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Mixed culture of Chlorella sp. and wastewater wild algae for enhanced biomass and lipid accumulation in artificial wastewater medium

Gopalakrishnan, Kishore, Roostaei, Javad, Zhang, Yongli
Frontiers of environmental science & engineering 2018 v.12 no.4 pp. 14
Chlorella, algae, algae culture, biofuels, biomass production, carbon dioxide, coculture, cost effectiveness, feedstocks, fluorescence, light intensity, lipids, mixed culture, response surface methodology, wastewater
The purpose of this work is to study the co-cultivation of Chlorella sp. and wastewater wild algae under different cultivation conditions (i.e. CO₂, light intensity, cultivation time, and inoculation ratio) for enhanced algal biomass and lipid productivity in wastewater medium using Response Surface Methodology (RSM). The results show that mixed cultures of Chlorella sp. and wastewater wild algae increase biomass and lipid yield. Additionally, findings indicate that CO₂, light intensity and cultivation time significantly affect algal productivity. Furthermore, CO₂ concentration and light intensity, and CO₂ concentration and algal composition, have an interactive effect on biomass productivity. Under different cultivation conditions, the response of algal biomass, cell count, and lipid productivity ranges from 2.5 to 10.2 mg/mL, 1.1 × 10⁶ to 8.2 × 10⁸ cells/mL, and 1.1 × 10¹² to 6.8 × 10¹² total fluorescent units/mL, respectively. The optimum conditions for simultaneous biomass and lipid accumulation are 3.6% of CO₂ (v/v), 160 µmol/m²/s of light intensity, 1.6/2.4 of inoculation ratio (wastewater-algae/Chlorella), and 8.3 days of cultivation time. The optimal productivity is 9.8 (g/L) for dry biomass, 8.6 E + 08 (cells/mL) for cell count, and 6.8 E + 12 (Total FL units per mL) for lipid yield, achieving up to four times, eight times, and seven times higher productivity compared to nonoptimized conditions. Provided is a supportive methodology to improve mixed algal culture for bioenergy feedstock generation and to optimize cultivation conditions in complex wastewater environments. This work is an important step forward in the development of sustainable large-scale algae cultivation for cost-efficient generation of biofuel.