Optimization of the culture conditions of a Chlamydomonas high oil content ultraviolet mutant CC124-M25 and polymorphism analysis by inter-simple sequence repeat (ISSR)

Abstract

Microalgal oils have been considered as a promising feedstock for biodiesel production, which can potentially completely substitute fossil fuels. In the present study, 4500 mutants were obtained from Chlamydomonas reinhardtii CC124 through ultraviolet (UV) induced mutagenesis. After screening these mutants using HSM and HSM-N media, a mutant CC124-M25 with high oil content was selected under an HSM-N medium condition. Compared with the wildtype CC124, the mutant CC124-M25 has a similar growth rate, but the oil content increased by 10%, reaching up to 42%, which has a good prospect for biodiesel production. Optimization studies showed that the nitrogen-free medium with 20 mmol/L potassium element, called N0P20 medium is the most suitable for oil accumulation in the mutant, in which the oil content can reach a maximum of 0.5 g/g. The oil content of the mutant cells grown in the medium contain 2 g/L sodium acetate also can reach a maximum of 0.5 g/g , suggesting that 2 g/L sodium acetate is optimum for oil accumulation. In addition, ISSR markers were used to analyze the difference between the mutant CC124-M25 and the wildtype CC124. In total, 4 out of 100 primers could amplify distinct bands with good polymorphsim. The results showed that the polymorphism information content or CC124 was 78% and that for the mutant CC124-M25 was 50%, suggesting the genetic stability of the mutant obtained by UV mutagenesis. Key words: Chlamydomonas reinhardtii, UV mutagenesis, orthogonal, inter-simple sequence repeat (ISSR)