Optimization of succinic acid production from xylose mother liquor (XML) by Actinobacillus succinogenes using response surface methodology

In the present study, conditions for succinic acid (SA) production using xylose mother liquor (XML) as culture medium by Actinobacillus succinogenes GXAS137 were optimized. Firstly, single-factor experiments were performed to evaluate the basal culture medium for SA fermentation. Thereafter, the Plackett-Burman design was used to screen out three significant factors of XML, corn steep liquor powder (CSLP) and MgCO3 affecting the SA yields from the original nine factors. Subsequent use of steepest ascent experiment determined the center area of the three factors. Finally, the response surface methodology was used to further optimize the interactions between the three main factors and predict the maximum SA concentration through Box-Behnken design. The optimal conditions of SA fermentation were maximally documented in the XML (110 g/L), CSLP (18.86 g/L) and MgCO3 (69.12 g/L). The maximum production of SA was 58.06 +/- 0.57 g/L after 60 h with a yield of 0.72 +/- 0.06 g/g total sugar, approaching the predicted value (57.99 g/L). It was 1.63-fold of the SA production obtained with the basic medium (35.54 g/L). In addition, batch fermentations were carried out in a 1.3-L stirred bioreactor and SA reached 58.47 g/L. These results indicate that XML could be an alternative substrate for the economical production of SA by A. succinogenes GXAS137.