Assessment of pectinase production by Bacillus mojavensis I4 using an economical substrate and its potential application in oil sesame extraction

摘要

Carrot (Daucus carota) peels, local agricultural waste product, is rich in lignocellulolytic material, including pectin which can act as an inducer of pectinase production. Pectinolytic enzymes production by Bacillus mojavensis I4 was studied in liquid state fermentation using carrot peel as a substrate. Medium composition and culture conditions for the pectinase production by I4 were optimized using two statistical methods: Taguchi design was applied to find the key ingredients and conditions for the best yield of enzyme production and The Box-Behnken design was used to optimize the value of the four significant variables: carrot peels powder, NH4Cl, inoculum size and incubation time. The optimal conditions for higher production of pectinase were carrot peels powder 6.5 %, NH4Cl 0.3 %, inoculum level 3 % and cultivation time 32 h. Under these conditions, the pectinase experimental yield (64.8 U/ml) closely matched the yield predicted by the statistical model (63.55 U/ml) with R² = 0.963. The best pectinase activity was observed at the temperature of 60 °C and at pH 8.0. The enzyme retained more than 90 % of its activity after 24 h at pH ranging from 6.0 to 10.0. The enzyme preserved more than 85 % of its initial activity after 60 min of pre-incubation at 30–40 °C and more than 67 % at 50 °C. The extracellular juice of I4 was applied in the process of sesame seeds oil extraction. An improvement of 3 % on the oil yield was obtained. The findings demonstrated that the B. mojavensis I4 has a promising potential for future use in a wide range of industrial and biotechnological applications.