ASL, a natural immobilized lipase found in Araujia sericifera latex

DI SANTO MEZTLER, P.; FAIT, M.E.; FORESTI, M.L.; MORCELLE, S.R.

Workshop; VII workshop on biocatalysis and biotransformations-1º simposio latinoamericano de biocatálisis y biotransformaciones; 2014

Hydrolytic activity of ASL toward a natural substrate (cottonseed oil) and synthetic ones (short chain p-nitrophenyl alkanoates) was proved. In the hydrolysis of cottonseed oil ASL optimum pH was comprised in the range of 8.0-9.0 (nominal conversion of cottonseed oil to oleic acid of 27%) and highest activity values were recorded in the 50-70°C interval (nominal conversions to oleic acid of 33-35%). In the standard reaction conditions (40ºC, pH 8.5, 2 min reaction, 5 mg of biocatalyst), Novozyme 435 showed no activity. When p-nitrophenyl esters (butyrate, dodecanoate and palmitate) were used as substrates for ASL activity, highest specificity towards the smallest alkanoate (butyrate) was found. In the standard conditions (pH 8.0, Tris-HCl 0.05 M, Triton X-100 0.0075% v/v, 2.5 mg of biocatalyst, 37°C), the activity of ASL was much lower than that exhibited by Novozyme 435 (0.0028 IU/mg for ASL versus 1.61 IU/mg for the commercial biocatalyst). ASL was also tested in the esterification of different carboxylic acids (butyric, caproic and lauric acids) with n-butanol using n-heptane or n-hexane as solvents. In both solvents assayed, ASL showed higher affinity for butyric and lauric acid, whereas esterification of caproic acid was less favored. In reference to the effect of the solvent used, the activity of ASL was found to be higher in n-heptane than in n-hexane. The effect of temperature on the esterification reaction in the different media was also tested. In n-hexane, in the range assayed (25-50ºC) lauric acid conversion continuously increased with temperature. Butyric acid esterification exhibited an optimum at 40ºC. When n-heptane was tested as solvent, lauric acid conversion was similar to the one found in n-hexane, but conversion rates at higher temperatures (60-70ºC) evidenced a reduction of lipase activity. In the case of butyric acid esterification, conversion showed an optimum in the 50-60ºC range. The synthetic activity of ASL was compared with that shown by Novozym 435 (40ºC, 1 h, 10 mg of biocatalyst). In the esterification of butyric acid with butanol a conversion of 93±4 % was observed for Novozyme 435, whereas for ASL the conversion was 33±2%. Esterification of lauric acid with butanol by Novozym 435 achieved a conversion of 89±5%, whereas for ASL the conversion was 33±2%.