Selection of strain, culture conditions and extraction procedures for optimum production of beta-galactosidase from Kluyveromyces fragilis.

Among 47 tested yeast strains, belonging to different genera, only two cultures of Kluyveromyces fragilis and Fabospora fragilis showed beta-galactosidase activity in shaken flasks. Three types of extraction were used to release the enzyme from K. fragilis cells: solvent and detergent extraction, freezing and thawing extraction, and mechanical disintegration prior to extraction, using Triton X-100. The results indicate that the highest yield could be obtained by mechanical disintegration of cells. Factors affecting the enzyme production were studied using fermentation media of different chemical composition. The medium containing lactose, salts and yeast extract with initial pH 7.0 was selected as the best for enzyme production. Monobasic ammonium phosphate (2.0 g/dm3) was found to be the best inorganic nitrogen source for enzyme production. The effect of phosphorus level was also studied.