An Enzymatic–Colorimetric Assay for the Quantification of <i>Bifidobacterium</i>

Abstract

An enzymatic-colorimetric assay for the quantification of <i>Bifidobacterium</i> was developed. The method, based upon the standard detection of fructose-6-phosphate phosphoketolase activity, was optimized with respect to bacterial cell pretreatment, time of incubation, and substrate concentration. The relationship between bacterial biomass and phosphoketolase activity was linear in a wide spectrum of bacterial densities. Higher sensitivity over the standard method was achieved by using 0.25% Triton X-100 in the reaction mixture to pretreat the bacterial cells. Because autoaggregation is a frequent feature among <i>Bifidobacterium</i> strains, this simple and reproducible method offers good advantage over viable plate count and turbidimetric techniques. The methodology can also be applied to the assessment of adherent <i>Bifidobacterium</i> strains to human epithelial cells.