Two-step biocatalytic process using lipase and whole cell catalysts for biodiesel production from unrefined jatropha oil.

OBJECTIVE: To avoid lipase deactivation by methanol in the enzymatic transesterification process, a two-step biocatalytic process for biodiesel production from unrefined jatropha oil was developed.
RESULTS: Unrefined jatropha oil was first hydrolyzed to free fatty acids (FFAs) by the commercial enzyme Candida rugosa lipase. The maximum yield achieved of FFAs 90.3% at 40 °C, water/oil ratio 0.75:1 (v/v), lipase content 2% (w/w) after 8 h reaction. After hydrolysis, the FFAs were separated and converted to biodiesel by using Rhizopus oryzae IFO4697 cells immobilized within biomass support particles as a whole-cell biocatalyst. Molecular sieves (3 Å) were added to the esterification reaction mixture to remove the byproduct water. The maximum fatty acid methyl ester yield reached 88.6% at 35 °C, molar ratio of methanol to FFAs 1.2:1, molecular sieves (3 Å) content 60% (w/w) after 42 h. In addition, both C. rugosa lipase and R. oryzae whole cell catalyst in the process showed excellent reusability, retaining 89 and 79% yields, respectively, even after six batches of reactions.
CONCLUSION: This novel process, combining the advantages of enzyme and whole cell catalysts, saved the consumption of commercial enzyme and avoid enzyme deactivation by methanol.