Role of Yeasts and Clostridia in Silage Deterioration: Identification and Ecology

摘要

Conditions influencing the growth of yeasts and clostridia during fermentation and deterioration of grass silage were studied. Methods for quantification and identification for these organisms were developed and evaluated. Lactate-assimilating yeasts were estimated on a substrate containing yeast nitrogen base and lactate. Lactate-fermenting Clostridium tyrobutyricum was confirmed by measuring lactate dehydrogenase (LDH) activity and testing for the ability to reduce the dye neutral red. No other clostridia species occurring in silage showed lactate dehydrogenase activity. Yeast development was investigated in grass silage. Laboratory, pilot-scale and full-scale experiments showed that yeasts usually initiated the deterioration and were succeed by Bacillus spp. at temperatures above 40C. Strains of C. tyrobutyricum were inhibited by 0.5% lactic acid at a pH of about 4.7-4.9 and an optimal temperature of 37C. The number of clostridial spores increased during aerobic deterioration.