Nitrogen removal affect lipid production and expression levels of accD gene through cultivation of Chlorella in synthetic wastewater

Microalgae are considered to be a potential feedstock for biodiesel production. The study resulted in developing an integrated lipid enhancement strategy by culturing C-hlorella vulgaris in wastewater containing nitrogen and phosphorus. An ideal experimental design was carried out based on central composite design (CCD) with response surface methodology (RSM). This RSM was used to calculate the effects of nitrogen and phosphorus concentration, and their interaction with nitrogen removal and accD gene expression corresponding to lipid synthetize. ACCase with four subunits is the key enzyme for fatty acid synthesis which expression of the beta subunit ( accD ) synthesized in the chloroplast is decisive to the levels of heteromeric ACCase . Under this experimental design there were 13 different runs with various concentrations of nitrogen and phosphorus. Based on the analysis of variance (ANOVA), the nitrogen removal and gene expression model proved to be of very good fit with a very low probability value (< 0.0001). Optimum nitrogen removal (50.5%) and accD gene expression (8.5-fold) occurred at low nitrogen concentration (100 mg/L) and maximum phosphorus concentration (100 mg/L).