Degradation of polysaccharides and non-digestible oligosaccharides by Bacillus subtilis and Bacillus pumilus isolated from Soumbala, a fermented African locust bean (Parkia biglobosa) food Condiment

In order to select starter cultures for controlled fermentation of African locust beans, Bacillus subtilis and B. pumilus from Soumbala were investigated for their ability to degrade arabinogalactan, stachyose, raffinose and sucrose--the main polysaccharides and oligosaccharides in African locust bean. The methods used were liquefaction of gels of galactomannan for screening, pH measurement and High Performance Anion Exhange Chromatography - Pulsed Amperometric Detection (HPAEC-PAD) for detailed degradation study of the carbohydrates. For B. subtilis isolates, liquefaction of galactomannan gels was observed and HPAEC-PAD showed that arabinogalactan and stachyose were partially degraded while raffinose was fully degraded after 48 h of fermentation. Melibiose, fructose and traces of galactose were detected as residual sugars. For B. pumilus isolates much weaker degradation of the carbohydrates was observed. Two isolates of B. subtilis showed strong ability to degrade the oligosaccharides and they are seen as promising starter cultures for fermentation of African locust bean.