Optimization of galacto-oligosaccharide production by Bifidobacterium infantis RW-8120 using response surface methodology

Oligosaccharide (OS) production, cell concentration (2 x 10(9) colony-forming unit/ml), lactose concentration (25% wt/vol), reaction time (6 h), and temperature (50 degrees C) were chosen as the central condition of the central composite design (CCD) for optimizing the production process using Bifidobacterium infantis RW-8120 in skim milk. Statistical analysis (P<0.01) revealed that the most relevant variable concerning OS production and yield was the lactose concentration. The coefficient of determination (R(2)) is good for the second-order OS production model (0.92) and fairly good for the second-order nonlinear OS yield model (0.816). An increase of lactose concentration and temperature resulted in a higher OS production. The optimal values for OS production appear to be near the area associated with the central points of the modeling design except for the lactose concentration, which was 40% (wt/vol) of the final volume.