9 / 2021-06-06 01:10:06

Concomitant production of polyhydroxyalkanoates (PHA) and extracellular polymeric substance (EPS) using wastes

Bioplastics, exopolysaccharides, co-products, circular economy, wastes, sludge, sustainability

The exploitation of petrochemical plastics is not only declining the global fossil fuels but also creating a havoc in the environment due to their non-biodegradable nature. Bioplastics such as polyhydroxyalkanoates (PHAs) are attractive alternatives to petro-plastics because of their biodegradability, thermoplastic, and mechanical properties. They can be produced by variety of microbial strains using pure and renewable substrates under certain unfavourable conditions like availability of carbon, limitation of nitrogen, oxygen, or phosphorus. The range of their properties can be controlled by choice of substrate, bacterial strains, fermentation conditions, and downstream processing. Concomitant production of other value-added products such as extracellular polymeric substances (EPS) along with PHA can improve the overall process economics.

EPS are polysaccharides produced by microbes during unfavourable conditions like that of PHA production. EPS generally protects the cells and acts as a nutrient source during stress conditions. Generally, the production of EPS is reported by microbial strains using synthetic media leading to high production cost thus, limiting their market applications. In this study, different strains isolated from pulp-paper activated sludge were tested for simultaneous production of PHA and EPS. The production of PHA and EPS was studied in 5L fermenters and later, the produced EPS was characterised in terms of flocculation activity, dewaterability, protein-carbohydrate content and functional groups using Fourier Transform Infrared Spectroscopy (FT-IR). The produced EPS could be used as flocculants for improving the wastewater treatment efficiency with significant role in pollutant removal, bio-flocculation, settling and dewatering of activated sludge. The presented work will improve our understanding in efficiently recovering two or more co-products that can be used for different environmental applications.