Increasing lipid production of Desmodesmus sp. through atmospheric and room temperature plasma orientated with malonic acid: Performance and biochemical mechanism

Abstract

Desmodesmus sp. strain b15 with a high lipid yield was obtained through atmospheric and room temperature plasma (ARTP) mutagenesis orientated by malonic acid (MA) resistance screening. Key enzyme activity and gene expression were measured to elucidate the biochemical mechanisms regulating the high lipid synthesis of the mutant algal strains. MA further significantly enhanced the screening efficiency of the targeted lipid-rich algal strains mutated by ARTP, where the number of potential target algal strains was 3.5 times higher than the mutant strains by single ARTP. The triglyceride and total lipid content of strain b15 reached 330.21 and 373.27 mg L−1, which were 48.98% and 114.99% higher than the mutant a17 strain from single ARTP and the control strain, respectively. The maximum quantum yield (Fv/Fm) and relative electron transport rate (ETR) for the photosynthetic activity of b15 were lower than the control group. Additionally, the activities of acetyl-CoA carboxylase (ACCase) and diacylglycerol acyltransferase (DGAT) related to triglyceride synthesis were higher in b15, but malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) were greatly inhibited in the tricarboxylic acid cycle (TCA) by MA. The expressions of key regulatory genes of accD and dgat7566 for lipid synthesis in mutant b15 were also significantly higher than those in a17 and the control group (P < 0.05), and the decreased expression of SDH2 in the TCA also verified the superior lipid synthesis performance of strain b15.