Optimization of Pectinase Production from Bacillus subtilis PSE-8 Using Cassava Peels as Substrate in Submerged Fermentation through Response Surface Methodology (RSM)

Abstract

Pectinases are widely used in food processing, textile and other allied industries. Cassava peels generated from cassava processing outfits constitutes one of the major environmental pollutions in Nigeria and there is need to find alternative economic value of the waste instead of indiscriminately disposing them as currently done. This study reports the optimization of pectinase production from Bacillus subtilis PSE-8 using cassava peels as substrate in submerged fermentation through response surface methodology. The pectinase-producing bacterium was isolated from a dump site at a fruit market in Oyigbo, Rivers state. Pectinase production was screened on agar plate with pectin as sole carbon source and zone of clearance recorded. Optimization was performed using central composite design of RSM. Four independent variables (pH, temperature, incubation time, and cassava peel concentration) at five levels each were used in the design which generated a total of twenty-five runs. The responses monitored were pectinase production (U/mL) and biomass (mg/mL). The bacterial isolate was identified using cultural, biochemical, and molecular (16S rRNA gene) analyses. Out of 8 bacterial isolates screened for pectinase-producing potential, 5 isolates showed varying zone of inhibition. PSE-8 showed highest zone of inhibition of 9 mm when screened on Agar plate using pectin as sole carbon source. Data obtained from RSM indicated the highest pectinase production (117.5 U/mL) at pH 9, temperature 45oC, cassava peel concentration 3 % w/v and incubation time of 3 days. The pectinase-producing bacterium was identified as Bacillus subtilis PSE-8 based on 16S rRNA gene sequence analysis. This study demonstrated that inexpensive cassava peel can be used as carbon source to produce pectinase by Bacillus subtilis PSE-8. Thus, will help to reduce the environmental pollution posed by the usual indiscriminate disposal of the waste as well as encourage reduction in the cost of pectinase production. RSM technique effectively showed a positive interaction between the different factors studied. The pectinase produced by this bacterium could be applied in various food processing and other allied industries.