Biofuels & Bioenergy

Itaconic acid (IA) is a unique di-carboxylic acid widely used as a platform chemical to produce several value-added industrial products. It is currently produced industrially by the fermentation of glucose-based sugar solutions using Aspergillus terreus which compete with potential food applications and this in turn limits its industrial applications. This work replaces commercial glucose with glucose from a relatively underutilised feedstock, sorghum bran the residue of the starch extraction process, for the production of IA to decrease its production cost. Compositional analyses of brans from the white and red sorghum varieties did not reveal significant differences in most parameters. The starch content was high in both brans, with white bran having 52.96% and Red bran having 67.26% starch content. They also contained fairly considerable amounts of minerals (1.4% and 1.7% respectively) and protein (19.2% and 21.4% respectively). The brans were saccharified enzymatically and using various chemicals and the hydrolysates obtained from the most efficient conditions were tested for their ability to support A. terreus growth using a phenotypic microarray process. The hydrolysates were then utilised in shake flask fermentations to produce IA. No inhibitory effect on A. terreus growth in the dilute acid hydrolysates while production was limited relative to glucose controls. The effects of various factors including phosphates, sulphates, sorghum tannins and buffer type as potential inhibitors of IA production were investigated. A yield of around 10g/L IA was produced from the enzymatic hydrolysate.