Conversion of volatile fatty acids into polyhydroxyalkanoate byRalstonia eutropha

Abstract

Aims: The aims of this study were to optimize condensed corn solubles (CCS) as a medium for growth of Ralstonia eutropha and to determine the effects of individual volatile fatty acids (VFAs) on polyhydroxyalkanoate (PHA) production. Methods and Results: A CCS medium of concentration 240 g l−1 with a carbon : nitrogen ratio of 50 : 1 was developed as the optimal medium. Cultures were grown in 1‐l aerated flasks at 250 rev min−1 at 30°C for 120 h. Comparable growth rates were observed in CCS vs a defined medium. At 48 h, VFAs were fed individually at different levels. Optimal levels of all the acids were determined to maximize PHA production. An overall comparison of the VFAs indicated that butyric and propionic acids provided the best results. Conclusion: An optimized CCS medium supported growth of R. eutropha. Butyric and propionic acids were the most efficient carbon sources to maximize PHA production when added at the 5 g l−1 level. Significance and Impact of the Study: The study shows that a byproduct of ethanol industry can be effectively used as a low cost medium for PHA production, thus partly reducing the cost of commercialization of biopolymers.

Development of a feeding strategy for high cell and PHA density fed-batch fermentation of Ralstonia eutropha H16 from organic acids and their salts

“…By the end of fermentation, accumulation of acetic acid in the media had occurred. These observations are in accordance with previous studies [13,23,40], showing R. eutropha favours consumption of butyric and propionic acid over acetic acid. Moreover Grousseau (2012) [41] demonstrated an antagonism in metabolism of acetic and butyric acid, which led to preferential consumption of butyric acid, depending on carbon fluxes directed to growth, as compared to fluxes going to PHA production.…”

PHA Productivity and Yield ofRalstonia eutrophaWhen Intermittently or Continuously Fed a Mixture of Short Chain Fatty Acids

“…Propionate utilization rate rose from 0.046 g L −1  h −1 in aerated shake flasks [23] to approximately 0.08 g L −1  h −1 when added as a part of the ARF mixture in the bioreactor trials. This was likely due to the higher cell populations achieved in the bioreactor trials coupled with the fact that proprionate utilization by R. eutropha is energetically favorable [31].…”

Utilization of Waste Carbon Source as Substrate and Economical Production of Biopolymer Polyhydroxyalkanoate Through Bacterial Consortia

“…Ralstonia eutropha or say Cupriavidus necator or Wautersia eutropha is a Gram-negative, lithoautotrophic organism (Pohlmann et al, 2006). C. necator can use volatile fatty acids (acetic, propionic and butyric acids) as its sole carbon and energy source for growth and Polyhydroxyalkanoate (PHA) synthesis (Du et al, 2002, Chakraborty et al, 2009 ). On the other hand, acetate and other short chain fatty acids inhibit cell growth and deteriorate the production of metabolites as they uncouple the transmembrane protein potential and thus interfere with the efficient energy metabolism (Shimizu et al, 2009).…”