| Antibiotic mycelial residues(ARMs)is a type of organic waste rich in available nutrients,produced during the process of microbial fermentation to produce antibiotics drug.Since ARMs contains a small amount of antibiotic residues and antibiotic resistance genes(ARGs),posing a potential environmental microbial resistance risk.it was listed in the Hazardous Material List of China in 2008,However,ARMs contains considerable available organic substances,which makes resource utilization an excellent treatment option.In this paper,gentamicin mycelial residues(GMRs)is selected as the research object.Based on the properties of gentamicin and GMRs,Microwave-alkaline pretreatment technology is adopted to investigate the pretreatment efficiency of GMRs disintegration and organic dissolution;the comprehensive utilization of anaerobic digestion(AD)-biogas residue(BR)utilization is employed the effects of wheat straw as additional carbon source,digestion temperature and retention time on the methanogenic performance of GMRs and the land utilization efficiency of BR as soil amendment,as well as the analysis,evaluation and the control of ARGs risk during AD of GMRs and land utilization of BR.This research tries to provide a theoretical foundation as well as technical support for the safe resource utilization of GMRs.Microwave-alkaline pretreatment technology was used to pretreat GMRs,the destruction efficiency of the structure of GMRs,the dissolution and release of organic matter were researched,and the enhancement effect of microwave heating and traditional heating(100℃)on alkaline pretreatment to pretreat GMRs were investigated and compared.The results showed microwave-alkaline pretreatment could effectively destroy the structure of GMRs to release intracellular organic matters.The content of soluble protein and polysaccharide increased significantly as the p H of microwave-alkaline pretreatment increased,while the particle size of suspended particles in GMRs decreased.,Microwave heating is a more efficient technology for strengthening alkaline pretreatment than traditional heating(100℃).Alkali has the ability to effectively destroy the GMRs structure and release intracellular substances.Microwave characteristics of rapid and uniform heating combined with alkaline pretreatment can produce a synergistic effect that significantly improves the efficiency of disintegration of GMRs and dissolution of organic.The results of batch experiment of anaerobic digestion showed that the methane yield of pretreated GMRs(p H 12,temperature of 100℃,time of 3 min)was 50% higher than that of untreated GMRs.Three-dimensional excitation-emission matrices(3DEEMS)analysis showed that Maillard reaction occurred when the p H of pretreatment was higher than 12,which resulted in a large amount of humic-like substances,melanoidin,an anaerobic digestion inhibitor,resulting in a significant decrease in methane yield of AD of GMRs.The optimum technological parameters were determined based on the efficiency of GMR disintegration,organic matter dissolution,and methane yield: p H 12,microwave irradiation for 3 min with temperature of 100℃.A continuous stirred tank reactor(CSTR)anaerobic digestion technology for GMRs was established by using crushed wheat straw(WS)as additional carbon source,and the efficacy of using BR as a soil amendment to improve soil quality and fertility was investigated.The anaerobic digestion performance under different CSTR operation conditions was investigated;the optimum anaerobic digestion technology parameters were determined: the ratio of GMRs to WS of 1:1(VS basis),the digestion temperature of 55℃,the retention time of 15 days,and the organic solid load of 3.14 g VS/L/d.AD performance with the methane yield of 342.88 ± 14.02 m L/g VS and the VS removal rate of 71.99%,increased by 22.05% and 20.17%,respectively,compared with the mesophilic AD(37℃)with GMRs.The addition of WS and elevating temperature hold the ability to enhance the hydrolysis efficiency,eliminate the inhibition of ammonia nitrogen,improve the solid reduction and methane yield performance,and hold shock load resistance.BR of anaerobic co-digestion of GMRs and WS as soil amendment could significantly increase the soil quality and fertility;the results of random forest and 3D-EEMs-Parallel factor analysis(PARAFAC)showed that humic acid from gentamicin residue could positively promote soil enzyme activity.The anaerobic digestion-biogas residue utilization mode was adopted to realize the comprehensive utilization of GMRs.Based on the succession of microbial community,the degradation of gentamicin and the abundance changes of ARGs during AD and land utilization,the control and mechanism of ARGs and the ARGs host,as well as the dissemination risk of ARGs were studied to evaluate the safety of resource utilization of GMRs.The results indicated that the dominant methanogen was Methanosaeta when the ratio of GMRs to WS is 1:1 for mesophilic AD;Methanosarcina became the dominant methanogen genus,which can produce methane through syntrophic acetate oxidizing-hydrogenotrophic methanogenesis under the conditions of stirring and high temperature.Shortening the retention time was conducive to increasing the abundance of Methanosaeta and the stability of the AD reactor.BR had a clear impact on the structure of soil microbial community as a soil amendment.The application of biogas residue increased the survival competitiveness of Gram-negative bacteria,and increased the abundance of microorganisms related to soil fertility and quality,such as Lysobacter and RB41.Gentamicin was degraded by the breakage of glycosidic bond during the treatment and utilization of GMRs,with a degradation rate of 98.63 ± 0.05%.The degradation of gentamicin has nothing to do with the modification of gentamicin inactivation enzyme,and there is no selective pressure on microbial resistance.The mixture of GMRs and WS with the ratio of 1:1,elevating the digestion temperature and shortening the retention time are beneficial to reduce the abundance of ARGs and ARGs host,reduce the risk of horizontal gene transfer through conjugation and transformation,and thus mitigating the risk of ARGs dissemination.Land utilization of BR as soil amendment reduced the abundance of ARGs introduced by BR,and on the premise of reasonable fertilization(for example,no more than twice a year),ARGs will not accumulate in the soil environment.Based on the regulation of AD conditions and the control of application frequency of BR,the abundance of ARGs,vertical and horizontal dissemination risks of ARGs was mitigated,and the safety of resource utilization of GMRs was effectively improved. |
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