Enhanced growth and lipid production of microalgae under mixotrophic culture condition: effect of light intensity, glucose concentration and fed-batch cultivation.

Microalgae capable of accumulating high lipid content were screened in photoautotrophic, heterotrophic and mixotrophic cultures. The biomass and lipid production of all tested strains in mixotrophic culture were notably enhanced in comparison with photoautotrophic and heterotrophic cultures. Among the tested strains, marine Chlorella sp. and Nannochloropsis sp. were ideal candidates for biodiesel production because of their high lipid production. The influence of light intensity and initial glucose concentration on growth and lipid content of both strains were investigated. Although increasing light intensity and initial glucose concentration enhanced the growth of both strains, it reduced their lipid content. To produce a high amount of biomass with high lipid content, a fed-batch cultivation with stepwise increasing light intensity was performed. The lipid production by this strategy was approximately twice that of conventional batch cultivation. The main fatty acid compositions of the two microalgae were C16-C18 (>80%) which are appropriate for biodiesel production.