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

• Published in: Bioresource technology Vol. 142; pp. 88 - 94
• Main Authors: Weimer, P.J., Digman, M.F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2013; Elsevier
• Subjects: Alfalfa; Bacteria; Biological and medical sciences; Biotechnology; Fatty acids; Fatty Acids, Volatile - metabolism; Fermentation; Fundamental and applied biological sciences. Psychology; Inoculation; Juices; Lactic acid; Medicago sativa - metabolism; Megasphaera - metabolism; Megasphaera elsdenii; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; Streptococcus bovis - metabolism; Volatile fatty acids; Wet fractionation; Alfalfa; Lactic acid; Fermentation; Volatile fatty acids; Wet fractionation; Fractionation; Medicago sativa; Streptococcus bovis; Streptococcaceae; Veillonellaceae; Leguminosae; Dicotyledones; Angiospermae; Volatile fatty acid; Bacteria; Micrococcales; Spermatophyta; Megasphaera elsdenii; Fodder crop; Lucerne
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2013.05.016

•Alfalfa juice is rich in sugars, starch and a recoverable protein fraction.•Streptococcus bovis enhanced fermentation of alfalfa juice to lactic acid.•Megasphaera elsdenii effectively converted lactate to volatile fatty acids.•No chemical pretreatment, sterilization or nutrient supplementation was required.•A two-stage fermentation generally outperformed a single stage fermentation. “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.