Transesterification - induced extraction of biodiesel from heterotrophic marine microalga Chlorella salina

Abstract

Extraction of biodiesel from marine microalga Chlorella salina grown under two different conditions viz., photoautotrophic and heterotrophic culture systems were compared. A remarkable growth increment of C. salina due the influence of glucose in the heterotrophic basal medium was observed. Heterotrophic growth of C. salina resulted in the accumulation of high lipid content (52%) in algal cells. The cells grown in two different culture conditions were harvested by pH adjustment method. The cells recovered were dried and the maximum yield in relatively shorter duration was recovered at 60 °C. The maximum quantity of microalgal oil was extracted from heterotrophic algal powder using chloroform: methanol combination. Biodiesel was extracted from the microalgal oil through acidic transesterification using different molar ratios of methanol to biolipid oil with different catalyst quantities (sulphuric acid) and at different temperatures. The process combination of acidic transesterification of microalgal lipid oil in the presence of 100% acid catalyst quantity for the methanol to oil molar ratio of 55:1 at a temperature of 50 °C was proved to be effective for the extraction of good quality biodiesel. The biodiesel product derived was compared against the ASTM standards for biodiesel.