optimization of low-temperature lipase production conditions and study on enzymatic properties of aspergillus niger

In order to obtain the optimum fermentation medium and conditions for extracellular lipase production by aspergillus niger, the fermentation conditions of aspergillus niger were optimized by single factor and response surface design, the enzymatic properties of the crude enzyme were also studied. the results showed that the optimum fermentation medium was soluble starch 4%, (nh4)2so4 0.1%, k2hpo4 0.1%, mgso4·7h2o 0.05%, peptone 3%, olive oil 1.05%, initial ph 7. the optimal fermentation conditions were 30℃, the sample size was 26 ml/250 ml and the shaking speed was 213 r/min. the optimized lipase activity was 1.55 u/ml, which was 7.75 times of the pre-optimized lipase. it was found that when the ph value of lipase was 7.0, the activity of lipase reached its maximum value of 79.3±6.82%. when the ph value was between 6.0 and 8.0, the activity of lipase could be kept above 60% and the stability was good. at the same time, through the study of the temperature stability of lipase, found that the lipase was stable at 25℃- 35℃, its activity could reach more than 70%. when the enzyme activity reaches the maximum (107.6±9.57%), the temperature was 30℃.