Abstract: In the present work, we investigated the growth regularity of Lactobacillus acidophilus, screened out a high yield acid-producing strain and used the strain to ferment water extract from the young stems and leaves of Medicago sativa (alfalfa) cv. Zhaodong to precipitate alfalfa leaf protein by produced acids. The precipitation of alfalfa leaf protein from water extract from the young stems and leaves of Medicago sativa (alfalfa) cv. Zhaodong was studied by adjusting its pH. The effects of fermentation time, inoculum size, material/liquid ratio in raw material extraction on alfalfa leaf protein yield were explored. pH 3.0-3.7 proved optimal for precipitating alfalfa leaf protein. The optimal conditions for preparing alfalfa leaf protein were extraction material/liquid ratio of 1:20, fermentation time of 11 h, and inoculum amount of 107 cells/mL. Under the optimal extraction conditions, the extraction yield of alfalfa leaf protein was up to 45.08%.

Key words: alfalfa, leaf protein, Lactobacillus acidophilus, fermentation