Biotechnological process for producing black bean slurry without stachyose

Beans are important sources of proteins and other nutrients. However, stachyose and other oligosaccharides (RFOs) are present in this legume causing flatulence (H₂, CO₂ and CH₄), abdominal pain, and diarrhea. The problematic digestibility of these sugars in the small intestine is attributed to a lack of α-galactosidase, which is essential for the hydrolysis of α-1,6 linkages. The aim of the present work was to reduce the stachyose of black bean slurry by lactic acid fermentation using a selected Lactobacillus LPB56, an α-galactosidase producer. The bean slurry (6L) was fermented in a bioreactor with 1.3% (w/v) of CaCO₃, at 37 °C and 160 rpm. Bacterial cells increased from 2.4 × 10⁷ to 7.0 × 10⁸ CFU/mL, and the stachyose and other sugars were totally consumed after 18 h of fermentation. The maximum activity of α-galactosidase was 0.162 U/mL after 6 h. The fermentative process did not cause significant changes on the composition of the bean product.