Production of Itaconic Acid by Aspergillus terreus from Sorghum Bran Hydrolysates and Optimization for Fermentative Production

Abstract

Itaconic acid is a versatile renewable industrial chemical, but its widespread use is limited by high production costs relative to petroleumbased alternatives such as acrylic acid. Dilute acid hydrolysates of red bran and white bran were produced from waste brans of red and white sorghum, respectively, and their suitability for itaconic acid production by Aspergillus terreus was investigated. Forty-six A. terreus isolates were screened on a defined medium, and the highest itaconic acid producers were employed in batch fermentation of the hydrolysates. Up to 7.8 g/L and 5.2 g/L itaconic acid (22.9% and 15.1% of stoichiometric yield) were obtained from red bran dilute acid hydrolysate and white bran dilute acid hydrolysate, respectively. The titres were lower than were obtained from a defined glucose medium where up to 64 g/L (78% of the theoretical yield) was produced. Several conditioning processes were then employed. Activated charcoal treatment was the best hydrolysate treatment method, with the removal of 42% of phenolic compounds and 38% of condensed tannins. It also resulted in a significant rise to 9.2 g/L itaconic acid (24.6% of the % theoretical yield possible). This is the first report of itaconic acid production from sorghum bran and provides a route to valorizing this waste.