Abstract
Over two decades have passed since genetically modified prokaryotic cyanobacteria became capable of photosynthetically producing bioethanol. However, the limitation of low ethanol tolerance has impeded bioethanol production. In this study, the findings revealed that eukaryotic marine microalgae exhibited higher tolerance to ethanol compared to freshwater microalgae through a comparison of the growth performance of algal species under ethanol-induced stress. Specifically, the marine microalga Chlorella sp. MEM17 (MEM17) demonstrated tolerance to ethanol concentrations up to 6.0 % (v/v). Additionally, the polysaccharide and unsaturated fatty acid contents of MEM17 were considerably higher compared to ethanol-untreated control groups under ethanol stress. In conjunction with the comparative metabolomics approach, the remodeling of glycerophospholipid metabolic pathways was observed, specifically the conversion of a fraction of the reduced glycerophospholipids into specific glycerophospholipids, thereby enhancing the hindrance of ethanol entry into cells. The up-regulation of amino acid-related metabolic pathways aimed to augment the relative content of specific metabolites, such as gamma-aminobutyric acid (GABA), with the objective of scavenging intracellular reactive oxygen species (ROS). Furthermore, bolstered properties of the cell wall potentially facilitated by the increased polysaccharide content of MEM17 further impeded the potential entry of ethanol into the cell, while excess polysaccharide assisted in scavenging intracellular ROS. This study represents the first discovery of a high-concentration ethanol-tolerant eukaryotic marine microalga and its key metabolic pathways, with potential as “marine photosynthetic cell factories” for bioethanol production.
Published Version
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