Screening and identification of a alfalfa condensed tannin-degrading bacterium
The study aimed to screen and identify tannin-degrading bacteria to provide microbial resources for the biodegradation of condensed tannins and to potentially expand the utilization of alfalfa.A strain capable of degrading condensed tannins was isolated from alfalfa root soil using a tolerance medium with condensed tannins as the sole carbon source.The strain underwent morphological observation,physiological and biochemical characterization,and 16S rDNA gene sequence comparison.The growth curve of the tannin-degrading bacteria was determined,and the effect of the strain on solid-state fermentation of alfalfa was observed.The results showed that the isolated strain was identified as Klebsiella sp.,named DN-2.Strain DN-2 entered the logarithmic phase in about 3 hours on a broth culture medium and reached an optical density(OD600nm value)of 2.405 at 600 nm after 24 hours.In the nutrient broth medium containing condensed tannins,it entered the logarithmic growth phase in about 4.5 hours,reaching the maximum OD600nm value of 2.35 after 20 hours,overall showing an extended lag phase and a shortened stationary phase for the strain.n-Butanol hydrochloric acid detection results showed that the degradation rate of condensed tannins in the culture fluid by strain DN-2 after 36 hours of growth was as high as 94.2％.The solid-state fermentation of alfalfa by strain DN-2 showed a tannin degradation rate of 59.73％after five days of fermentation treatment,indicating that strain DN-2 had a good degradation effect on condensed tannins in alfalfa.The study indicates that the screening of strain DN-2 has practical significance for the biodegradation of plant-derived condensed tannins and the development of microbial resources,and provides references for expanding the application of alfalfa in animal production.
alfalfacondensed tannin-degrading bacteriasolid-state fermentation of strains
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