Research On Preparation Of The Protein Of White Lees By Complex Bacteria Biotransformation

Distiller’s grains are mainly wastes generated of wine manufacturing. It contains a high protein, and it is a high-quality vegetable protein material. Due to the high crude fiber content, the deep processing and utilization of it is restricted to a certain extent. Aimed at improving the protein content and reducing the crude fiber content of white lees’ fermentation products, the tests take advantage of the synergies of complex strains through solid state fermentation. The significance of this study is to determine the optimal strains combination and fermentation parameters. It provides the basis for the better utilization of distiller’s grains and the development of food protein by white lees. Study includes the following three experiment parts:Experiment part 1 Tablet satisfactory test and fermentation test of single strainThe tablet satisfactory test is taken to observe the growth of each strain. And the fermentation medium is based on the leaching liquor of basic solid medium extract of white less. The results show that the three strains can grow well on the medium. It means that the basic solid state fermentation medium of white lees can meet the growth demands of Bacillus subtilis、Candida utilis and Geotrichum candidum, and we can choose them as the fermentation strains. The single strain fermentation test studies the effects of moisture content of materials, fermentation time, inoculum, addition amount of urea on the content of crude protein(CP), true protein(TP), crude fiber(CF) of fermentation products. It will provide basic reference for the late mixed fermentation conditions. The results of single strain fermentation tests show that the suitable fermentation parameters are as follows: the 60% moisture content of materials, ferment 5d with the inoculation of 20% Bacillus subtilis, the addition of 2.0% urea; the 60% moisture content of materials, ferment 3d with the inoculation of 20% Candida utilis, the addition of 2.5% urea; the 60% moisture content of materials, ferment 3d with the inoculation of 15% Geotrichum candidum, the addition of 2.5% urea. In addition, Bacillus subtilis and Geotrichum candidum have better capability to degrade cellulose, CF decreased by 4.26% and 3.90%; Candida utilis and Geotrichum candidum have better capability to transform protein, TP increased by 9.48% and 9.60%.Experiment part 2 Antagonism test and fermentation test of mixed strainsThe antagonism test is inoculating Bacillus subtilis 、 Candida utilis and Geotrichum candidum by intersect cross-crossed on ordinary nutrient agar medium, at 30℃ with 24 h. The results show that the three strains grow well, and the intersect points don’t have the phenomenon of colony atrophy and disappearance. It means that there is not antagonistic effect between the strains, and we can use them for mixed fermentation tests. The fermentation test of mixed strains is inoculating the total inoculation of 15% with each two strains(ratio of 1:1) and three strains(ratio of 1:1:1), at 30℃ with 3 d, on the basic solid medium. Compared with the blank control group, the CP, TP, CF content of two strains and three strains show that: the three strains has the best result, with 28.95% CP, 22.63%TP, 19.96% CF.Experiment part 3 fermentation test of three strainsThe purpose of this test is to determine the process parameters of solid-state fermentation with three strains. With the indicators of the CP, TP, CF content of fermentation products, the single factor tests with three strains are taken based on four factors of inoculat methods, inoculum, addition amount of urea, and the addition amount of wheat bran. And a orthogonal trial is taken to determine the optimal fermentative parameters of the four factors with each factor being designed at four levels.Finally, the verification tests are taken. Due to cost reasons, the most optimum fermentation conditions are: the first stage with 10% Geotrichum candidum and 5% Bacillus subtilis at 30℃ with 24 h, the second stage with 5% Candida utilis at 30℃ with 72 h continued; the addition of 2.5% urea and the addition of 15% wheat bran. Under these conditions, the conversion rate of protein is best, content of CP up to 32.09%, TP up to 24.85%, CF is reduced to 17.66%.In summary, we should take advantage of white lees with the synergies of complex strains through solid state fermentation. It is better to improve the protein content, especially TP content of fermentation products by making full use of the nutrients of white lees. It has good prospects for development.