Whey valorization using transgalactosylation activity of β-galactosidase

Abstract

Whey is the most significant by-product from the dairy industry that can cause serious environmental pollution problems. Namely, one of the main whey constituents is lactose, which is responsible for high biological oxygen demand (BOD) and chemical oxygen demand (COD) values. Hence, owing to the abundant amount of lactose in whey, removal or conversion of lactose proved to be the promising approach for the whey valorization. Hereby, we investigated a possibility of lactose bioconversion into wide range of valuable prebiotic compounds named galacto-oligosaccharides (GOS) using transgalactosylation activity of commercial β-galactosidase from Aspergillus orzyae. Obtained results showed that an ussual substrate for the GOS synthesis - lactose could be successfully replaced by much cheaper substrate - whey powder, since the quite similar composition of products (tri- and tetra- saccharides with dominant β-1,4 and β-1,6 linkages), as well as equal product yields have been achieved using both substrates. Therefore, in terms of yielding the high GOS yields, thorough optimization of the most important process parameters (enzyme concentration, temperature, pH, whey solution concentration and time) was performed. Finally, the highest obtained GOS concentration (60 g/l) was achieved using 40 % (w/v) whey solution (the highest examined concentration due to the low whey solubility) under the optimized conditions (50 C, pH 4.5) after 10h. Therefore, the findings of this study could provide a valuable contribution to the efficient and cost effective production of physiologically active GOS, and simultaneously solve the considerable problem of whey utilization and its appropriate disposal.