Optimization of Process Variables for the Production of Oxalic Acid from Sweet Potato Starch Hydrolyzate.

In this study optimization of oxalic acid production from Sweet Potato Starch Hydrolyzate (SPSH) using Aspergillus niger was investigated. The effects of three independent variables (concentrations of SPSH, fermentation time and pH) on the response (oxalic acid yield) and their reciprocal interactions were established using Response Surface Methodology (RSM). The box behnken design (BBD) was used to generate a total of 17 fermentation runs, which were subsequently conducted. A second-order mathematical model was obtained to predict the oxalic acid yield. A statistical model predicted the highest conversion yield of oxalic acid to be 103.274 g/l, at the optimal condition of SPSH of 149.97 g /l, time of 9 days, and pH of 6. The optimized condition was validated with the actual oxalic acid yield of 103.26 g/l. This work revealed that sweet potato starch could serve as alternative carbon source for oxalic acid production and the results could be scaled up to industrial production. Keywords: Sweet potato, Response Surface Methodology, Oxalic acid, Optimization, Aspergillus niger