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In this work, phytosterol ester was synthesized using Yarrowia lipolytica lipase Ylip2 that had been immobilized on inorganic support in a solvent-free system and reacted in a computer-aided water activity controlled bioreactor. The immobilization of Ylip2 on celite led to a remarkable increase in the phytosterol conversion compared to that of free lipase. An investigation of the reaction conditions were oleic acid as the fatty acid variety, 10,000 U/g substrate, and a temperature of 50 °C for phytosterol ester synthesis. Controlling of the water activity at a set point was accomplished by the introduction of dry air through the reaction medium at a digital feedback controlled flow rate. For the esterification of phytosterol ester, a low (15%) water activity resulted in a considerable improvement in phytosterol conversion (91.1%) as well as a decreased reaction time (78 h). Furthermore, Ylip2 lipase immobilized on celite retained 90% esterification activity for the synthesis of phytosterol oleate after reused 8 cycles, while free lipase was only viable for 5 batches with 90% esterification activity remained. Finally, the phytosterol oleate space time yield increased from 1.65 g/L/h with free lipase to 2.53 g/L/h with immobilized lipase. These results illustrate that the immobilized Yarrowia lipolytica lipase Ylip2 in a water activity controlled reactor has great potential for the application in phytosterol esters synthesis. [ABSTRACT FROM AUTHOR]

We have developed an improved and effective method to immobilize Yarrowia lipolytica lipase Lip2 (YLIP2) on an epoxy poly-(glycidylmethacrylate-triallyisocyanurate-ethyleneglycoldimethacrylate) (P GMA-TAIC-EGDMA ) support structure with or without amine or/and protein modifications. Our results show that there is an increase in the activity of the immobilized lipase on n-butylamine (BA) modified support (420 U/g support) and the biocompatible gelatin modified support (600 U/g support) when compared to the support without modification (240 U/g support). To further study the influences of BA and gelatin modification on the activity of the immobilized lipase, gelatin and BA were concurrently used to decorate the support structure. Lipase immobilized on 2% BA/gelatin (1:1) modified support obtained the highest activity (1180 U/g support), which was five-fold higher than that on a native support structure. These results suggest that the activity of a support-immobilized lipase depends on the support surface properties and a moderate support surface micro-environment was crucial for elevated activity. Collectively, these data show that a combined gelatin and BA modification regulates the support surface more suitable for immobilizing YLIP2. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lipase was absorbed on surface hydrophobic modified silk fibers. [•] Immobilized lipase and feeding methods improve synthesis of tri-TMP esters. [•] Immobilized lipas showed increase esterification activity and decrease hydrolysis activity. [•] TMP-feeding methods kept a high molar ratio of fatty acid to TMP during process. [Copyright &y& Elsevier]

Methanol is regularly used as a substratefor biodiesel synthesis.Excess methanol can however inhibit the lipase activity. In the presentwork, the activity and conformational changes of Yarrowialipolyticalipase (LIP2) at different concentrationsof methanol were investigated by measuring fluorescence, UV–visspectra, and molecular dynamics simulations. The lipase tended toexpand at higher concentrations of methanol, and the methanol moleculeswere able to enter into the LIP2, leading to microenvironment changesaround the aromatic amino acids. More hydrophobic groups were exposedto the solvents at high methanol concentrations, and the originalhydrophobic interaction in the protein was destroyed, thus resultingin the tertiary structure change of the lipase. [ABSTRACT FROM AUTHOR]