Improved Growth and Metabolite Production in Chlorella sorokiniana under Mixotrophic Conditions with Acetate and Urea

In this study, changes in the growth and biochemical parameters of Chlorella sorokiniana under mixotrophic culture conditions with 50 mM acetate and acetate supplemented with 0.25, 0.50 and 1 mM of urea were investigated. Acetate increased fresh (FW) and dry (DW) weights by 54 and 40%, respectively, compared with the control. Acetate treatment also increased the amount of chlorophyll a and carotenoids by 2.93 and 3.32 times, respectively, compared with the control, but decreased the amount of chlorophyll b, protein, and soluble sugars. There was a significant increase in growth and in the amount of metabolites analyzed when urea was used together with acetate. The most suitable concentration of urea for increasing FW and DW, chl a and b, and protein was 1 mM, for increasing carotenoid 0.25 mM and for increasing soluble sugars 0.50 mM. The best results in the simultaneous treatment with acetate and urea for each of the parameters analyzed were as follows: carotenoid 5 times, FW 2.1 times, DW 2.5 times, chl a 3.35 times, chl b 2 times, protein 1.4 times and soluble sugar 1.3 times increase compared with the control. These results showed that the simultaneous use of a carbon source (acetate) and a nitrogen source (urea) was more effective in increasing growth and the amount of metabolites.