The Analysis Of Biological Characteristics In The Co-composting Process Of Penicillin Fermentation

Antibiotics fermentation dregs (AFDs) are the by-products in themanufacturing process of Ferment Antibiotics. Incineration is the onlyrecommended technology for AFDs disposal. High moisture content of AFDsincreased the incineration cost. Moreover, organic composition like protein occupies90%of AFDs, which makes incineration even unsustainable treatment method. Fewresearches have studied using composting to treat AFDs, however, they only focusedon the performance of the composting process, further research on biologicalcharacteristics in AFDs composting need to be carried out. In this research, anauto-control aerobic composting system was used to treat penicillin fermentationdregs (PFDs). Physicochemical and biological characteristics were investigatedthroughout the composting process. Maturity and safety of the compost wereevaluated.The PFDs were composted together with municipal sludge, saw dust andwood shavings. The composting of municipal sludge without dregs was used ascontrol (CK).The basic physicochemical properties, enzymatic activities, populationof cultivable microorganisms, resistance genes and microbial community structurewere analyzed. The main results are as follows：The compost odor was gradually reduced and eventually disappeared, while thematerial color changed from yellowish to black during the composting process.There were more than3days during the composting process that the temperature ofthe compost pile was over55℃, and the maximum temperature reached58.5℃.Themoisture content was48.21%at the end of the treatment, decreased by25%compared to that at the beginning. pH of the composting was8.2, Total organiccarbon and total nitrogen content of the finial compost decreased by3.4%and21.3%, respectively. The seed germination rate increased from0%at the beginningstage of the composting to over60%at the end. During the composting process, thetrend of catalase activity did not change, acid phosphatase activity decreased at firstbut later levelled off, cellulase activity firstly increased and then decreasedsubsequently. All the three kinds of enzymatic activities in the PFDs compostingwere higher than that in the CK group. Urease and proteinase activities at the end ofthe composting increased by50.6%and10.5%, respectively, compared to those inthe beginning. Invertase activities in both PFDs and CK group increased at first andthen decreased.The microorganism culture method showed that the number of cultivablebacterial firstly increased and then decreased while actinomycetes number increased at first, then decreased and increased again to a stable level. The number of bacteriaand actinomycetes in PFDs composting were lower than those in CK group at thebeginning of the composting. While at the thermophilic phase, the number ofbacteria and actinomycetes in PFDs composting turned higher than those in the CKgroup. The number of fungi declined throughout the compostingTerminal restriction fragment length polymorphism (T-RFLP) was used tomonitor the microbial community change during the composting. The resultsshowed that the diversity of the microbial community connected with thecomposting process. The diversity was less at the thermophilic phase while itincreased at the maturity stage. The content of antibiotic resistance genes (ARGs)was also analyzed during the composting. Three types of beta-lactam antibioticgenes (TEM, SHV, CTX) were used in qualitative PCR, only TEM was detected inAFDs composting. No ARGs was detected in the CK group. The TEM-ARGs in thecomposting were further quantified by Q-PCR using a SYRB GreenⅠ. The resultsshowed that the quantity of TEM gradually increased during the composting process.It meant that ARGs quantity can not be decreased by aerobic composting and on thecontrary, it can be promoted someway.The moisture content of the final composting product was higher than statestandards and the organic content, heavy metals contents were all satisfied theNY-2012standard. The composting product is a kind of high quality fertilizerconsidering about the physicochemical properties, however, the ARGs detected inthe product must be removed before it applied in the field.