Joint production of biodiesel and bioethanol from filamentous oleaginous microalgae Tribonema sp.

Making full use of lipid and carbohydrate in microalgae for joint production of biodiesel and bioethanol may create a potential way to cut the high cost of single biofuel production from microalgae. Compared with conventional unicellular oleaginous microalgae, filamentous microalgae Tribonema sp. is richer in lipid and carbohydrate contents and lower protein content, thus, this study explores the suitability of Tribonema sp. as a substrate for joint production of biodiesel and bioethanol. Acid hydrolysis is the key step to saccharify wall cell into fermentable sugar and release lipid. Microalgae biomass (50 g/L) was acid (3% H2SO4) hydrolyzed at 121 °C for 45 min to reach the maximum hydrolysis efficiency (81.48%). Subsequently, the lipid separated with hexane–ethanol from the hydrolysate was converted into microalgae biodiesel and the conversion rate was 98.47%. With yeast Saccharomyces cerevisiae, the maximum ethanol yield of 56.1% was reached from 14.5 g/L glucose in hydrolysate.