Utilisation of Desmodesmus subspicatus LC172266 for simultaneous remediation of cassava wastewater and accumulation of lipids for biodiesel production

In view of the current demand for bioenergy and environmental sustainability, utilisation of Desmodesmus subspicatus LC172266 for simultaneous remediation of cassava wastewater and accumulation of lipids for biodiesel production was investigated. The microalga was grown under photoautotrophic, heterotrophic and mixotrophic culture conditions using Bold's Basal Medium (BBM) and cassava wastewater as substrates. Results showed that biomass accumulation under unoptimised autotrophic, heterotrophic and mixotrophic growths conditions were 0.217, 0.63 and 1.042 g/L, respectively. The lipid contents were 15.86, 21.40 and 24.70%, respectively. Fatty acid profiles revealed that although the most abundant compounds under autotrophic conditions were those recommended for biodiesel production, oleic acid eluted under mixotrophic (19.61%) and heterotrophic (10.25%) conditions exhibited more acceptable biodiesel quality. The physical properties of the fatty acid methyl esters (FAMEs) also meet the required biodiesel standards. The percentage reduction in total dissolved solids (TDS, 84.04), electrical conductivity (EC, 82.31), biochemical oxygen demand (BOD, 85.85) and chemical oxygen demand (COD, 89.04) under heterotrophic cultivation were more favourable than their respective mixotrophic values (80.56, 74.63, 62.22, and 51.39%). Although the lipid accumulation of the microalga under mixotrophic conditions was greater, bioremediation potential of cassava wastewater was more favourable under heterotrophy.