Bioconversion of citric acid waste into multi-enzyme protein feed

摘要

There are much β-glucosan in grist such as barley and oat, they can dissolve in water to form viscous gel and become nutriment-resistant factor. The factor inhibits the animal, especially the cub from utilizing nutriment. The animal's utilizing rate of feed can improve effectively if protease, cellulase and β-glucosanase are added into the feed. These enzymes will not affect the enzyme-producing ability of intestinal microorganisms of the animals themselves. Some research indicate that adding feeding multi-enzyme can reduce feed use everyday of meat-producing and egg-producing chicken, but the fairly low level of protein and amino will not affect their producing ability. If the enzyme formula of feed use everyday is given a certain apparent energy value (AEV), the metabolite energy of the meat-producing chicken can reduce 0.5 percent and the digestible lysine and Met can reduce 5 percent or even 9 percent. The output of the citric acid is the highest among the organic acid that are produced by biochemical technique in the world and our country's citric acid productivity is quite large. Citric acid waste is the squeezing waste of fermentation liquid in citric acid factory. It cost 2 tons of waste to get 1 ton citric acid The main components of the waste are (60°C, dried for 4-5 hours): Crude proteins (calculated based on dried medium), 10.98%; crude cellulose, 21.36%; crude fats, 14.96%; extracts free of nitrogen, 37.23%; crude ash contents, 7.09%. Cellulose takes the most part of the waste and the content of protein is low. If this waste is used to feed animal directly, the edibility and digestibility are fairly bad, but if cellulose in it is transformed by microorganism into tropina, the digestibility will be improved and we can not only get feed with high amount of protein but solve the environmental pollution problem partly. Taking account of economical problem, solid-state fermentation cost fewer and simplified the downstream technique, so it is quite suitable for our country. For the advantages above, we did some researches on the production of multi-enzyme protein feed from citric acid waste with solid-state fermentation. The experiment results indicated that the feed we got were rich of acid protease, cellulase and β-glucosanase with the increasing of tropina and these increased the value in use of the protein feed.