Establishment of Stable Genetic Transformation Conditions for Novel Thermotolerant Scenedesmus sp. (Chlorophyta)

Abstract

Microalgae became an attractive source of high value compounds such as fatty acids, carotenoids and other nutrients in recent years. In a previous study, the characterization of a novel thermo-tolerant freshwater microalga, Scenedesmus sp. ME02 with high phenolic content, particularly rich in flavonoids was done. Here, two different approaches are reported to increase the efficiency of the growth parameters of this strain. Firstly, the effects of phosphorus (P) depletion on biomass and lipid characteristics of Scenedesmus sp. ME02 were investigated. Although, P depletion resulted in a slight reduction in biomass productivity of microalgae and had a minimal effect on the lipid content and productivity; fatty acid methyl ester profile changed substantially. Particularly, percent oleic acid (18:1) increased by more than two-fold, whereas percent linolelaidic acid (C18:2n6t) and linolenic acid (C18:3n6) decreased significantly when cells were switched from P-replete (control) to P-deplete conditions. Overall, the polyunsaturated fatty acid content was significantly reduced. Secondly, stable genetic transformation conditions for Scenedesmus sp. ME02 via electroporation were optimized using two different transformation vectors. GFP gene expression was detected in colonies transformed with both vectors by RT-PCR. GFP protein expression was detected in the transgenic lines one year after initial transformation by confocal microscopy.