Solid-state Fermentation Of Bio-feed Using By-products Of Deep Processing Of Corn

Corn is one of the main food crops in China,and the total production of it in China has reached 260 million tons in 2020.Corn deep processing industry,with main products including corn starch,starch sugar,citric acid,fuel ethanol and et.al,has developed rapidly with the increase of corn production.At present,most of the by-products of corn starch production,such as corn bran and corn steep liquor,and citric acid production,like Aspergillus niger residue and gypsum,have been sold out at low prices or piled up everywhere,not only bringing about the waste of resources,but also aggravating the environmental pollution.Therefore,it is of great significance for feed industry and corn deep processing industry to comprehensively utilize the byproducts of corn deep processing as raw materials to produce green,nutritious and economical biological feed.At the same time,the bacterial strains that can effectively degrade deoxynivalenol were screened to provide technical support for the removal of mycotoxin in feed.Firstly,the filter paper method was carried out to investigated the interaction relationship between 9 probiotics（Saccharomyces cerevisiae,Bacillus subtilis,Bacillus licheniformis,Bacillus velezensis,Lactobacillus plantarum,Lactobacillus buchneri,Lactobacillus casei,Pietococcus pentosaccharides and Lactobacillus rhamnosus）.There are three main phenomena on the plate:first,there is an obvious transparent circle around the filter paper,which indicates that there is antagonistic effect between strains;Secondly,there are bacteria growing around the filter paper,which indicates that the bacteria on the filter paper are dominant;Third,there was no transparent circle or bacterial growth around the filter paper,indicating that there was no antagonistic effect between strains.According to the inhibition degree between species,five probiotics（Saccharomyces cerevisiae,Bacillus subtilis,Bacillus licheniformis,Lactobacillus planatum and Lactobacillus casei）were selected as the fermentation strains.The effect of corn steep liquor concentration in seed medium on cell growth was investigated.The results showed that 5 g/L corn steep liquor was added to Saccharomyces cerevisiae and Bacillus subtilis at p H 6.5;Bacillus licheniformis,Lactobacillus plantarum and Lactobacillus casei were added with 15 g/L corn steep liquor.The growth curve of each fermentation strain and the relationship curve between OD₆₀₀and the number of live bacteria were drawn,and the seed culture time was determined to be 18 h.Secondly,single factor and orthogonal experiments were carried out to investigate the effects of loading amount,initial p H,water content and inoculation amount on feed fermentation,and the optimized technological parameters of solid culture were as follows:loading amount 70%,initial p H 5.8,water content 55%and inoculation amount 12%.Based on the optimized conditions,the color and texture were uniform and loose after fermentation;The total count of viable bacteria was 9.6×10⁹cfu/g;Crude protein content reached 21.2%,increased by 14.3%compared with that before fermentation;p H was 4.8.The electron micrograph showed that the surface structure of fermented corn bran was damaged and became rough and porous.Finally,28 strains of DON degrading bacteria were isolated from different samples.The degradation ability of DON degrading bacteria in LB medium and corn steep liquor was investigated.When the concentration of DON was 2 ppm in LB medium,A2 had the highest degradation rate of DON（37.75%）;In the corn steep liquor medium with DON concentration of 5 ppm,the DON degradation rate of the 3#2 generation was the highest,which was25.25%.