Chemical studies with silage microorganisms in artificial media and sterile herbages

Abstract

AbstractThe fermentation changes in artificial media and in sterile herbages inoculated with strains of yeast, hetero‐and homo‐fermentative lactic acid bacteria isolated from silage were studied in two experiments. In the first, using malt extract broth, four treatments were employed: aerobic, high level of glucose; aerobic, low level of glucose; anaerobic, high level of glucose; anaerobic, low level of glucose. The pH decreased in all cultures. There were no appreciable differences in pH among the cultures of the heterofermentative lactic acid bacterium, but in the cultures of the homofermentative organism there was a greater decrease in pH aerobically than anaerobically. The lowest pH values in the yeast cultures, occurred in the high glucose treatments both aerobically and anaerobically. In all the yeast cultures, acetic, propionic, butyric, isobutyric and isovaleric acids were present. The heterofermentative lactic acid bacterium produced only acetic acid, the greatest amount occurring under aerobic conditions. Ethanol was detected in the culture of the heterofermentative lactic acid bacterium but not in that of the homofermentative organism. Relatively large amounts of i‐pentanol were found in the aerobic yeast cultures. In the second experiment, inoculated grass was ensiled with similar treatments to those used in the first experiment. Two incubation periods, 3d and 10d were used. The pH values in all treatments were high (> pH 5.0). In aerobic conditions, the lactic acid contents after the 10d incubation were higher than after 3d. The losses of water soluble carbohydrates during fermentation were greater in the aerobic than anaerobic treatments. Acetic acid was present in all cultures but the higher volatile fatty acids (C3‐iC5) were only detected in appreciable amounts in the aerobically treated herbages after 10d. In addition to ethanol, n‐propanol and i‐butanol were also present in all the 10d anaerobic treatments. i‐Pentanol occurred in both the aerobic and anaerobic treated herbages.