tannic acid degradation by klebsiella strains isolated from goat feces

background and objectives: tannins are toxic polyphenols that either bind and precipitate or condense proteins. the high tannin content of some plants is the preliminary limitation of using them as a ruminant feed. so, the aim of this study was the isolation and characterization of tannic acid degrading bacterial strains from goat feces before and after feeding on pis- tachio-soft hulls as tannin rich diet (trd). materials and methods: bacterial strains capable of utilizing tannic acid as sole carbon and energy source were isolated and characterized from goat feces before and after feeding on trd. tannase activity, maximum tolerable concentration and biodegradation potential were assessed. results: four tannase positive isolates were identified as klebsiella pneumoniae. isolated strains showed the maximum tolerable concentration of 64g/l of tannin. the tannic acid degradation percentage at a concentration of 15.0 g/l reached a maximum of 68% after 24 h incubation, and more than 98% after 72 h incubation. the ph of the medium also decreased along with tannic acid utilization. conclusions: it is obvious that trd induced adaptive responses. thus, while the bacteria were able to degrade and detoxify the tannic acids, they had to adapt in the presence of high concentrations of tannic acid. so, these isolates have an amazing potential for application in bioremediation, waste water treatment, also reduction of tannins antinutritional effects in animal feeds.