Response surface optimization of process parameters for the production of microbial biomass and single cell protein from Aspergillus niger using banana peel as substrate

Abstract

Response surface methodology (RSM)-based central composite rotatable design (CCRD) on four variables viz. temperature (20-40oC), pH (4-8), substrate concentration (5-25 %), and fermentation period (1-5 days) were employed for optimizing the production of biomass and protein from Aspergillus niger using banana fruit peel. The experimental results were significantly (P<0.05) fitted into second-order polynomial models to describe and predict the response quality in terms of the biomass and protein with R2 of 0.9669 and 0.9521, respectively. The linear, quadratic and interactions effects of the four variables on the yield of biomass and protein were investigated. It was found that the effects of process variables on production of biomass and protein were significant (P<0.05) and the strongest effect was given by the fermentation period. After numerical optimization, the predicted optimum conditions were obtained as temperature of 34.27oC, pH of 6.32, substrate concentration of 10% and fermentation period of 4 days which were verified through confirmatory experiments. Under these optimal conditions, the experimental values (biomass: 18.56 ± 0.16 g/L and protein: 59.06 ± 0.13 %) agreed well with the predicted values (biomass: 18.1105 g/L and protein: 58.7177 %) indicating the suitability of developed models within the acceptable range of the responses.