Effect of process parameters on 3-hydroxypropionic acid production from glycerol using a recombinant Escherichia coli

The top-valued platform chemical, 3-hydroxypropionic acid (3-HP), has a wide range of industrial applications but its biological production is not well established. Previously, the production of 3-HP from glycerol was demonstrated using a recombinant Escherichia coli strain expressing glycerol dehydratase (dhaB) and aldehyde dehydrogenase (aldH). The present investigation focuses on the effect of the culture conditions on the production of 3-HP from glycerol. The physicochemical parameters, such as pH, IPTG concentration, liquid-to-flask volume ratio, and substrate concentration, were examined in flask-scale experiments and obtained the highest titer of 3-HP at 4.4 g l⁻¹ in 48 h. When a fed-batch process was carried out in a bioreactor under pH-regulated conditions, the recombinant E. coli produced 3-HP at 31 g l⁻¹ in 72 h with a yield of 0.35 mol mol⁻¹ glycerol. The maximum specific rate of 3-HP production was estimated to be 3.41 mmol g⁻¹ cdw h⁻¹ between 12 and 24 h. Other than 3-HP, propionic acid (3.4 g l⁻¹), 1,3-propanediol (2.4 g l⁻¹), and lactic acid (1.6 g l⁻¹) were produced as the major by-products. This paper reports for the first time a commercially meaningful high titer of 3-HP production.