Study On The Preparation Of Feed Additives By Fermentation Of Poplar Sawdust Waste Enzymatic Hydrolysate

The development of China’s aquaculture industry is very rapid,with a total annual feed consumption of 200 million tons and import dependence close to 80%.Feed additives are the core of the feed industry.The development of new feed materials and feed additives can not only alleviate the contradiction between domestic supply and demand,and reduce foreign dependence,but also help to upgrade the industrial structure and form a virtuous circle for the development of China’s entire livestock industry.In this paper,the enzymatic hydrolysate of poplar wood chips is used as a carbon source to replace food crops.The feasibility of Saccharomyces cerevisiae and Propionibacterium acidipropionici to use enzymatic hydrolysate was studied,and the fermentation process was optimized,in order to provide new ideas for the source of feed additives and the production process.The main conclusions are as follows:(1)Using 5%dilute acetic acid,the poplar wood chips were pretreated under the conditions of solid-liquid ratio 1:5,170℃ for 30 minutes,and the solid residue after pretreatment was taken as the research object.The effect of ratio,enzyme addition amount,pH and enzymatic hydrolysis time on the enzymatic hydrolysis effect was determined to be the best enzymatic hydrolysis conditions:solid-liquid ratio 1:6,enzyme addition amount 22.5 FPU/g substrate,pH 4.8.The reaction time was 48 h,and the enzymatic hydrolysate containing glucose 55 g/L was obtained.(2)Saccharomyces cerevisiae GSH2 is one of the strains with the strongest selenium-tolerant properties preserved in our laboratory.The feasibility of the strain GSH2 to utilize the enzymatic hydrolysate of poplar wood chips was investigated,and the addition amount and addition period of Na2SeO3 were studied under the existing fermentation culture mode.The appropriate amount of selenium is 5.3 mg/g dry cell weight,and sodium selenite is added to the concentrated enzymatic solution in the early,middle and late stages of the logarithmic growth of GSH2.The yeast biomass increased by 38.1%,55.9%,and 65.1%compared with the pulsed addition of sodium selenite,respectively;the initial yeast selenium content of the unit added sodium selenite was the highest,reaching 4006 μg/g dry cell weight,and the biomass added later The highest is 28.57 g/L.The total selenium content is not much different in the middle and late stages.Due to the higher biomass in the later stage,sodium selenite was added at the later stage of logarithmic growth.(3)Enzyme hydrolysates with initial glucose concentrations of 25 g/L,50 g/L,and 75 g/L were used to culture P.acidipropionici,and the best culture mode for propionic acid fermentation by P.acidipropionici was explored.The results show that when the glucose concentration is between 25 and 50 g/L,the specific growth rate of the bacteria and the specific synthesis rate of the product are higher,and the production intensity is higher than 0.2 g·L-1·h-1.In order to take into account the production efficiency,the initial The sugar concentration is 50 g/L.The constant-speed feeding method can only maintain the basic growth of the bacteria,and the sugar-acid conversion rate is only 24%;the pulse-feed method improves the sugar-acid conversion Rate,pulse feeding in two times until the sugar concentration of the fermentation broth reaches 25 g/L,and the concentration of propionic acid reaches 34 to 36 g/L at the end of the fermentation,which is about 51.9%higher than that of constant-speed feeding.