Production of polyhydroxybutyrate by pure and mixed cultures of purple non-sulfur bacteria: A review

Purple non-sulfur bacteria (PNSB), most commonly called photobacteria, are a group of photoheterotrophic bacteria well known for their ability to produce hydrogen while degrading several carbon substrates, such as organic acids and carbohydrates, as well as organic matter in wastewater and effluents from other processes, such as dark fermentation. Given that this group of photobacteria is also capable of accumulating polyhydroxybutyrate (PHB) as a storage compound, this review paper aims to present and discuss the different operational and nutritional conditions reported in the literature that favor PHB production by PNSB in order to guide the process conditions that should be used. A comparison of the accumulated PHB content among different PNSB strains on several carbon and nitrogen sources and concentrations is also outlined. This paper also addresses some future perspectives for PHB production, such as the use of wastewater as a substrate and mixed cultures to reduce economic costs and the environmental impact and make the PHB production process more profitable, sustainable and attractive.