determination of proper conditions for the production of crude beta-galactosidase using lactobacillus delbrueckii ssp. bulgaricus

proper conditions for producing crude beta-galactosidase from waste materials were de-termined. this enzyme is to be used in the production of lactose-hydrolyzed milk. whey permeate was used as a basic medium. twenty seven treatments were developed by 3 vary-ing factors of: yeast extract (1, 2, and 3 %), wheat steep liquor (1, 2, and 3 %), and whey powder (0.5, 1, and 1.5 %). crude enzyme extract was obtained by sonication of the cells collected from cultivation of lactobacillus delbrueckii ssp. bulgaricus in various media at 43oc. the beta-galactosidase activity was assessed using ortho-nitro-phenyl-beta-d-galactopyranoside (onpg). yeast extract and whey powder had both significant effects (p< 0.01), while wheat steep liquor proved to be ineffective. yeast extract had the most pro-nounced effect on the production of beta-galactosidase. the effect of the interactions of yeast extract-whey powder and wheat steep liquor-whey powder were significant at 5 % level (p< 0.05), while the effect of the interaction of yeast extract-wheat steep liquor was sig-nificant at 1% level (p< 0.01). interaction effect of the 3 factors on the production of beta-galactosidae was significant (p< 0.01). the best combination for production of beta-galactosidase (4.924 u ml-1) was 3% yeast extract, 1.5% whey powder and 2% wheat steep liquor.