Catalytic Properties of Lipase Extracts from Aspergillus niger

Abstract

Ispitivanjem lipolitičkih sojeva metodom uzgoja na podlozi s dodatkom rodamina B i maslinova ulja odabran je soj plijesni Aspergillus niger MYA 135. Proizvodnja lipaze submerznim postupkom u podlozi s dodatkom 2 % maslinova ulja poboljšana je za više od 50 % s obzirom na osnovne uvjete uzgoja. Optimalni katalitički uvjeti za proizvodnju lipaze uz dodatak maslinova ulja bili su pH=6,5 i temperatura od 30 do 35 °C. Pri proizvodnji ekstrakta lipaze u osnovnim uvjetima te su se vrijednosti približavale kiselom mediju (4,5 i 6,5) i temperaturi od 35 do 37 °C. Uočena je neznatna promjena aktivnosti lipaze s promjenom pH vrijednosti. Predinkubacijom pri 37 ili 40 °C povećana je aktivnost lipaze potpomognuta dodatkom maslinova ulja. No, uzgojem u osnovnom mediju pri rasponu od 30 do 55 °C ta je aktivnost smanjena. Aktivnost lipolitičkih ekstrakata neznatno se smanjila dodatkom 50 % organskih otapala koja se miješaju s vodom, dok su alifatska otapala što se ne miješaju s vodom smanjila aktivnost lipaze za 20-80 %.Screening of lipolytic strains using Rhodamine-B/olive oil plate technique allowed the selection of Aspergillus niger MYA 135. Lipase production in submerged culture containing 2 % olive oil was enhanced by more than 50 % compared to basal cultural conditions. Optimal catalytic conditions for olive oil-induced lipase were pH=6.5 and 30–35 °C. These values were shifted to the acid region (4.0–6.5) and 35–37 °C when lipase extract was produced under basal conditions. Slight changes of the residual lipase activity against the pH were found. However, preincubation at either 37 or 40 °C caused an increase in the olive oil-inducible lipolytic activity. On the contrary, lipase residual activity decreases in the 30–55 °C range when it was produced in basal medium. Lipolytic extracts were almost not deactivated in presence of 50 % water-miscible organic solvents. However, water-immiscible aliphatic solvents reduced the lipase activity between 20 and 80 %