Characterization of soil microbiota for the production of cyclodextrin glucanotransferase in northwestern Benin

The microorganisms of the soil microbiota, essential for soil fertility, remain underexplored in West Africa for their potential in industrial enzymes, particularly cyclodextrin glucanotransferase (CGTase). This study aims to characterize soil microorganisms capable of producing CGTase in the yam tuber-producing communes of Natitingou and Toucountouna. Thirty-five soil samples were collected from yam fields at depths of 10 cm and 50 cm. Physicochemical parameters pH, oxygen content, conductivity, total dissolved solids, and salinity were measured, microbial counts and identification were performed using standard bacteriological methods. Quantitative screening of isolated strains was carried out by incubating strains with commercial starch and potato broth for 48h, followed by enzymatic assay by spectrophotometry. At 10 cm depth, microbial loads ranged from 2.06×10¹¹±4.23×10⁹ CFU/g to 2.60×10¹¹±1.57×10¹⁰ CFU/g while at 50 cm, they varied from 2.11×10¹¹±2.10×10¹⁰ CFU/g to 3.00×10¹¹±3.47×10¹⁰ CFU/g. The isolated species included B. anthracis, B. brevis, B. cereus, B. licheniformis, B. subtilis, and B. pumilus CGTase activity ranged from 0.063±0.0524×10-3 U/ml (commercial starch) to 23±0.00694×10-3 U/ml, and from 16±0.0542×10-3 U/ml to 24±0.00694×10-3 U/ml (potato broth). B. cereus and B. subtilis exhibited the highest CGTase yields, particularly with potato broth. These findings highlight the potential of B. cereus and B. subtilis for microbial CGTase production.