Valorization of whey via succession of concentration and bioconversion to galactooligosaccharide: a comparative study of feed effect on osmotic membrane distillation performance

This study explores the valorization of whey, a significant byproduct of dairy processing, through the integration of a batch reactor (R-Batch) with osmotic membrane distillation (OMD) for galactooligosaccharide (GOS) production. Whey streams, including acid whey, sweet whey, and ideal whey, were evaluated for their effects on GOS yield and membrane performance. By concentrating whey to favorable lactose levels using OMD, the integrated system (R-Batch + OMD) enhanced transgalactosylation activity while minimizing the hydrolysis rate. The R-Batch + OMD system significantly increased GOS yield, with ideal whey achieving the highest yield at 156 g L-1, representing a 22 % increase compared to microfiltered acid whey (121 g L-1) and sweet whey (93 g L-1). Additionally, ideal whey produced the highest tri-saccharides (GOS-3) content as 110 g L-1. The R-Batch + OMD also achieved higher lactose conversion rate for ultrafiltered ideal whey (52 %), outperforming microfiltered and ultrafiltered whey substrates. Furthermore, the long-chain GOS produced from ultrafiltered whey demonstrated the strongest prebiotic activity, comparable to the commercial product. These findings demonstrate the effectiveness of OMD in optimizing GOS production and highlight ideal whey as a superior substrate, both in terms of GOS yield and prebiotic benefits. Moreover, this research provides insights into optimizing membrane-based enzymatic synthesis systems for whey valorization.