Anaerobic degradation of tannins in Acacia nilotica pods by Enterococcus faecalis in co-culture with ruminal microbiota

Abstract

Tannins are water-soluble polyphenolic compounds present in plant tissues. The two classes of tannins— hydrolysable (HT) and condensed (CT)—are generally regarded as anti-nutritional factors for ruminants, as they form complexes with proteins, including enzymes (Goel et al., 2005a, b), resulting in a remarkable reduction in the biodegradation of the fibrolytic polymers in the rumen, feed intake and dry matter digestibility (McSweeney et al., 2001). Tannic acid (TA), a typical hydrolysable tannin, is even toxic to both ruminant and monogastrics, particularly when it is available in the diets of those animals in excessive amounts (Zhu et al., 1992). However, ruminants have developed an adaptation mechanism against tannins via a microbial ecosystem inhabiting in their gastrointestinal tract (Goel et al., 2005a).