Selection of a Carbohydrate-rich Microalgae and Its Molecular Identification

Microalgae are an ideal raw material for bioethanol production because of fast growth and high carbohydrate productivity. Ten pre-selected microalgae strains were cultivated in an air-bubble column photobioreactor to test the characteristics of carbohydrate production, and carbohydrate productivity was used as the key parameter to select the strains suitable for carbohydrate production. Results showed that biomass, soluble sugar content, total carbohydrate content and carbohydrate productivity of the tested strains were in the range of 0.922 - 1.965 g/L, 4.42% - 19.23%, 26.8% - 60.9% and 36.17 - 149.67 mg·L^-1·d^-1, respectively. Both carbohydrate productivity (149.67 mg·L^-1·d^-1) and soluble sugar content (19.23%) of GZ-57 were the highest among the investigated strains, and GZ-57 was selected as the candidate strain with greatest potential in bioethanol production. Morphological observation and molecular phylogenetic analyses of 18S rDNA gene sequences and internal transcribed sequences (ITS) indicated that GZ-57 belonged to the Desmodesmus genus, and was identified as Desmodesmus maximus.