[WATER] Competitive exclusion as a means to reduce E. coli regrowth in digested sludge

[水] 竞争排除是减少消化污泥中大肠杆菌再生的一种手段

• 批准号: NE/I018247/1
• 负责人: James Harris
• 金额: $ 8.58万
• 依托单位: CRANFIELD UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI018247%2F1
• 关键词: WATER; Competitive; exclusion; means; reduce

The recycling of sludge to agriculture is regarded as the Best Practical Environmental Option in Europe. However, there are many challenges with the practice with concern about the risk of pathogen transfer to farm produce being a major issue. In recent years, it has been reported that numbers of Escherichia coli (E. coli) increase significantly following centrifugation. This is known as the E. coli regrowth phenomenon and it is of serious concern because E. coli is used as an indicator of the microbiological quality of sludge-derived products and compliance failure of the quality standards would result in higher disposal costs and loss of consumer confidence in the industry. It has been proposed that the apparent sudden increase in E. coli numbers in sludge subject to centrifugal dewatering is caused by reactivation of viable but nonculturable cells. Subsequent rapid growth of E. coli in the first few days of cake storage following dewatering is likely to be caused by the combination of a ready supply of nutrients and a lack of microbial competition for those nutrients. The hypothesis to be tested in this research is that the regrowth of E coli in stored sludge can be reduced by the application of the competitive exclusion principle; i.e. by competition between E. coli and fast-growing non-pathogenic bacteria that will be introduced to the dewatered sludge. The principle of competitive exclusion has been used successfully as a means of infection control for many years in the food industry. In this research we aim to develop inocula of differing microbial community composition and evaluate their ability to suppress the growth of E. coli in digested sludge. Objective 1: Test the competitive exclusion concept To test the basic premise of the research, a controlled and replicated bench-scale experiment will be designed in which sludge samples are sterilised and then re-inoculated with E. coli and competing microorganisms. In this experiment the E. coli will be challenged with inocula which present differing degrees of competition for available resources. Where the E. coli are presented with no or limited competition we would expect an increase in population. Where E.coli have to compete with a diverse and well adapted community for available resources we would expect population growth to be slower or absent. Objective 2: Optimise the competitive exclusion product Once the competitive exclusion concept has been successfully tested a competitive exclusion product will be optimised. We will investigate: (i) What is the best source of the challenge inoculum - for example from soils or from digested cake itself. (ii) How big does the competing population need to be? Is a seed population sufficient to compete with E. coli? Or is it necessary for the competitive exclusion product to reach a certain size before it is capable of competing? (iii) How important are key characteristics of microbial community structure of the competitive exclusion product. Measurements of the structure of the microbial community will be made by means of phospholipid fatty acid (PLFA) phenotypic profiling. Objective 3: Scale-up Once proven on bench scale, the culture work will be scaled up using a pilot-scale fermenter. Should the results of this pilot-scale work be promising there will be the opportunity to trial the process at full scale at a United Utilities facility.

将污泥回收为农业被认为是欧洲最佳的实际环境选择。但是，这种做法存在许多挑战，因为人们担心将病原体转移到农产品的风险是一个主要问题。近年来，据报道，离心后大肠杆菌（大肠杆菌）的数量显着增加。这被称为大肠杆菌再生现象，这引起了人们的严重关注，因为大肠杆菌被用作污泥衍生产品的微生物学质量的指标，而质量标准的合规性失败将导致更高的处理成本和消费者对行业的信心丧失。已经提出，受离心脱水的污泥中大肠杆菌数量的明显突然增加是由可行但不可培养的细胞重新激活引起的。随后在脱水后的蛋糕储存的最初几天内，大肠杆菌随后的快速生长可能是由于现成的养分供应和缺乏对这些营养素的微生物竞争而引起的。在这项研究中要检验的假设是，通过应用竞争性排除原则，可以减少储存污泥中e大肠杆菌的再生。即，通过大肠杆菌与快速生长的非致病细菌之间的竞争，将引入脱水的污泥。在食品行业，多年来，竞争性排斥原则已成功用作感染控制的一种手段。在这项研究中，我们旨在开发不同微生物群落组成的接种物，并评估其抑制大肠杆菌在消化污泥中生长的能力。目标1：测试竞争性排除概念以测试研究的基本前提，将设计一个受控且复制的台式实验，在该实验中，对污泥样品进行了消毒，然后与大肠杆菌和竞争性微生物重新接种。在本实验中，大肠杆菌将受到接种罪的挑战，这些接种物的竞争程度不同。在没有或有限竞争的情况下，大肠杆菌的人口会增加。大肠杆菌必须与一个多样化且适应良好的社区竞争可用资源的地方，我们预计人口增长会降低或缺席。目标2：一旦成功测试了竞争性排除概念，将优化竞争性排除概念，将优化竞争性排除产品。我们将研究：（i）挑战接种物的最佳来源是什么 - 例如，来自土壤或消化的蛋糕本身。 （ii）竞争人口需要多大？种子种群足以与大肠杆菌竞争吗？还是竞争性排除产品必须在能够竞争之前达到一定大小？ （iii）竞争性排除产品的微生物群落结构的关键特征有多重要。微生物群落结构的测量将通过磷脂脂肪酸（PLFA）表型分析进行。目标3：一旦根据基准量表进行了扩展，将使用试验尺度发酵罐来扩展文化工作。如果这项试点规模的工作的结果有望承诺，将有机会在联合公用事业设施进行全面试验。