was 5.2,the best temperature was 30℃, the final Fed-Batch of methanol was controlled in the range of 1.6-3.3, dissolved oxygen value was controlled at 20%-40%. The results showed that the activity of lactase was 7800U/ml. The fermentation mash adopted ultrafiltration membrane with molecular weight of 20kD to condense .Thus it can not only reduce the loss of proteins , but also eliminate redundant impurity .