Selective Proliferation of Lactic Acid Bacteria and Accumulation of Lactic Acid during Open Fermentation of Kitchen Refuse with Intermittent pH Adjustment

Abstract

When minced and autoclaved model kitchen refuse was inoculated with a small amount of non-autoclaved model kitchen refuse as seed culture, incubated at 37°C for 3-5 days and intermittently pH neutralized, 27-45 g/l of lactic acid was accumulated with a small amount of acetic acid and ethanol. The highest accumulation and highest productivity levels of lactic acid were observed at an initial and adjusted pH of 7.0 and a 6 h interval of pH adjustment. After several hours of lag, the lactic acid bacteria became the dominant cell type during the incubation, while the number of coliform bacteria and clostridia decreased. Such selective and stable accumulation of lactic acid was achieved in dozens of different experiments with various refuse preparations. In contrast, with continuous pH adjustment, Iactic acid once accumulated was labile and a small amount of butyric acid was produced, increasing the number of clostridia. The dominant bacteria isolated from the fermentation with intermittent pH adjustment were identified as Lactobacillus plantarnm and L. brevis.