Process strategies for enhanced production of 1,3-propanediol by Lactobacillus reuteri using glycerol as a co-substrate

• Production of 1,3-propanediol in batch, repeated batch and chemostat process.
• Repeated batch cultivations with cells decantation with high productivity and yield on glycerol.
• The PDO production in repeated batch with cells decantation seems to be reported for the first time in literature.
• High productivity of 1,3-propanediol under a yield on glycerol near the theoretical.
• High productivity, 4.92 g L−1 h−1, of 1,3-propanediol by Lactobacillus sp.

1,3-Propanediol (PDO) is a bulk chemical used in the synthesis of polymers for terephthalates, cosmetics and lubricants, among other things. PDO can be produced by microorganisms growing anaerobically on glycerol. The objective of this study was to analyze the behavior of Lactobacillus reuteri ATCC23272 when cultivated in batch, repeated batch and continuous modes during the conversion of glycerol into 1,3-propanediol, with regards to the main parameters for viable industrial production: productivity (QPDO), PDO concentration and yield on glycerol (YPDO/GLY). Cultures were performed in an MRS medium with glucose and glycerol as co-substrates, at 37 °C. Besides the bioreactor operation mode, the following features were evaluated: anaerobiosis, limited oxygen respiration, pH 5.5 and 6.2. In batch mode, the best condition was anaerobiosis at pH 5.5, which resulted in YPDO/GLY and QPDO of 0.66 gPDO gGLY−1 and 1.42 g L−1 h−1, respectively. In repeated batch mode, the highest level of productivity was 4.12 g L−1 h−1, when cells were first decanted and 80% of the liquid phase was replaced with fresh medium. In chemostat mode, YPDO/GLY of 0.70 gPDO gGLY−1 was achieved and productivity in the steady state was 20% higher (4.92 g L−1 h−1), compared to the best result in the repeated batch mode. The highest PDO productivity, QPDO, in chemostat mode, was due to the highest rate of glucose consumption, which can be directly related to PDO productivity.