Enhanced growth of Chlorella sorokiniana on ash-enriched treated wastewater for large-scale lipid and chlorophyll a production using a hybrid raceway photobioreactor.

Abstract

Nutrient concentration in microalgal cultivation media greatly influences microalgal growth and macromolecules production. In the present study, treated urban wastewater was used as a medium for Chlorella sorokiniana, incorporating mineral components and ashes in batch culture. The aim was to assess the combined effect of nutrients on microalgal growth, Chlorophyll a content, and lipid production using customized experimental design and response surface methodology. Another objective was to evaluate response improvement after using hybrid raceway photobioreactor HRPBR. The results showed that the highest microalgal biomass growth as well as the highest Chlorophyll a and lipid concentrations was obtained using 2015 mg. L^-1of NaNO₃ and 2086.76 mg. L^-1 of NaHCO₃ with a mineral solution concentration of 120 mg. L^-1. After the HRPBR cultivation, Chlorophyll a content increased from 40.26 to 65.04 mg. L^-1 and the lipid content rose from 37 to 40% and then to 68% under starvation conditions. In these circumstances, the FA profile of Chlorella sorokiniana became in line with the requirements of the European biodiesel standard. Thus, the low-cost nutrient sources for culture medium formulation can be used to culture C. sorokiniana as an efficient strain for sustainable and cost-effective biofuel production.