Mechanism study on the regulation of metabolite flux for producing promising bioactive substances in microalgae Desmodesmus sp.YT through salinity stress

Desmodesmus sp.YT rich in bioactive substances exhibited impressive tolerance to various environmental conditions. To investigate the metabolism transformation influenced by salt stress in Desmodesmus sp.YT, biochemical compositions and comparative transcriptome were thoroughly explored in this research. Results showed that normal treatment (0‰ salinity) was beneficial for the production of biomass (up to 1.87 times) and protein (up to 1.46 times), compared with salt treatment. Furthermore, differentially expressed genes analysis revealed that vital genes involved in photosynthesis (light-harvesting complexs, LHCs; photosystem II oxygen-evolving enhancer proteins, Psbs), C3 photosynthetic pathway (fructose-bisphosphate aldolase, ALDO; fructose-1,6-bisphosphatase, PFK; phosphoglycerate kinase, PGK) and chlorophyll synthesis (coproporphyrinogen III oxidase, CPOX; porphobilinogen synthase, HemB) were significantly up-regulated in 0‰ salinity, leading to enhanced cell growth. Interestingly, salt stress stimulated the expression of cellulose synthase catalytic subunit A2 (CesA2) and starch synthase (GLGA), increasing the biosynthesis of cellulose (up to 3.23 times) and starch (up to 1.05 times). Results showed that Desmodesmus sp.YT cultured at freshwater could be applied as feed additives while microalgae grown in seawater had the potential for biofuel production for further mass cultivation. Copyright © 2022 The Authors. Published by Elsevier B.V.