Continuous fermentation process of fermented liquid feed

This study aims to evaluate the effects of fermentation strain, retention ratio, fermentation temperature, exogenous benzoic acid, and exogenous enzyme preparation on fermentation process and the nutritional value of feeds, by means of monitoring the variations invarious indicators of liquid feed during fermentation, including the pH, the numbers of Lactic acid bacteria (LAB), Escherichia coli (E. coli), mold, and yeast, acid-soluble protein content, and soluble sugar content. The experiment was performed using a corn-soybean-wheat bran mixture as the fermentation substrate, to select strains for producing liquid fermented feed. The results show that: 1) The selected LAB strain 28-7 has strong ability in inhibiting E. coli and producing lactic acid. The pH value of feed dropped to 4.45 after 6 hours of fermentation, and the E. coli cannot be detected. 2) During the continuous fermentation with the LAB strain 28-7, little difference showed in the effects on the pH or the numbers of LAB and mold in the fermented feed with retention ratio at 20%, 30% or 50%, and the E. coli was not detected. Therefore, the retention ratio of 20% can ensure a good fermentation. 3) The addition of exogenous non-starch polysaccharide enzyme can significantly increase the acid-soluble protein content, acid-soluble protein/crude protein ratio, and soluble sugar content in the fermented feed (P<0.05). The addition of exogenous benzoic acid can effectively inhibit moldmultiplication. 4) The acid-soluble protein and the acid-soluble protein/crude protein ratio significantly increased (P<0.05) with the fermentation at 37℃. The pH values of feed at 3-12, 20, and 37 ℃ were less than 4.0. The LAB number was more than 1010 CFU/mL. The E. coli, yeast and mold were not detected. The liquid fermentation technique was established in this study: Lactic acid bacteria strain 28-7 (inoculation amount 1.0×108 CFU/mL), non-starch polysaccharide enzyme (250 g/kg), and benzoic acid (0.1 g/kg) were simultaneously added at the beginning of fermentation. The production was proceeded with the fermentation period of 24 h, the retention ratio of 20%, and temperature at 3-12 ℃ (room temperature in winter), 20 ℃ (average room temperature in spring and autumn), and 37 ℃ (average room temperature in summer). The liquid fermented feed produced inthis process was light yellow in color, and rich in mild sour flavor; the pH value of feed was less than 4.0; the LAB number was more than 1010 CFU/mL; the content of acid-soluble protein and the ratio of acid soluble protein to crude protein significantly increased (P<0.05). The mold, yeast and E. coli were not detected. Compared with spring, autumn and winter, the acid-soluble protein content can be more easily increased in summer production (P<0.05).