The lipases CAL-B, PSL, PSL-C, PSL-D, and A. niger lipase, free or immobilized in starch (obtained from two types of yam, known in Brazil as “cará” (Discorea alata L.) and “inhame” (Colocasia esculenta (L.) Schott) or gelatin films, were used in the acylation of (RS)-sec-butylamine with different acyl donors in various organic solvents applying conventional heating (CH) or microwave (MW) irradiation. In the case of free A. niger lipase, the conversion degrees were three times higher using MW irradiation when compared to conventional heating at 35 ºC. Using free A. niger lipase, the (R)-amide was obtained with a conversion degree of 21%, resulting in ee p > 99% and E-value (enantioselectivity value) > 200, in 1 min of reaction under MW irradiation. When the A. niger lipase was immobilized in yam starch films, the (R)-amide was obtained in moderate conversions of 8-25% after 3 or 5 min of reaction under MW irradiation, but with higher selectivity (ee p > 99% and E > 200) in comparison with the free form (conversion degree of 45%, ee p 81% and E value of 18).
enzymatic resolution; lipase; immobilization; microwave irradiation
