Immobilization of CALB on activated chitosan: Application to enzymatic synthesis in supercritical and near-critical carbon dioxide.

The objective of this new paper was to evaluate the enzymatic esterification reaction conducted in supercritical or near-critical CO2, catalyzed by immobilized lipase B from Candida antarctica (CALB). The biocatalyst was prepared through the immobilization of CALB by covalent attachment using chitosan sequentially activated with Glycidol, ethylenediamine (EDA) and glutaraldehyde as support. In order to determine the best operational conditions of the esterification reaction (1: 1 (alcohol-acid); biocatalyst content, 10% (by substrate mass); 45 °C), an experimental design (23) was conducted to evaluate the effects of the following parameters: alcohol to oil molar ratios, reaction time and temperature. The maximum loading of chitosan was 20 mg protein/g support, and the thermal and solvent stability of the new biocatalyst was higher than that of the CALB-GX (by a 26-fold factor), CALB-OC (by a 53-fold factor) and Novozym 435 (by a 3-fold factor). The maximum conversion was 46.9% at a temperature of 29.9 °C, ethanol to oleic acid molar ratio equal to 4.50:1, and a reaction time of 6.5 h. Additionally, the removal of water from the medium, by using molecular sieves, promoted a 16.0% increase in the conversion of oleic acid into ethyl esters.

Extraction of lipids from microalgae by ultrasound application: prospection of the optimal extraction method.

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20-50% of dry weight) of lipids. A successful and economically viable algae based oil industry will depend on the selection of appropriate microalgal strains and the selection of the most suitable lipid extraction method. In this paper, five extraction methods were evaluated regarding the extraction of lipids from Chlorella vulgaris: Bligh and Dyer, Chen, Folch, Hara and Radin, and Soxhlet. Furthermore, the addition of silica powder was studied to evaluate the introduction of more shear stress to the system as to increase the disruption of cell walls. Among the studied methods, the Bligh and Dyer method assisted by ultrasound resulted in the highest extraction of oil from C. vulgaris (52.5% w/w). Addition of powder silica did not improve the extraction of oil.

Bioprospecting for oil producing microalgal strains: evaluation of oil and biomass production for ten microalgal strains.

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20-50% of dry weight) of lipids. A successful and economically viable algae based oil industry depends on the selection of appropriate algal strains. In this study ten species of microalgae were prospected to determine their suitability for oil production: Chaetoceros gracilis, Chaetoceros mulleri, Chlorella vulgaris, Dunaliella sp., Isochrysis sp., Nannochloropsis oculata, Tetraselmis sp., Tetraselmis chui, Tetraselmis tetrathele and Thalassiosira weissflogii. The study was carried out in 3 L glass flasks subjected to constant aeration and controlled artificial illumination and temperature at two different salinities. After harvesting, the extraction of oil was carried out using the Bligh and Dyer method assisted by ultrasound. Results showed that C. gracilis presented the highest oil content and that C. vulgaris presented the highest oil production.