A recirculating spiral reactor (RSR) was designed for polystyrene nanofibers immobilized beta-galactosidase (PSNF-Gal) assembly for galacto-oligosaccharides (GOS) production from lactose. GOS selectivity using, the PSNF-Gal assembly exceeded 1.5 to 3.7-folds. The maximum lactose conversion rate was 42 g of lactose/L/h and the GOS productivity rate was 23 g/L/h in 6 h. An increase in the feeding flow rate resulted in enhancing lactose conversion and GOS production but beyond 15 mL/min led to a significant decrease in GOS production and enzyme leaching. An increase in the initial lactose concentration from 300 to 700 g/L was found to enhance GOS yield around 1.7 times, while reducing lactose conversion about 1.6 times. The best GOS yield was determined to be 159 g/L with 86% lactose conversion in 24 h using 400 g/L lactose at 15 mL/min feeding rate. Our results demonstrate that the recirculating spiral reactor could be scaled up for bioconversion process using immobilized enzymes.