Among a number of yeast strains screened for whole cell transgalactosylating activity, Kluyveromyces marxianus NCIM 3551 was found to be most suitable biocatalyst for production of galacto-oligosaccharides (GOS). Cell permeabilization lead to an efficient bioconversion by β-galactosidase resulting in synthesis of GOS. A maximum GOS yield of 36% (w/w) of total sugars was achieved and the products consisted of tri- and tetra-galacto-oligosaccharides. A lactose conversion rate of 80% and productivity of 24g/L/h was obtained under the optimum conditions at lactose concentration of 20% (w/v), temperature 40°C, pH 6.5 and enzyme units after 3h of reaction time. Tetrasaccharides were the main component of the reaction mixture. The products were quantitated by HPLC and structurally characterized by mass spectrometry.
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