META-ANALYSIS OF CARBON–NITROGEN STOICHIOMETRY EFFECTS ON POLYHYDROXYBUTYRATE (PHB) ACCUMULATION IN ACTIVATED SLUDGE AND MIXED MICROBIAL CULTURES

Abstract

Polyhydroxy butyrate (PHB) that is a biodegradable biopolymer that can possibly be utilized in producing bioplastics. In this meta-analysis, PHB is produced in comparison to pure cultures, enriched mixed microbial cultures (MMCs) and waste activated sludge (WAS) systems. With the help of random-effects models we will estimate the pooled PHB yields and comment on the results of carbon to nitrogen (C:N) ratio and time on accumulation. The PHB gave the highest (70.0%), then enriched MMCs (33.5%), WAS (31.9%) and these were very diverse as it was a multitude of microbes. Production of PHB was found to increase in all the systems but the peak response has been observed in the pure cultures and this has been attributed to the fact that the C:N ratios are escalating. Time analysis showed that PHB accumulation increased with time where pure cultures resulted in the greatest production then the enriched and finally, the WAS. The consequence of this is that pure cultures would be the most appropriate and possibly the most ideal in the production of PHB yet, enriched MMCs and WAS systems would also make good potential production options which can be scaled at any time. Optimization of microbial selection and nutrient management of such systems would be the critical conditions of enhancing PHB. These strategies will be improved in the future to ensure that the wastewater biomass uses the least amount of energy to produce PHB.