A novel and sensitive plate assay for screening of tannase-producing bacteria

In the present investigation, a new method for isolation and selective screening of tanninolytic, i.e. tannase-producing, bacteria was developed and compared with the earlier prevalent method. Tannase-producing bacteria were screened on agar plates using a newly developed plate assay method in which tannase cleaves the tannin–protein complex formed by addition of tannic acid to the medium, and forms a greenish brown zone around the bacterial colony due to the degradation of tannic acid. Using conventional methods, the zone formed was not clearly visible and pigmentation development took 3–4 days; however, the new method yielded clearer and more sensitive results within a shorter incubation time of 48–72 h.