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

Abstract

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.

Current developments on polyhydroxyalkanoates synthesis by using halophiles as a promising cell factory

“…Stanley et al optimized the nutritional requirements and process parameters for PHA production using Halomonas venusta KT832796 in 2-L bioreactor [87]. This strain produced CDW of 3.86 g/L containing 70.56% (wt) PHB at a volumetric productivity of 0.160 g/L/h by using glucose (20 g/L) and ammonium citrate (2 g/L).…”

“…This strain produced CDW of 3.86 g/L containing 70.56% (wt) PHB at a volumetric productivity of 0.160 g/L/h by using glucose (20 g/L) and ammonium citrate (2 g/L). A further fed-batch cultivation using four different feeding strategies was employed [87]. During carbon limitation, the pH value of medium increases due to build-up of ammonium ions [88].…”

“…During carbon limitation, the pH value of medium increases due to build-up of ammonium ions [88]. Thus, the first strategy was based on pH signal where feed pump was manually switched on as pH increased above 7.0 [87]. The PHB volumetric productivity significantly increased to 0.257 g/L/h but the PHB content decreased to 39.15% (wt) as the carbon flux got diverted towards biomass synthesis yielding CDW of 87.3 g/L.…”

A critical review: emerging bioeconomy and waste-to-energy technologies for sustainable municipal solid waste management

“…Aspergillus oryzae and Aspergillus awamori are known producers of glucoamylases, proteases, and phosphatases [133], and applying them in fungal hydrolysis, it was reported that glucose, free amino nitrogen and phosphate can be recovered from food waste [134]. Similarly, using Halomonas boliviensis, it was reported that polyhydroxyalkanoates can be produced from sugarcane molasses and bakery waste and food waste [135,136]. Polyhydroxyalkanoates are bio-based polymers that are gaining more attention in the bioeconomy, attributed to their biodegradability and thermoplastic properties similar to petroleum-derived plastics.…”

Ammonium Acetate Supplement Strategy for Enhancement of Chaetominine Production in Liquid Culture of Marine-Derived Aspergillus fumigatus CY018

“…The supplement of medium components as a significantly effective strategy was widely A C C E P T E D applied in the fermentation process for enhancing production of target metabolites. The nitrogen source as an important nutritional component affects the growth of microorganisms and synthesis of secondary metabolites [13]. On one hand, the effect of limiting nitrogen source can improve the production of secondary metabolites.…”