RESUMEN
Oleaginous yeast Trichosporon fermentans was proved to be able to use sulphuric acid-treated sugar cane bagasse hydrolysate as substrate to grow and accumulate lipid. Activated charcoal was shown as effective as the more expensive resin Amberlite XAD-4 for removing the inhibitors from the hydrolysate. To further improve the lipid production, response surface methodology (RSM) was used and a 3-level 4-factor Box-Behnken design was adopted to evaluate the effects of C/N ratio, inoculum concentration, initial pH and fermentation time on the cell growth and lipid accumulation of T. fermentans. Under the optimum conditions (C/N ratio 165, inoculum concentration 11%, initial pH 7.6 and fermentation time 9 days), a lipid concentration of 15.8g/L, which is quite close to the predicted value of 15.6g/L, could be achieved after cultivation of T. fermentans at 25°C on the pretreated bagasse hydrolysate and the corresponding lipid coefficient (lipid yield per mass of sugar, %) was 14.2. These represent a 32.8% improvement in the lipid concentration and a 21.4% increase in the lipid coefficient compared with the original values before optimization (11.9g/L and 11.7). This work further demonstrates that T. fermentans is a promising strain for lipid production and thus biodiesel preparation from abundant and inexpensive lignocellulosic materials.
Asunto(s)
Biocombustibles , Celulosa/farmacología , Lípidos , Trichosporon/crecimiento & desarrollo , Celulosa/química , Carbón Orgánico/química , Concentración de Iones de Hidrógeno , Hidrólisis/efectos de los fármacos , Lípidos/biosíntesis , Lípidos/química , Lípidos/aislamiento & purificación , Poliestirenos/química , Polivinilos/química , Trichosporon/metabolismoRESUMEN
Immobilized lipase from Penicillium expansum, a novel and inexpensive enzyme preparation that we immobilized in our laboratory, was an excellent catalyst for highly regioselective acylation of arbutin with fatty acid vinyl esters. For the enzymatic butanoylation of arbutin, under the optimal conditions, initial reaction rate was 75.1 mM/h, and substrate conversion and regioselectivity were greater than 99%. In addition, a variety of 6'-esters of arbutin were prepared with high conversion (>99%) and excellent regioselectivity (>99%). It was found that the enzymatic reaction rate varied widely with different acyl donors, presumably owing to their different interactions with the active site of the lipase. The immobilized lipase from P. expansum displayed highest catalytic activity with medium-length straight-chain acyl donors. Acyl donors bearing a substituent or a conjugate double bond gave reduced reaction rates.
Asunto(s)
Arbutina/síntesis química , Ácidos Grasos/química , Lipasa/química , Penicillium/clasificación , Penicillium/enzimología , Acilación , Activación Enzimática , Estabilidad de Enzimas , Enzimas Inmovilizadas/química , Esterificación , Oxidación-Reducción , Especificidad de la EspecieRESUMEN
The biocatalytic enantioselective reduction of 4'-methoxyacetophenone to (S)-1-(4-methoxyphenyl)ethanol was successfully conducted in a hydrophilic IL-containing co-solvent system using immobilized Rhodotorula sp. AS2.2241 cells. Of all the tested ILs, the best results were observed with the novel IL 1-(2'-hydroxy)ethyl-3-methylimidazolium nitrate (C(2)OHMIM.NO(3)), which showed a good biocompatibility with the cells and increased the cell membrane permeability moderately, thus improving the efficiency of the bioreduction. To better understand the bioreduction, several crucial influential variables were also examined. The optimal C(2)OHMIM.NO(3) content, buffer pH, reaction temperature and substrate concentration were 5.0% (v/v), 8.5, 25 degrees C and 12 mM, respectively. Under the optimized conditions, the initial reaction rate, the maximum yield and the product e.e. were 9.8 micromol/hg(cell), 98.3% and >99%, respectively, which are much better than the results previously reported. The established biocatalytic system has proven to be highly effective for the reduction of other aryl ketones. Also, the cells exhibited excellent operational stability in the presence of C(2)OHMIM.NO(3). Moreover, the ILs can accumulate within the cells, suggesting that ILs are likely to interact with the related enzymes within the cells.