Optimization of fermentation conditions as a metabolic strategy for the high-yield and high-selectivity bio-based 2,3-butanediol production

Abstract

Optimization of culture conditions can be used as an alternative metabolic control strategy to genetic engineering to improve bio-based 2,3-butanediol (2,3-BDO) production, especially its yield and optical purity. In this study, a first-order model was determined to predict the 2,3-BDO yield, which reached about 90% in batch cultures at 32° C, pH = 5, and kLa ∼ 5.0 ± 2.7 h−1, using a new and safe Paenibacillus peoriae NRRL BD-62. No acetoin accumulation and an absolute levo-2,3-BDO optical purity were also verified. About 39.4 g/L of 2,3-BDO, with a yield of 0.43 g/g, and a levo-:meso-2,3-BDO ratio of 1.9:1, was obtained at the expense of acetoin, lactic acid, and ethanol in fed-batch fermentation at kLa adjusted within its optimized range (∼7.5 h−1) to overcome operational limitations using high initial glucose concentrations. The low pH contributed to the carbon flux shift toward the levo-isomer synthesis, possibly due to the preferential butanediol dehydrogenase activation, while the highly oxygen-limited environment favored the complete acetoin conversion, enhancing the 2,3-BDO yield. These results provide significant contributions to the high-yield, acetoin-free, and safe bio-based 2,3-BDO production of particular interest in large-scale fermentations.