Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Seven strains of the genus Kluyveromyces were screened for β-galactosidase activity in a synthetic medium. Kluyveromyces marxianus CCT 7082 was selected as the best enzyme producer for optimization of the culture medium. A fractional factorial design 2^(4-1) was used to determine the most relevant variables of the culture medium composition for the enzyme production. The parameters studied were the concentrations of lactose, yeast extract and (NH4)2SO4 as well as pH, and all were shown to have significant effects on the production of the enzyme. Based on the results from the first factorial design, lactose, yeast extract and (NH4)2SO4 concentrations were selected to be utilized in a 2³ central composite rotatable design (CCRD). This led to a further optimization of the fermentation conditions to achieve higher enzyme activities, which reached 10.6 U/mL.Ispitana je aktivnost β-galaktozidaze u sedam sojeva vrste Kluyveromyces u sintetskoj podlozi. Za optimiranje podloge odabran je soj Kluyveromyces marxianus CCT 7082 koji je proizveo najviše enzima. Pri određivanju najznačajnijih varijabla sastava podloge za proizvodnju enzima primijenjen je reducirani faktorski plan 2^(4-1). Istraženi su sljedeći parametri: koncentracija laktoze, kvaščeva ekstrakta i (NH4)2SO4 te pH-vrijednost, pa je utvrđeno da svi parametri značajno utječu na proizvodnju enzima. Prema rezultatima prvoga faktorskog plana, za izradu 2³ centralno složenog rotacijskog plana odabrani su koncentracija laktoze, kvaščeva ekstrakta i (NH4)2SO4. Daljnjim optimiranjem uvjeta fermentacije postignuta je veća aktivnost enzima, i to čak do 10,6 U/mL
