Abstract
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•A novel cyanobacterium strain was characterized for biorefinery applications.•The highest biomass productivity and CO2 fixation was achieved under summer conditions.•The biomass produced in summer was shown to be rich in lipids and carbohydrates.•The biomass produced in winter showed the highest protein productivity.•A 180–198 mgg−1 of phycobilin content was achieved.
Cultivating photosynthetic microbes in city wastewater may help to achieve environmental sustainability owing to concomitant pollutant removal, biological transformation of the nutrients into bioproducts, and atmospheric carbon fixation. Cyanobacteria are the most efficient photosynthetic fixers of atmospheric carbon along with the microalgae. The present study was focused on optimizing the growth conditions for a newly isolated filamentous cyanobacterium Plectonema terebrans BERC10 to achieve enhanced biomass and metabolite productivity for a multiproduct biorefinery using various compositions of synthetic wastewaters. Higher biomass productivity of 140 mg L−1 d−1 (dried mass) with CO2 sequestration rate of 250 mg L−1 day−1 was achieved by mimicking the summer (32 ± 2 °C) cultivation conditions, which was further favored by the wastewater-derived alkalinity (pH 10.0–11.0). The biomass produced was rich in carbohydrates and lipids, having 58.68 mgg−1d−1 and 39.25 mgg−1d−1 of carbohydrate and lipid productivities, respectively. While winter cultivation conditions (22 ± 2 °C) favored higher protein productivity (34.49 mgg−1d−1) when compared to summer conditions. Additionally, in response to excessive nutrients and alkalinity (pH 10.0), it produced 180-198 mgg-1 of phycobilins. Considering the multiproduct concept, the phycobilins were extracted and lipids from the residual biomass were converted to biodiesel and analyzed by gas chromatography-mass spectrometry (GC–MS). Intrestingly, phycobilin extraction had no negative impact on the quality and content of the biodiesel in the residual biomass. These features make the Plectonema terebrans BERC10 a promising candidate for the biological transformation of wastewater derived nutrients to biofuels and bioproducts.