Microbial degradation of tannins - A current perspective

Tannins are water-soluble polyphenolic compounds having wide prevalence in plants. Hydrolysable and condensed tannins are the two major classes of tan nins. These compounds have a range of effects on various organisms from tox ic effects on animals to growth inhibition of microorganisms. Some microbes are, however, resistant to tannins, and have developed various mechanisms and pathways for tannin degradation in their natural milieu. The microbial degradation of condensed tannins is, however, less than hydrolysable tannin s in both aerobic and anaerobic environments. A number of microbes have als o been isolated from the gastrointestinal tract of animals, which have the ability to break tannin-protein complexes and degrade tannins, especially h ydrolysable tannins. Tannase, a key enzyme in the degradation of hydrolysab le tannins, is present in a diverse group of microorganisms, including rume n bacteria. This enzyme is being increasingly used in a number of processes . Presently, there is a need for increased understanding of the biodegradat ion of condensed tannins, particularly in ruminants.