Optimization of the mixotrophic culture medium composition for biomass production by Chlorella vulgaris using response surface methodology.

Response surface methodology was adopted to optimize the mixotrophic culture medium composition for biomass production.In the first optimization step,KNO3,glucose and NaCl were screened from eleven related nutrients as the major factors influence the mixotrophic growth of Chlorella vulgaris significantly using Plackett-Burman design.Subsequently,quadratic regression equation model was established based on the Box-Behnken design,and the optimized nutrients contents were that KNO3 was 1.64g/L,glucose was 45g/L and NaCl was 1.57g/L.The predicted maximum biomass content of 5.28g/L was obtained from the model,and the actual validation value was 5.68g/L.The validation results indicated that the model can be used to optimize the mixotrophic culture medium of C.vulgaris for its high prediction accuracy.Under the optimum conditions,the biochemical composition of mixotrophic C.vulgaris displayed that the protein and total pigments content were reduced and the soluble carbohdyrate and lipid content were increased,compared with the un-optimized algal biomass.The major fatty acids of the alga lipid were oleic acid and palmitic acid.The results from biochemical composition analysis suggested that the mixotrophic biomass of C.vulgaris can be used as a potential feedstock for microalgae biofuel production.