Directional Optimization Of Acetic Acid Production From Anaerobic Fermentation Of Peanut Meal By Homoacetogens/nZVI

Anaerobic fermentation technology is recognized as an effective technique for the resource treatment of organic waste in recent years,producing high value-added products of Volatile Fatty Acids（VFAs）,which can provide raw materials for the synthesis of polyhydroxyalkanoate（PHA）.Peanut meal is one of the organic solid wastes rich in nutrients,producing even carbon VFAs through anaerobic fermentation.However,the insufficient proportion of acetic acid in fermentation products and low COD utilization rate affect the efficiency of subsequent synthesis of PHB monomer.Therefore,it is essential to realize acetic acid’s directed production by anaerobic fermentation of peanut meal.According to the above problem,this article by inoculation with municipal sludge domesticated type produce acetic acid bacteria,plus cheap chemical materials nanometer zero-valent iron（nZVI）these two methods,to improve the peanut meal in the middle of the acetic acid bacteria fermentation process of the organic matter enrichment and hydrolysis acidification efficiency,and applied to the CSTR abortion acid in a row,to achieve the sustainable of the peanut meal directional acetic acid production.In the CSTR reactor,the municipal sludge enrichment homogeneous acetic acid-producing bacteria were acclimated by continuous inflow by stages.The effects of sludge concentration and influent COD on the stable acetic acid production from the acclimated sludge were investigated.Combined with the sequential batch anaerobic reactor,the effects of different inoculation ratios of domesticated sludge and different NZVI dosage ratio on the acetic acid production efficiency of peanut meal by anaerobic fermentation were studied.The optimal method with the best comprehensive benefit was selected from the two systems and applied to the continuous acid production mode of CSTR.The changes of acetic acid,VFAS,SCOD,polysaccharide,protein,and other essential indexes,as well as the succession of the microbial community in each anaerobic system,were investigated.The results show that the acclimated sludge has a certain tolerance to ammonia nitrogen.When the MLSS of the sludge is stable at 4300～4900mg·L^-1 and the influent COD is 8000mg·L^-1,the acetic acid production efficiency of the sludge is stable at the end of the C stage of the accusation cycle,and the ratio of acetic acid to even VFAs is close to 100%.When the inoculation ratio of acclimated sludge was 10%（relative dry weight）,acetic acid yield in sequential batch anaerobic reactor was the best,the peak value was 4646.75±634mg·L^-1,acetic acid/TVFAs was as high as 64.56%,and the nonlinear fitting degree between protein and NH₄⁺was high.In addition,when the ratio of NZVI was 10000mg·L^-1,the accumulation concentration of acetic acid from peanut meal was higher,and the acetic acid/TVFAs was62.41%,which improved the utilization rate of COD,but the accumulation amount of NH₄⁺began to inhibit the activities of hydrogen-acetic acid-producing bacteria and acetic acid-producing bacteria of the same type,and the nonlinear fitting degree between protein and NH₄⁺was low.10%inoculation sludge application CSTR continuous flow fermentation experiments,startup phase TVFAs highest shall be increased to 19529.45±789.85 mg·L^-1,mainly to produce acetic acid as the primary form of produce acid,acetic acid/ECFA steady at76.8%,continuous flow phase steady at 89.07%,orientation is practical to treat the acetic acid production,accumulation of NH₄⁺concentration in the process of running wasn’t up to produce hydrogen to produce acetic acid bacteria and type with the concentration of acetic acid bacteria is restrained the threshold.The results of 16SrRNA high throughput sequencing showed that the diversity of hydrolytic acidizing bacteria group would increase significantly in the process of CSTR domestication sludge.In the stable period of domestication,the phase pairs of Firmicutes reached 76.82%,and the same type of acetic acid-producing bacteria in sludge was the dominant group,and the most dominant bacteria was the dominant bacteria Clostridium;after inoculating domesticated sludge,the diversity of acid-producing bacteria in the batch anaerobic reactor will increase,and the dominant bacteria begin to succession to Bacteroides.Similarly,the relative abundance of Bacteroides will increase from the start stage of CSTR to continuous flow.The relative abundance of Bacteroides will increase,and the relative abundance of Bacteroidales will be one of a significant improvement.