Fed-Batch Strategies for Production of PHA Using a Native Isolate of Halomonas venusta KT832796 Strain.

In this study, polyhydroxyalkanoates (PHA) accumulation by Halomonas venusta
KT832796, a moderate halophilic bacteria isolated from marine source was studied. Both
nutritional requirements and process parameters for submerged cultivation of the organism in
bioreactor have been standardized. From the shake flask studies, glucose and ammonium
citrate as carbon and nitrogen source produced maximum PHA at a ratio 20 with 3.52 g/L of
dry cell weight and 70.56% of PHA content. However, ammonium sulfate as the nitrogen
source was found to be more suitable for fed-batch cultivation. Several feeding strategies
including pH-based fed-batch and variants of pulse feeding were studied to improve the PHA
levels. pH-based feeding, although improved PHA level to 26 g/L, most of the carbon flux was
diverted towards biomass formation; hence, the percent PHA was only 39.15% of the dry cell
weight. Maximum PHA of 33.4 g/L, which corresponded to 88.12% of the dry cell, was
obtained from high concentration single pulse method. There was a net 8.65-fold increase in
PHA using this feeding strategy when compared to batch studies. According to our knowledge,
this is the highest amount of PHA reported for a Halomonas venusta strain.