Poly- β-hydroxybutyrate production by Synechocystis MT_a24 in a raceway pond using urban wastewater

This study aimed to investigate PHB production in the cyanobacteriumSynechocystis sp. PCC6714 MT_a24 in an outdoor bioreactor using urban wastewater as a sole nutrient source. The culture was grown in a thin-layer raceway pond with a working volume of 100 L, reaching a biomass density of up to 3.5  g L−1 of cell dry weight (CDW). The maximum PHB content was found under nutrient-limiting conditions in the late stationary phase, reaching 23.7  ± 2.2% PHB per CDW. These data are one of the highest reported for photosynthetic production of PHB by cyanobacteria, moreover using urban wastewater in pilot-scale cultivation which multiplies the potential of sustainable cultivation approaches. Contamination by grazers (Poterioochromonas malhamensis) was managed by culturingSynechocystis in a highly alkaline environment (pH about 10.5) which did not significantly affect the culture growth. Furthermore, the strain MT_a24 showed significant wastewater nutrient remediation removing about 72% of nitrogen and 67% of phosphorus. These trials demonstrate that the photosynthetic production of PHB bySynechocystis sp. PCC6714 MT_a24 in the outdoor thin-layer bioreactor using urban wastewater and ambient carbon dioxide. It shows a promising approach for the cost-effective and sustainable production of biodegradable carbon-negative plastics.Key points• High PHB production by cyanobacteria in outdoor raceway pond• Urban wastewater used as a sole source of nutrients for phototrophic growt...
Source: European Journal of Applied Physiology - Category: Physiology Source Type: research