Effectiveness of ACh at the altered levels of phosphate buffer. (a-c) ACh improved the dry weight, lipid content, and lipid productivity of C. sorokiniana U2-9 at the altered phosphate buffer levels. (d) The highest ALA content was determined to be 272.43 ± 8 mg g-1 of dry weight at level A of phosphate buffer + ACh. (e) Biodiesel yield was increased up to 28.8 ± 2% at level B of phosphate buffer + ACh. Note: A-C describe the applied levels of phosphate buffer. A: Na2HPO4: 5.8 g L-1, KH2PO4: 3.63 g L-1, B: Na2HPO4: 11.62 g L-1 KH2PO4: 7.26 g L-1, C: Na2HPO4: 17.42 g L-1, KH2PO4: 10.89 g L-1. All data were given as mean ± standard error (n = 3) of three separate tests.