Esterase and protease activities of Bacillus spp. from afitin, iru and sonru; three African locust bean (Parkia biglobosa) condiments from Benin
Fifty strains of Bacillus spp. comprising Bacillus subtilis and Bacillus licheniformis previously isolated from afitin, iru and sonru were examined for esterase and protease activities. The electrophoretic profiles of fermented African locust bean protein (ALBP), using strains presenting the highest protease activities in casein agar, were analyzed by SDS-PAGE to select strains with good ability to be used as starter cultures. All the Bacillus spp. tested showed esterase activity against tributyrin with high variability among strains. Strains showing the highest esterase activities were B. subtilis, primarily isolated from iru, sonru and lastly in afitin. Only 62% (31/50) of the Bacillus strains tested showed perceptible, but highly variable protease activity in casein agar. Bacillus strains showing the highest protease activities comprised strains of B. subtilis isolated from afitin and iru and strains of B. licheniformis isolated from iru and sonru. A B. subtilis strain isolated from afitin showed high esterase as well as high protease activity. The electrophoretic profile by SDS-PAGE of ALBP fermented by the Bacillus spp. having the highest protease activities showed degradation products with a wide range of molecular size between 4 and 250 kDa. Variability of the characteristics of the Bacillus spp. tested give new opportunities for their use as starter culture for products development.
Keywords: Bacillus subtilis, bacillus licheniformis, fermentation, esterase and protease activity, SDS-PAGE