Dark mode of microalga — A sustainable and economical solution for microalgal biofuel production and waste treatment

Abstract

The heterotrophic mode, along with recyclable wastewater, plays a crucial role in addressing water shortages and limitations in trophic cultivation to produce valuable microalgal biomass and energy. In this study, Chlorella sorokiniana AARL G015 was cultivated in a waste-based medium, using response surface methodology to enhance biomass production and reduce costs. Robust growth was observed in a mixture comprising 39.45 % wastewater and 57.03 mL/L molasses, resulting in an impressive 80 % reduction in production costs compared to the traditional BG11 medium. This microalga exhibited the highest biomass production (3.5 g/L) and a lipid content of 19.94 %. Under dark conditions, the utilization of wastewater demonstrated the strain's efficient exploitation of waste resources and its potential for biodiesel applications. Furthermore, wastewater treatment exhibited significant efficiency in removing nutrients, particularly nitrogen, with levels reaching up to 99 %. These findings contribute significantly to the expansion of knowledge on microalgal heterotrophic cultivation for sustainable biofuel production.