Abstract
Alcoholysis of oils mediated by immobilized lipases are limited by mass transfer effects on substrates. In this work, Novozym (R) 435 lipase was subjected to seven different chemical derivatizations. The effects of changes in the enzyme surface and changes of the support particles size, on substrates mass transfer restrictions were studied on the alcoholysis of Camelina oil in the presence or not of t-butanol as co-solvent.
Significant changes of the support particle size were detected after their chemical modification. The particle size of Lewatit VP OC 1600 support of Novozym (R) 435 diminished in solvent-free systems. Alcoholysis rates in t-butanol media were enhanced caused by two favorable effects of this solvent: substrates dissolution and support swelling. This latter effect was not sufficient to promote protein desorption during processing. The hydrophobic environment created by 2,4,6-trinitrobenzensulfonic acid (TNBS) derivatization favoured the oil conversion. The TNBS derivative was also more stable than Novozym (R) 435 in methanolysis with solvent.
Scanning electron microscopy revealed that after 14 reaction cycles of 24h, a large proportion of biocatalyst particles were broken; however, matrix rupture did not cause biocatalysts inactivation. All modifications studied seemed to protect the support particles from breaking. Accumulated product particles on all biocatalysts surfaces did not impose significant mass transfer restrictions to substrates, but prevented protein desorption in urea solution. (C) 2016 Elsevier B.V. All rights reserved.