Effect of yeast extract supplementation on beta-galactosidase activity of Lactobacillus delbrueckii subsp. bulgaricus 11842 grown in whey.

摘要

Lactobacillus delbrueckii subsp. bulgaricus 11842 (LB 11842) was grown in reconstituted sweet whey supplemented with 0 to 1% yeast extract. The beta-galactosidase activity was determined from the hydrolysis of o-nitrophenyl-beta-D-galactopyranoside(ONPG) by sonicated cultures. Shake flask cultures containing 0.2-0.8% yeast extract gave 2.5 times higher beta-galactosidase activity than LB 11842 grown in sole (intact) whey. Supplementation with 1% yeast extract resulted in a three-fold increase of beta-galactosidase activity. The rate of acid production increased with the addition of yeast extract, whereas the increase in the total cell count with increasing amount of yeast extract was slight. A maximum beta-galactosidase activity of 1.08±0.15μmolONP released per minute per ml of culture was obtained using a whey based growth medium supplemented with 1% yeast extract.