ASPERGILLUS-NIGER LIPASES - INDUCTION, ISOLATION AND CHARACTERIZATIONOF 2 LIPASES FROM A MZKI A116 STRAIN

Aspergillus niger strain MZKI A116 was used to produce lipolytic enzym es in submerged culture. Lipase production was induced by addition of olive oil to a complex medium with an initial pH of 5.0. Maximal activ ity was reached after 70 h in a 15 1 bioreactor at 30 degrees C with a eration of 0.5 vvm and agitation 400 rpm. Optimal temperature and pH c onditions for the action of the lipases tested on tributyrin were 45 d egrees C and pH 7.0. Triacetin and tributyrin were shown to be the bes t substrates. The presence of iron and silver ions at low concentratio ns did not alter the activities. Two enzymes possessing lipase activit y were isolated by acetone precipitation followed by ion-exchange chro matography. The molecular weights were 43 kDa and 65 kDa with isoelect ric points of pH 4.1 and 4.2, respectively. The higher molecular weigh t lipase showed preference toward 1- and 3-positions of the triglyceri de molecule and was stereoselective for the sn-l position with an enan tiomeric excess of 20%. It displayed strong activity toward naphthyl, indolyl, umbelliferyl and resorufin esters and was active on esters of hydroxynaphthoic acid anilide, while it showed no activity toward est ers of hydroxypyrene trisulfonic acid.