CONICET | Buscador de Institutos y Recursos Humanos

Lipases are an important group of biocatalysts that act in the hydrolysis of triglycerides releasing fatty acids and glycerol. The importance and application of lipases in synthesis reactions has increased dramatically over the last decade and they have become a great alternative for the modification of fats and oils in the oleochemical industry. Lipases have been purified and characterized from various sources (animal, microbial and plant), being microbial lipases the most studied ones. However, there is an increasing interest in plant lipases since they appear to be economical and versatile. With this in mind and based on the progress already reported in bibliography, we have begun to study lipase activity in castor bean powders treated with acetone. Reaction medium used contained 5 mL of acetate buffer (pH 4.4) and 5 ml of an emulsion of high oleic sunflower oil (substrate) and water. The first experimental design aimed at analyzing the effect of three parameters (concentration of surfactant = 0-2.5%, oil = 16 to 12% and lipase powder = 0.05-0.15 g) on the response variable R, lipase activity (mmol FFA/ g lipase powder ? g Oil ? h, FFA: free fatty acids). Results showed an increase of R by using high concentrations of oil and low concentrations of enzyme and surfactant. The R maximum obtained was 22,2 mmol FFA / g lipase powder ? g Oil ? h using the lowest lipase concentration and the highest oil concentration in the absence of surfactant. Since no local maximum was found within the studied area, it was decided to conduct a second experimental design. The aim of this work is to evaluate R behavior in an expanded area and the possible existence of a local maximum. A factorial design with 3 levels and a total of 24 experiments with 4 replicates at the central point was used. The chosen parameters and their respective ranges were: A, amount of oil (0.5-1 g oil / g water in emulsion) and B, amount of enzyme (0.005 to 0.05 g). The reaction temperature was 37 ° C, the reaction time 1.5 h, and no surfactant was used.FFA used in R calculation were determined by GC after solvent extraction of the by-products. Results were analyzed using Design-Expert 7.0.0 software. Although the response surface adjusted well to numerical data (lack of fit was not significant), the quadratic model obtained was not significant (p = 0.17). This means that although the activities obtained were greater than or equal to the point of maximum activity of the previous experimental design, differences between them could not be found within the studied area. At the same time, this means that the enzyme can operate efficiently within these parameter?s ranges.