Renewable biomass production by mixotrophic algae in the presence of various carbon sources and wastewaters

This study evaluated mixotrophic growth potential of native microalgae in media supplemented with different organic carbon substrates and wastewaters. Three robust mixotrophic microalgae viz. Chlamydomonas globosa, Chlorella minutissima and Scenedesmus bijuga were isolated after long-term enrichments from industrial wastewater. The mixotrophic growth of these microalgae resulted in 3–10 times more biomass production relative to phototrophy. Glucose, sucrose and acetate supported significant mixotrophic growth. Poultry litter extract (PLE) as growth medium recorded up to 180% more biomass growth compared to standard growth medium BG11, while treated and untreated carpet industry wastewaters also supported higher biomass, compared to BG11 growth with no significant effect of additional nitrogen supplementation. Supplementing treated wastewater and PLE with glucose and nitrogen resulted in 2–7 times increase in biomass relative to the unamended wastewaters or PLE. The consortia of Chlamydomonas–Chlorella and Scenedesmus–Chlorella were the best for PLE and untreated wastewater respectively, while a combination all three strains was suitable for both PLE and wastewater. These algae can be good candidates for biofuel feedstock generation as they would not require freshwater or fertilizers. Such mixotrophic algal consortia offer great promise for production of renewable biomass for bioenergy applications using wastewaters.