Fermentation of alfalfa wet-fractionation liquids to volatile fatty acids by Streptococcus bovis and Megasphaera elsdenii

摘要

"Green juice", obtained by squeezing fresh alfalfa leaves inoculated with lactic acid bacteria, was fermented at room temperature for 7-21d to obtain 12-47glactic acidL~(-1). Inoculation of green juice with Streptococcus bovis and incubation at 39°C reduced fermentation time to 8-12h. The resulting "brown juice" from either fermentation had a pH of ~4.5 and a protein precipitate. Upon adjustment to pH 5.2-6.8 and inoculation with Megasphaera elsdenii, brown juice was fermented within 48h to up to 18g of mixed volatile fatty acids (VFA) L~(-1). Single-stage fermentation of green juice by both species in coculture typically resulted in overgrowth of S. bovis and acid inhibition of M. elsdenii, inhibiting VFA production. Because the juice fermentations are conducted without sterilization or supplemental nutrients, they can potentially contribute to an integrated process featuring protein recovery and fermentation of fractionated solids to VFA and other products.