An efficient lipid transesterification method for marine microalga Chlorella sp. BDUG 91771 has been ascertained. Among the homogeneous alkali (NaOH), homogeneous acid (H2SO4), heterogeneous alkali (CaO), heterogeneous acid (Fe-2(SO4)(3)) and two-step transesterification methods (NaOH and H2SO4 or H2SO4 and NaOH) tested with 100 mg lipid, 12-ml methanol, 2-h reaction time, reaction temperature 65 +/- 1 degrees C with stirring for 2 h, homogeneous acid catalysis was graded the best and its biodiesel yield was determined to be 45%. Of the different homogeneous acids tested, H2SO4 was regarded seamless. A maximum methyl ester yield of 60% was observed with 3.5% H2SO4, 2.5-h reaction time, which correlated well with the central composite design. Evidently, the spectra of H-1 NMR, C-13 NMR, FOR and GC-FID unveiled that biodiesel from Chlorella sp. BDUG 91771 encompasses fatty acid methyl esters (FAMEs). Gas chromatographic analysis revealed abundant palmitic acid, oleic acid and palmitoleic acid and it also had the desired Degree of Unsaturation (DU) of 56.33, Long Chain Saturated Factor (LCSF) of 1.97 and Cold Filter Plugging Point (CFPP) of -10.51. Further, density, viscosity, specific gravity, pour point, calorific value, acid value, total glycerol and ash content of algal biodiesel accords with the prescribed ASTM and European standard. (C) 2015 Elsevier Ltd. All rights reserved.