Ethyl oleate synthesis using Candida rugosa lipase in a solvent free system.Role of hydrophobic interactions.

GUSTAVO TRUBIANO; DANIEL BORIO; MARÍA LUJÁN FERREIRA

BIOMACROMOLECULES

Año: 2004 vol. 5 p. 1832 - 1840

1525-7797

The solvent-free esterification reaciton of a commercial oleic acid and ethanol was selected as the test reaction for Candida rugosa immobilized on polypropylene (PP) at 318 K (initial molar ratio 1:1).Adding of wter from 0 to 30 % wt. % (in gram per gram of fatty acid x100) and the pretreatment  of Candida rugosa with polyethylenglycol (PEG), octane and acetone increases the conversion to ethyl esters.The role of hydrophobic interactions of the lipase with PP and PEG was studied using molecular mechanics (MM2) for calculation of steric energies and the parameterized model 3 (PM3) for calculation of enthalpies upon interaction. the non polar lateral groups of aminoacids interact strongly with PP, whereas polar groups interact more strongly with PEG.Both interactions stabilize the  open, active conformations of the lipase from Candida rugosa .Activities ranged from 5x10-5 to 2x10-4 molethyloleate/h/mg enzyme depending on reaction conditions.Steric energy changes vary between +30 and -10 Kcal/mol whereas the enthalpy changes ranged from +10 to -10 Kcal/mol.