Acidolysis and glyceride synthesis reactions using fatty acids with two Pseudomonas lipases having different substrate specificities

Nonthermal effect of microwave irradiation in nonaqueous enzymatic esterification

Microwave has nonthermal effects on enzymatic reactions, mainly caused by the polarities of the solvents and substrates. In this experiment, a model reaction with caprylic acid and butanol that was catalyzed by lipase from Mucor miehei in alkanes or arenes was employed to investigate the nonthermal effect in nonaqueous enzymatic esterification. With the comparison of the esterification carried by conventional heating and consecutive microwave irradiation, the positive nonthermal effect on the initial reaction rates was found substrate concentration-dependent and could be vanished ostensibly when the substrate concentration was over 2.0 mol L(-1). The polar parameter log P well correlates the solvent polarity with the microwave effect, comparing to dielectric constant and assayed solvatochromic solvent polarity parameters. The log P rule presented in conventional heating-enzymatic esterification still fits in the microwaved enzymatic esterification. Alkanes or arenes with higher log P provided positive nonthermal effect in the range of 2 ≤ log P ≤ 4, but yielded a dramatic decrement after log P = 4. Isomers of same log P with higher dielectric constant received stronger positive nonthermal effect. With lower substrate concentration, the total log P of the reaction mixture has no obvious functional relation with the microwave effect.

Fatty acid selectivity of lipases during acidolysis reaction between triolein and saturated fatty acids varying from caproic to behenic acids

The chain length selectivity of three immobilized lipases, namely, Lipozyme TL IM from Thermomyces lanoginosus, Lipozyme RM IM from Rhizomucor miehei, and Novozym 435 from Candida antarctica, was determined in acidolysis performed in hexane using the homologous series of even carbon number, saturated fatty acids (SFAs) of 6-22 carbons. Triolein with individual SFAs or a mixture of equimolar quantities of SFAs was used as the substrate. The effects of operating variables including the mole ratio of fatty acid to triolein, temperature, enzyme dosage, and time on incorporation were also investigated. Incorporation abilities of the enzymes tested were found to be significantly different for most of FAs at the experimental conditions evaluated. Lipases acted weakly on SFAs of which the carbon chain length was shorter than eight carbon atoms and higher than 18 carbon atoms. Lipases showed a bell-shaped distribution in incorporation vs chain length plot with a maximum around C12-C16. Among the experimental parameters tested, the effect of the substrate mole ratio was greater than those of the others, and the highest incorporation was observed for C12 (36.98%), C14 (37.63%), and C16 (38.66%) at a 4:1 substrate mole ratio with Lipozyme TL IM. Lipases caused significantly different levels of acyl migration from sn-1,3 to sn-2 positions.

Catalytic properties of mycelium-bound lipases from Aspergillus niger MYA 135

A constitutive level of a mycelium-bound lipolytic activity from Aspergillus niger MYA 135 was strongly increased by 97% in medium supplemented with 2% olive oil. The constitutive lipase showed an optimal activity in the pH range of 3.0-6.5, while the mycelium-bound lipase activity produced in the presence of olive oil had two pH optima at pH 4 and 7. Interestingly, both lipolytic sources were cold-active showing high catalytic activities in the temperature range of 4-8 degrees C. These mycelium-bound lipase activities were also very stable in reaction mixtures containing methanol and ethanol. In fact, the constitutive lipase maintained almost 100% of its activity after exposure by 1 h at 37 degrees C in ethanol. A simple methodology to evaluate suitable transesterification activities in organic solvents was also reported.