Application of Doehlert designs for water activity, pH, and fermentation time optimization for Aspergillus niger pectinolytic activities production in solid-state and submerged fermentation

摘要

The Doehlert design was applied to optimize water activity, pH, and fermentation time conditions for Aspergillus niger 148 pectinolytic activities production in solid-state (SSF) and submerged (SmF) fermentation. The fermentation technique had a great influence on the composition of pectinases produced by the fungus. Production of polygalacturonase was 5-fold higher in SmF than in SSF. However, pectin lyase production was 3 times higher in SSF than in SmF. Pectinesterase was only a 30% higher in SSF than in SmF. Optimization of the process was based on minimum pectinesterase production and maximal pectin lyase production. The optimal conditions to obtain the aforecited composition by a SSF process were initial pH 6.5-7, initial a_w 0.93-0.94, and 2 days of fermentation. For the SmF process they were initial pH 5.5-6.2, initial a_w above 0.99, and 3 days of fermentation. The results suggest that A. niger 148 overproduces pectin lyase under the optimized SSF culture conditions, as the concentration in the fermentation extract was around 0.25 g/l, representing approximately equals 65% of total extracellular proteins produced by the fungus.