Decaying exponential feeding of nonanoic acid for the production of medium-chain-length poly(3-hydroxyalkanoates) by Pseudomonas putida KT2440.

Decaying exponential feeding strategies for the production of medium-chain-length poly(3-hydroxyalkanoates) by Pseudomonas putida KT2440 have been developed as a method of delaying oxygen limitation that is typically responsible for the termination of high cell density aerobic fermentations. Two feeding strategies were evaluated to control the biomass generation rate and consequently control the oxygen uptake rate of the cells. A linear decaying strategy allowed the production of 90 g L–1 dry biomass containing 65% PHA in 31 h with a cumulative productivity of 1.9 g L–1 h–1, while a quadratic decaying exponential feeding rate followed by a constant feeding rate produced 109 g L–1 of dry biomass containing 63% PHA. The latter methodology improved the cumulative PHA productivity to 2.3 g L–1 h–1, which is the highest MCL-PHA productivity ever reported. Analysis of the relationship between the final biomass concentration and the associated maximum cell generation rate (which is directly related to the maximum oxygen transfer rate) indicated that higher biomass levels could be attained by decreasing the substrate feeding rate at high biomass concentrations. [ABSTRACT FROM AUTHOR]