Valorization of Wheat Straw Hydrolysate into Succinic Acid by Fermentation with Actinobacillus succinogenes

Succinic acid (SA) production from agro-industrial waste, such as lignocellulosic biomass, has been gaining interest. Traditionally, it is synthesized from petrochemical sources, a process associated with negative environmental impacts. In recent decades, efforts to develop cleaner production methods have led to the establishment of biotechnological routes based on fermentative microorganisms, such as Actinobacillus succinogenes. This strain is well known for its ability to metabolize a wide range of sugars, particularly glucose and xylose, which can be derived from the pretreatment of lignocellulosic biomass. However, due to the variable composition of the starting material, such as differences in fermentable sugar concentrations and the presence of inhibitory compounds, optimization of the fermentation process is necessary. In this study, the fermentation for production of bio-succunic acid from wheat straw hydrolysate was optimized in respect to medium composition. Two different dilutions of hydrolyzed wheat straw (50% and 90% v/v) were tested. In addition, the concentration of yeast extract, used as nutrients as supplement, and magnesium carbonate supplied for pH buffer, were evaluated at two levels: 10 and 25 g·L-1 for yeast extract, and 30 and 60 g·L-1 for magnesium carbonate. Various combinations of these compounds were investigated. The highest SA production (12.87 g·L-1, yield of 62.1%) was achieved using 90% (v/v) hydrolysate combined with 10 g·L-1 yeast extract and 60 g·L-1 magnesium carbonate. The results provide valuable insights into the utilization of challenging lignocellulosic substrates, such as wheat straw, for SA production and lay the groundwork for future process scale-up.