DEGRADATION OF FRUCTANS BY EPIPHYTIC AND INOCULATED LACTIC-ACID BACTERIA AND BY PLANT ENZYMES DURING ENSILAGE OF NORMAL AND STERILE HYBRID RYEGRASS

Degradation of grass fructans by epiphytic or inoculated lactic acid b acteria during ensilage was examined using both normal and sterile hyb rid ryegrass. It was clear that even in the absence of bacteria fructa n degradation occurred, but at a significantly slower rate than in nor mal grass which had not been inoculated with lactic acid bacteria. Fru ctan degradation in sterile herbage suggests that plant fructan hydrol ases were partially responsible for this process in all herbages, irre spective of treatment. Inoculation of sterile herbage with a strain of Lactobacillus plantarum known to lack the ability to degrade grass fr uctans resulted in a slower rate of fructan breakdown than when inocul ated with Lactobacillus casei subsp. paracasei, a confirmed fructan de grader. In the later stages of the fermentation of uninoculated normal herbage when water-soluble carbohydrate appeared to be limiting, lact ic acid was fermented to acetic acid. However, this fermentation pathw ay was not observed in either of the inoculated silages. The results s uggest that silage inoculant bacteria possessing fructan hydrolase act ivity may have potential for improving silage fermentation, particular ly when late cut, low sugar grass containing a high proportion of fruc tans is ensiled.