Investigation of low-temperature lipase production and enzymatic properties of Aspergillus Niger

To obtain the optimum fermentation medium and circumstances for extracellular lipase construction (as an important biocatalyst and promising industrial enzyme) 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 studied. The results displayed 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% and 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 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 temperature stability of lipase, found that the lipase was stable at 25℃- 35℃, its activity could reach more than 70%. When activity of enzyme reaches to maximum 107.6±9.57%, the temperature was 30℃.