Research on pH control strategy in the bioconversion of glycerol to 1, 3-propanediol

The fermentation process of 1, 3-propanediol (1, 3-PD) by Klebsiella pneumoniae with glycerol as substrate was researched both in batch and fed-batch system. The declining pH during this course led to a great many disadvantages to the growth of microorganism, and had a negative effect on the production of 1, 3-PD. In order to increase 1, 3-PD yield and to reduce byproduct formation, experiments were conducted in which different ratios of ammonia and glycerol mixtures were used for pH control as well as for supplementation of glycerol. During this course, an important phenomenon was noticed in that the yield of two main byproducts, 2, 3-butanediol and lactate, were closely related to pH. When pH was at 5.0 to 6.0, the main byproduct was 2, 3-butanediol, however, when pH was at 7.1 to 8.0, the major byproduct changed to be lactate. Based on the different pH effect on the composition of the byproducts in the broth, a kind of pH control strategy was applied during which pH fluctuated between 6.3 and 7.3 periodically and at last the maximum concentration of 1, 3-PD reached 70 g/L.