Conversion of Chlamydomonas sp JSC4 lipids to biodiesel using Fusarium heterosporum lipase-expressing Aspergillus oryzae whole-cell as biocatalyst

Lipid from Chlamydomonas sp. JSC4 was used as a feedstock for biodiesel production. The lipid was found to contain high amounts of phospholipids and free fatty acid in addition to the triglycerides. Two enzymatic methods for the efficient conversion of the heterogenous lipid to fatty acid methyl esters (FAME) were carried out. The method using either a lipase cocktail containing Candida cylindracea lipase and Thermomyces lanuginosus lipase combination (m I) or immobilized Fusarium heterosporum lipase-expressing Aspergillus oryzae whole-cells (m II) were both successful. However, the method using lipase cocktail showed 30.8% relative stability after the fourth batch, whereas the whole-cell biocatalyst showed 98.1%. Although the whole-cell biocatalyst tolerated a wide range of water content, an exploration of the effect of water-methanol interaction on the biocatalytic process showed that 24% water and 7: 1 methanol to oil ratio is more favorable for FAME production. A higher initial methanol consumption rate facilitated a more stable system with the whole-cell biocatalyst, producing over 97% FAME in 32 h. The efficient conversion of a highly heterogenous substrate in the presence of high amounts of water could be an effective technique for the enzymatic conversion of microalgal lipids.