Polyhydroxybutyrate production by Paracoccus denitrificans using residual biomass from wastewater treatment photobioreactors

Abstract

Nowadays, the sustainability is one of the common goals of any project, especially in terms of fossil resources consumptions. One of the most used products from petroleum are the plastics with an annual production of around 400 million tons (Bera et al., 2023). Another issue is the high amount of residues, specifically biomass, that are generated in the wastewater treatment plants during the biological processes. Depending on the type of biological reactor, this biomass may consist of bacteria or, in the case of photobioreactors, a mixture of microalgae and bacteria, but they are always an interesting source of proteins, carbohydrates and other useful compounds, for example, for the production of bioplastics (Rojo et al., 2021). Polyhydroxyalkanoates (PHA) are biopolymers that have similar properties to the conventional plastics and that can be produced by several microorganisms by bacterial fermentation (Pagliano et al., 2021). Bacteria can metabolize a carbon source into PHA granules under stress condition, as can be under nitrogen limitation. In this work, the production of Polyhydroxybutyrate (PHB), one of the most known PHA was studied using the residual biomass from a wastewater treatment photobioreactor. The bacteria used for this purpose was Paracoccus denitrificans, and the biomass was composed of a consortium of microalgae (Scenedesmus almeriensis) and bacteria grown in swine wastewater.