Production of itaconic acid from sweet potato (Ipomoea batata) peel using naturally occurring fungi in solid state fermentation

Abstract

This study evaluates the potentials of sweet potato peel as a substrate for itaconic acid production in solid state fermentation using naturally occurring fungi. Sweet potato peel was analyzed for proximate composition using standard methods. Fungi were obtained from the peel by solid state fermentation and identified using microscopic and molecular methods. Fermentation for itaconic acid production was done using isolated fungus and Aspergillus niger (ATCC 16888) was used as control. Optimization of fermentation parameters was carried out using standard procedures. Assay for itaconic acid and total titratable acidity (TTA) were analyzed using standard methods. Reducing sugar was obtained using DNSA method. Proximate composition of the peel reveals carbohydrate content to be 79%, protein, 5% and ash, 4%. Fungus isolated was identified as Aspergillus flavus L-2482/2012. Highest itaconic acid production by A. flavus was 7.74±0.00 mg/ml on day 5 at 30 g substrate concentration. Using 2 ml of 1 x 107 spores/ml, A. flavus and A. niger produced 6.97±0.13 and 6.67±0.09 mg/ml respectively. Optimum temperature for itaconic acid production was 30°C for A. niger and A. flavus. TTA ranged between 0.04±0.00 to 0.21±0.01 and 0.05±0.00 to 0.26±0.00 mg/ml for A. niger and A. flavus respectively. The highest reducing sugar, 0.51±0.00 mg/ml was obtained at substrate concentration 40 mg/ml on day 5 by A. flavus while A. niger had reducing sugar value of 0.37±0.00 mg/ml. In conclusion, A. flavus L-2482/2012. has great potentials for itaconic acid production using sweet potato peel in solid state fermentation under optimized conditions.