Kinetic modelling of 2,3-butanediol production by Raoultella terrigena CECT 4519 resting cells: Effect of fluid dynamics conditions and initial glycerol concentration.

Abstract

Biodiesel-derived glycerol was biologically converted to 2,3-butanediol, an organic compound with multiple industrial applications. Recent studies showed that Raoultella terrigena CECT 4519 is an effective biocatalyst for the bioprocess under conventional growing conditions. In the present work, a novel biocatalyst composed by R. terrigena resting cells was evaluated for the first time. Fluid dynamic conditions has been optimized to maximize 2,3-butanediol production in terms of titre, yield, and selectivity. Regarding the effect of initial glycerol concentration in batch runs, no substrate inhibition was detected in the studied conditions (concentrations between 45 and 250 g/L were used). Employing pure glycerol as carbon source, 82.0 g/L 2,3-butanediol titre was achieved, whereas 76.5 g/L were reached using raw glycerol. These numbers involve an achieved yield respect to maximal theoretic yield of 79% and 77%, respectively. A successful kinetic modelling of the bioprocess was developed and it is able to describe both the evolution of concentrations of relevant components with time and the rates calculated at experimental time values. Estimated specific 2,3-butanediol production rate was 0.034 g2,3-BDO/gX⋅h, while the estimated empirical pseudo-stoichiometric coefficient glycerol/2,3-butanediol was 2.52 gGly/g2,3-BDO. The obtained results showed that R. terrigena resting cells is a promising biocatalyst, which provides new opportunities for developing and scaling-up glycerol biorefineries.