Phenotypic and phylogentic characterisation of tannin degrading/tolerating bacterial isolates from the rumen of goats fed on pakar (Ficus infectoria) leaves

Abstract

The tannin degrading/tolerating bacteria were isolated from goat rumen fed on tannin rich diet on a medium containing 1% tannic acid. One hundred and twenty five isolates were picked up and screened for their potential to grow on a medium containing tannic acid as one of the ingredients and eight best isolates were selected for further characterisation. The isolates were coccoid to cocco-bacillary. Two out of eight isolates were Gram negative and the rest were Gram positive. All the isolates exhibited tannase activity with maximum of 29.0 units in isolate numbers 5, 6 and 7 and were able to grow on glucose, cellobiose, galactose, fructose, starch and sucrose but none of the isolates was able to grow on rahmnose. The isolates were tolerant to the presence of gallic acid in the medium up to 20mM, but pyrogallol, ferulic acid and coumaric acid were toxic at higher concentrations (20mM). True degradability of pakar leaves was increased by 9.7% by inclusion of live cultures of isolate number 6 (Accession no. HM771331) in the incubation medium. The phylogenetic analysis of 16S rRNA sequences of the isolates made a tight cluster with Streptococcus gallolyticus showing similarity ranging from 97.4% to 99%. The goat isolate number 6 (Accession no. HM771331) was tolerant to the phenolic monomers, exhibited tannase activity and improved in vitro true digestibility of tannin rich pakar leaves. The isolate appears to have a potential to be used as microbial feed additive to improve the utilisation of poor quality tannin containing feeds by the ruminants.