Fate of Escherichia coli O157:H7 during composting of bovine manure in a laboratory-scale bioreactor.
Fate of Escherichia coli O157:H7 during composting of bovine manure in a laboratory-scale bioreactor.
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DOI：
10.4315/0362-028x-66.1.25
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发表时间：
2003
影响因子：
2
通讯作者：
Xiuping Jiang;J. Morgan;M. Doyle
中科院分区：
文献类型：
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作者：
Xiuping Jiang;J. Morgan;M. Doyle
在受控条件下，通过在生物反应器中堆肥这些成分，确定了接种牛粪堆肥成分中大肠杆菌O 157：H7的灭活概况。构建15升生物反应器以测定E. coliO 157：H7，以及堆肥过程中pH值、含水量、温度和好氧嗜温和嗜热菌数的变化。新鲜牛粪，小麦秸秆，棉籽粕，和硫酸铵相结合，以获得水分含量约。60%和29：1的碳/氮比。堆肥成分保持在21或50摄氏度的恒定外部温度下的生物反应器中。堆肥过程中，由于微生物的活动，成分发生自加热，生物反应器内发生分层温度。在21摄氏度的外部温度下，自加热发生0至3天，这取决于生物反应器内的位置。E.大肠杆菌O 157：H7种群在堆肥的最初24 h增加了1至2 log 10 CFU/g，并减少了约10 log 10 CFU/g。3.5 log 10 CFU/g，接近生物反应器底部，约在36 d的堆肥过程中，堆肥中部和顶部的菌落数为2 log 10 CFU/g。在50摄氏度的外部温度下。E.大肠杆菌O 157：H7的灭活速度较快（约100 μ g/ml）。4.9 log 10 CFU/g），靠近中间为4.0 log 10 CFU/g，靠近底部为5.9 log 10 CFU/g）。当接种在初始水平的CA。10（7）CFU/g。E.大肠杆菌O 157：H7在3个采样点均存活7 d，但不能存活14 d。在生物反应器的顶部，保持相对恒定的60%的水分含量，而在14天的堆肥中，底部附近的水分含量稳定地下降到37至45%。堆肥混合物的pH值降低至约1.5。1至3天内为6，随后增加至8至9。在这项研究中获得的结果表明，大种群（10（4）至10（7）CFU/g）的大肠杆菌O 157：H7存活36天，在堆肥过程中的生物反应器在外部温度为21摄氏度，但被灭活后7至14天，当外部温度的生物反应器是50摄氏度检测不到的水平。因此，被大量人口污染的粪便（例如，10（7）CFU/g）。大肠杆菌O 157：H7应堆肥超过1周，最好是2周，当保持在50摄氏度的最低温度。
Inactivation profiles of Escherichia coli O157:H7 in inoculated bovine manure-based compost ingredients were determined by composting these ingredients in a bioreactor under controlled conditions. A 15-liter bioreactor was constructed to determine the fate of E. coli O157:H7 and changes in pH, moisture content, temperature, and aerobic mesophilic and thermophilic bacterial counts during composting. Fresh cow manure, wheat straw, cottonseed meal, and ammonium sulfate were combined to obtain a moisture content of ca. 60% and a carbon/nitrogen ratio of 29:1. The compost ingredients were held in the bioreactor at a constant external temperature of 21 or 50 degrees C. Self-heating of the ingredients due to microbial activity occurred during composting, with stratified temperatures occurring within the bioreactor. At an external temperature of 21 degrees C, self-heating occurred for 0 to 3 days, depending on the location within the bioreactor. E. coli O157:H7 populations increased by 1 to 2 log10 CFU/g during the initial 24 h of composting and decreased by ca. 3.5 log10 CFU/g near the bottom of the bioreactor and by ca. 2 log10 CFU/g near the middle and at the top during 36 days of composting. At an external temperature of 50 degrees C. E. coli O157:H7 was inactivated rapidly (by ca. 4.9 log10 CFU/g at the top of the bioreactor, by 4.0 log10 CFU/g near the middle, and by 5.9 log10 CFU/g near the bottom) within 24 h of composting. When inoculated at an initial level of ca. 10(7) CFU/g. E. coli O157:H7 survived for 7 days but not for 14 days at all three sampling locations, as indicated by either direct plating or enrichment culture. At the top of the bioreactor a relatively constant moisture content of 60% was maintained, whereas the moisture content near the bottom decreased steadily to 37 to 45% over 14 days of composting. The pH of the composting mixture decreased to ca. 6 within 1 to 3 days and subsequently increased to 8 to 9. Results obtained in this study indicate that large populations (10(4) to 10(7) CFU/g) of E coli O157:H7 survived for 36 days during composting in a bioreactor at an external temperature of 21 degrees C but were inactivated to undetectable levels after 7 to 14 days when the external temperature of the bioreactor was 50 degrees C. Hence, manure contaminated with large populations (e.g., 10(7) CFU/g) of E. coli O157:H7 should be composted for more than 1 week, and preferably for 2 weeks, when held at a minimum temperature of 50 degrees C.