Temperature and nutrient coupled stress on microalgal neutral lipids for low‐carbon fuels production

A freshwater Chlorella sp. was cultured at temperatures from 10 to 45 degrees C and synergistic stress was employed by using selective and complete nutrient depleted growth media. Temperature fluctuations were found to have a significant effect on the microalgae physiology. The optimum temperature of 35 degrees C shows suitability for growth in a sub-tropical climate. The fatty acid methyl esters' (FAMEs') composition was significantly altered when cultures were incubated under various pre-determined stress conditions. The effect of dual stress was found to have the greatest increase in the lipid yield, averaging 55% (w/w). The majority of the identified FAMEs (C-16 and C-18) showed the potential for quality biodiesel and aviation fuel due to the characteristics of FAME. This study is relevant for commercial-scale biodiesel production and the technologies developed would improve the economic feasibility and potential of microalgal biomass feedstock for biodiesel production by transesterification. There is also high potential for low-carbon jet fuel by thermal cracking or pyrolysis and fractionation of crude-bio-oil from Chlorella sp. These processes will convert carbon chains or FAMES in the C-14 to C-16 range, which is appropriate for low-carbon jet fuel. It is therefore possible to generate biodiesel and aviation fuel from Chlorella sp. cultivated in freshwater at achievable temperatures in a sub-tropical environment under total nutrient deprivation, aiming to stimulate a bio-oil increase. (c) 2021 Society of Industrial Chemistry and John Wiley & Sons Ltd.