Accelerated production of 1,3-propanediol from glycerol by Klebsiella pneumoniae using the method of forced pH fluctuations

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Abstract
1,3-Propanediol (1,3-PD) is a bivalent alcohol, used in a number of chemical syntheses. It could be produced from glycerol in course of microbial fermentation by Klebsiella pneumoniae along with more than five minor liquid products. With the purpose to enhance 1,3-PD production and to eliminate by-products formation, principally new pH control on the process was applied. The method, named “forced pH fluctuations” was realized by consecutive raisings of pH with definite ΔpH amplitude (ranging from 1.0 to 2.0) at time intervals between 2 and 4 h, during a series of fed batch processes. The fermentation performed by forced pH fluctuations with ΔpH = 1.0, risen at every 3 h was evaluated as the most successful. Increase by 10% of the maximal amount of 1,3-PD (g/l), 22% higher productivity [g/(l h)], and 29% increase in 1,3-PD molar yield were achieved, compared to the referent fed batch (with constant pH = 7.0). In addition, significant decrease in by-products formation was obtained. The most important reduction was observed in the lactic and acetic acids yields, where 50 and 70% decrease were reached. The results suggested the potential of pH to manage the share and quantity of product spectrum in mixed diols–acids fermentations. The application of “forced pH fluctuations method” achieves the desirable increase in 1,3-PD formation and decrease in by-products accumulation at the same time by a comparatively simple approach by adjustment of one bioprocess parameter only.

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