Concerning about life quality promotes increasingly investigations into functional foods. Fructooligosaccharides (FOS), fructose oligomers, have applications in the food industry being used as nutraceutical ingredients and in products development with low sugar content. FOS are obtained by fermentation when the microorganisms are grown in medium with sucrose. The objective of this study was to evaluate the FOS production by submerged fermentation of Bacillus subtilis natto CCT7712 varying fermentation time at 12, 24, 36, 48, 60 and 72 hours in medium with sucrose at 400 g.L-1, pH 7.7, 234 rpm and 35 °C (conditions previously optimized); assays were performed in triplicate. After each time, FOS was quantified by high performance liquid chromatography, differential refractometric detector, carbohydrate column AMINEX HPX-87C (300 x 7.8 mm) at 80 °C, ultrapure water as mobile phase under a flow of 0.6 ml / min. The standards used were 1-kestose and nystose at 1 mg.mL-1. The results showed an increase in FOS production at 48 hours with maximum value of 175.12 g.L-1. However, higher productivity was observed at 24 hours of the procedure: 7.16 g.L-1.h-1 with production of 171.85 g.L-1. After 48 hours, was observed a reduction of 18% in production FOS with minimum of 145, 84 g.L-1 and 70% reduction in productivity with minimum value of 2.02 g.L-1.h-1. The results showed the influence of fermentation time on the productive performance of B. subtilis natto CCT7712, promising FOS producer.