Carlos Eduardo Barão

Characterization of Biocatalysts Prepared with Thermomyces lanuginosus Lipase and Different Silica Precursors, Dried using Aerogel and Xerogel Techniques

The use of lipases in industrial processes can result in products with high levels of purity and at the same time reduce pollutant generation and improve both selectivity and yields. In this work, lipase from Thermomyces lanuginosus was immobilized using two different techniques. The first involves the hydrolysis/polycondensation of a silica precursor (tetramethoxysilane (TMOS)) at neutral pH and ambient temperature, and the second one uses tetraethoxysilane (TEOS) as the silica precursor, involving the hydrolysis and polycondensation of the alkoxide in appropriate solvents. After immobilization, the enzymatic preparations were dried using the aerogel and xerogel techniques and then characterized in terms of their hydrolytic activities using a titrimetric method with olive oil and by the formation of 2-phenylethyl acetate in a transesterification reaction. The morphological properties of the materials were characterized using scanning electron microscopy, measurements of the surface area and pore size and volume, thermogravimetric analysis, and exploratory differential calorimetry. The results of the work indicate that the use of different silica precursors (TEOS or TMOS) and different drying techniques (aerogel or xerogel) can significantly affect the properties of the resulting biocatalyst. Drying with supercritical CO2 provided higher enzymatic activities and pore sizes and was therefore preferable to drying, using the xerogel technique. Thermogravimetric analysis and differential scanning calorimetry analyses revealed differences in behavior between the two biocatalyst preparations due to the compounds present.

Influence of alcohol: oil molar ratio on the production of ethyl esters by enzymatic transesterification of canola oil

The influence of alcohol:oil molar ratio on the canola oil transesterification reaction in solvent-free medium using free lipase from Thermomyces lanuginosus and Burkholderia cepacia was studied. The experiments conducted in batch reactor for 72 h at 37°C in cosolvent-free reaction system with ethanol addition in three steps showed great potential for ester production. The stepwise addition of ethanol allowed increasing yield throughout the total period of the reaction, even if the course has limited reaction at times, minimizing possible deleterious effects of the alcohol on the enzyme structure. The highest yields were achieved with lipase from T. lanuginosus , despite presenting lower activity values than those of Burkholderia cepacia lipase, which proved to be less selective for ester production. In the reaction medium containing lipase from T. lanuginosus , 100 % yield was obtained using a molar ratio of 12:1. For B. cepacia lipase, the highest yield was 90.73% at a molar ratio of 6:1. In all cases studied, at least 92% of the triacylglycerols from canola oil were consumed. Keywords: Free lipase, Thermomyces lanuginosus, Burkholderia cepacia, molar ratio, solvent-free medium, transesterification reaction, triacylglycerols, diacylglycerols, monoacylglycerols, ester. Afr. J. Biotechnol Vol. 12 No. 50

Cereal bar with cassava bagasse: chemical composition and sensory acceptance

Cassava bagasse, regarded as an agricultural residue can be used as raw material in the development of new products. Cereal bars are foods that have increasingly gained consumers because of the practical use. The objective of this study was to evaluate the effect of adding cassava bagasse (0, 8 and 25%) on the chemical composition and sensory acceptance of coconut cereal bars with Brazil nuts. Cereal bars with cassava bagasse had higher moisture, protein and carbohydrates (fiber) contents than cereal bars without bagasse, lower ash contents and similar fat content. The addition of cassava bagasse caused a decrease in the acceptance of the cereal bars only in the concentration of 25%, however, the products had hedonic values greater than 7 in a 9-point hedonic scale and acceptability indices higher than 80%, indicating that consumers moderately liked them. It can be concluded that the use of up to 25% cassava bagasse in the cereal bar formulation yields products with improved nutritional value and appropriated consumer acceptance. The addition of cassava bagasse to food products is a good alternative in the use of this byproduct, due to the sensory characteristics of the obtained products and the reduction of production costs, because the cassava bagasse has low cost and increases the production yield.