Magnetic Whole-Cell Biocatalyst Based on Intracellular Lipases of Candida catenulata as Promising Technology for Green Synthesis of Epoxy Fatty Acids

This study focuses on the development a green synthesis of epoxy fatty acids (EFAs) which are commonly used as the plasticizer in polymer industries. The intracellular lipases of Candida catenulata cells as a whole-cell biocatalyst (WCB) were examined in the bio-epoxidation of free fatty acids (FFAs) with hydrogen peroxide. The FFAs in soybean soap stock, an industrial by-product of vegetable oil factories, was used as the feedstock of the process. To remove phosphates from soap stock a degumming process was tested before the bio-epoxidation reaction and results revealed that the EFAs yield was improved using the degummed fatty acids (DFAs). The attachments of magnetic Fe3O4 nanoparticles to the surface of WCBs facilitated the recovery of the biocatalyst, and were improved stabilities. The activation energy for the magnetic whole-cell biocatalysts (MWCB) was 48.54kJmol-1, which was lower than the WCB system (51.28kJmol-1). The EFA yield was about 47.1% and 33.8% after 3h for the MWCBs and 2h for the WCBs, respectively. The MWCBs displayed acceptable reusability in the repetitious bio-epoxidation reaction with maintaining 59% of the original activity after 5 cycles whereas the performance of the WCBs was 5.9% at the same conditions. The effects of influential factors such as reaction time, molar ratio of H2O2 to C=C, and batch and semi-batch operations were investigated for both biocatalyst systems. The quality of EFAs was characterized by FTIR and GC-MS analyses.

Improving efficiency and reducing enzyme inactivation during lipase-mediated epoxidation of α-pinene in a double-phase reaction system

Chemoenzymatic epoxidation of olefin mediated by lipase is a green and environmentally friendly alternative process. However, the mass transfer barrier and lipase deactivation caused by the traditional organic-water biphasic reaction system have always been the focus of researchers' attention. To overcome these issues, we investigated the effects of reaction temperature and two important substrates (H₂O₂ and acyl donor) on the epoxidation reaction and interfacial mass transfer. As a result, we determined the optimal reaction conditions: a temperature of 30 °C, 30 wt-% H₂O₂ as the oxygen source, and 1 M lauric acid as the oxygen carrier. Additionally, by simulating the conditions of shaking flask reactions, we designed a batch reactor and added a metal mesh to effectively block the direct contact between high-concentration hydrogen peroxide and the enzyme. Under these optimal conditions, the epoxidation reaction was carried out for 5 h, and the product yield reached a maximum of 93.2%. Furthermore, after seven repetitive experiments, the lipase still maintained a relative activity of 51.2%.

Soft synthesis and characterization of goethite-based nanocomposites as promising cyclooctene oxidation catalysts

Goethite based nanocomposites with a different composition such as 6FeO(OH)·MnO(OH)·0.5H₂O (Mn-composite), xFeO(OH)·M(OH)₂·yH₂O (Co-composite (M: Co, x = 12, y = 3), Ni-composite (M: Ni, x = 7, y = 2)) and xFeO(OH)·MO·yH₂O (Cu-composite (M: Cu, x = 5.5, y = 3), Zn-composite (M: Zn, x = 6, y = 1.5)) have been prepared by a soft chemical synthesis consisting in acetate hydrolysis. The data provided by Fourier transform infrared (FTIR), ultraviolet-visible-near infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR) and Mössbauer spectra account for a slight modification of all composites' physicochemical properties compared to the starting material. Powder X-ray diffraction and transmission electron microscopy (TEM) investigations revealed the secondary phase nature and presence along with that of goethite. The TEM data are also consistent with a nano rod-like morphology with a 5–10 nm width and an average length of 40 nm. The catalytic oxidation of cyclooctene with O₂ using isobutyraldehyde as reductant and acetonitrile as a solvent was performed in batch conditions for 5 h at room temperature. The selectivity for the epoxide was higher than 99% for all tested solids. The conversion of cyclooctene decreased from 55% to 4% following the same order of variance as the base/acid sites ratio: Mn-composite > Fe-composite > Co-composite > Ni-composite > Zn-composite > Cu-composite. The 6FeO(OH)·MnO(OH)·0.5H₂O (Mn-composite) exhibited the most promising catalytic activity in cyclooctene oxidation, which can be correlated with the redox ability of Mn(iii) combined with the increased base character of this solid. The catalytic activity of this sample decreases by 10% after several successive reaction cycles.

Goethite based nanocomposites with different compositions (6FeO(OH)·MnO(OH)·0.5H₂O, xFeO(OH)·M(OH)₂·yH₂O or xFeO(OH)·MO·yH₂O where M = Co, Ni, Cu or Zn) have been prepared by a soft chemical synthesis via acetate hydrolysis.