Transgalactosylation of lactose for synthesis of galacto-oligosaccharides using Kluyveromyces marxianus NCIM 3551

•Synthesis of galacto-oligosaccharides (GOS) using permeabilized whole cells of Kluyveromyces marxianus NCIM 3551.•High yield of GOS with low substrate concentration.•Higher productivity due to shorter reaction time.•Galacto-tetraose as the main reaction product.

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 24 g/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 3 h of reaction time. Tetrasaccharides were the main component of the reaction mixture. The products were quantitated by HPLC and structurally characterized by mass spectrometry.