Exploiting 1,3-Propanediol Production by a Clostridium beijerinckii Strain: The Role of Glycerol and Ammonium Sulfate Concentrations

In this study, we optimized the initial concentrations of glycerol and (NH4)2SO4 to enhance 1,3-propanediol (1,3-PDO) production by Clostridium beijerinckii strain Br21. A central composite rotational design (CCRD) was employed, varying glycerol concentrations between 158 and 441 mmol L−1, and (NH4)2SO4 concentrations between 4.4 and 25.8 mmol L−1. The CCRD identified optimal conditions at 441.42 mmol L−1 for glycerol and 25.8 mmol L−1 for (NH4)2SO4. The optimized medium resulted in a 112% increase in 1,3-PDO production compared to the original medium. Analysis of NH4+ and SO42− ions under optimal conditions revealed a higher consumption of NH4+ than SO42−. Furthermore, a quantitative gene expression analysis revealed that while the expression of genes responsible for glycerol uptake and ATP sulfurylase remained unchanged, the expression of the dhaM gene, which encodes the oxidative phosphoenolpyruvate:dihydroxyacetone phosphotransferase, increased approximately 6-fold. In the reductive pathway, the expression of the dhaB1 gene, encoding glycerol dehydratase, and the dhaT gene, encoding 1,3-propanediol dehydrogenase, increased 2.5- and 5-fold, respectively. The upregulation of these genes supports the hypothesis that the optimal concentrations of glycerol and (NH4)2SO4 enhance the 1,3-PDO production by C. beijerinckii Br21.