Study On Dissolved Organic Matter,Microbial Community Succession And Function During Solid-state Fermentation Of DDGS And Sugarcane Pith

Distillers dried grains with solubles(DDGS),a byproduct of ethanol refiners,are widely used in animal husbandry,aquaculture and poultry feed because of their rich nutrients.However,the limiting amino acids and phytic acid in DDGS affected the absorption and utilization of nutrients in animals with a single stomach.Solid state fermentation can transform macromolecular substances and antinutritional factors into high-quality,non-toxic feed ingredients or commercial feed.Microbial community succession can affect the composition of dissolved organic matter(DOM),and then affect the quality of solid fermentation feed.Studies on the relationship between DOM and microbial community mainly focused on the environment and composting,but there are few studies on solid state fermentation of animal feed.Therefore,in order to provide more information,this study explored the characteristics of environmental factors,DOM and microbial community during the solid-state fermentation of DDGS and sugarcane pith at different oxygen levels.The results indicated that under aerobic fermentation(AF),the DOM content decreased from 32.61 mg/g to 14.14 mg/g,while in anaerobic fermentation(ANF),it decreased from 32.61 mg/g to 30.83 mg/g.In AF,phenols and alcohols were the first to be consumed,whereas in ANF,lipids and proteins were consumed first.AF had higher degradation rates of cellulose,hemicellulose,and lignin(6.67%,39.93%,36.50%)compared to ANF(0.69%,18.36%,9.12%).The dominant microbial groups in both processes were Firmicutes,Actinobacteria,and Ascomycota.Short-term fermentation(0-4 days)promoted the growth of aerobic fermentation bacteria,including Bacillus ginsengihumi and Bacillus coagulans.Moreover,the increased relative abundance of adenylate kinase and DNAdependent RNA polymerase indicated a high level of microbial growth and metabolic activity.On the other hand,long-term fermentation(0-50 days)supported the growth of Lactobacillus plantarum in anaerobic fermentation.The relative abundance of carbohydrate metabolism increased as fermentation progressed,corresponding with the degradation of lignocellulose and DOM consumption.Co-occurrence network analysis showed that the microbial community interaction in AF was weaker than that in ANF.Myroides odoratus,uncultured Myroides sp,unclassified Pseudochrobactrum,and unclassified norank Bradymonadales were key microbes in the bacterial co-occurrence network in AF,while Lactobacillus crustorum,Lactobacillus brevis,and Lactobacillus nagelii were key microbes in the fungal co-occurrence network.p H,OM,and DOM were identified as the main driving factors of microbial community evolution by distance-based redundancy analysis.Bacillus ginsengihumi and Issatchenkia orientalis played important roles in OM degradation and DOM formation.In conclusion,the action of endogenous microorganisms results in higher rates of DOM consumption and lignocellulosic degradation in aerobic fermentation compared to anaerobic fermentation.Moreover,the microbial community interaction in aerobic fermentation was weaker than that in anaerobic fermentation.Adjusting environmental factors to manipulate the abundance of key microorganisms can affect the degradation of lignocellulose and DOM transformation,thereby improving the fermentation efficiency and quality of feed.