Bacterial pathogens in output material from biogas plants processing livestock manure: A real threat?
Biogas plants represent currently an important part of agricultural production management. While the main feedstock for anaerobic digestion is corn and grass silage, they can be fed also with bio-waste materials, such as cattle, swine or poultry manure. Fugate, the waste product of biogas production, is regularly used in agriculture as fertiliser. But it can contain bacterial pathogens commonly related to animal husbandry. The aim of the study was (i) to compare different types of manure with regard to the content of selected zoonotic agents after anaerobic digestion process and (ii) examine the effect of a stage of treating fugate after anaerobic digestion. The numbers of coliform bacteria, Salmonella spp., Clostridium perfringens, Campylobacter spp. and total anaerobes were investigated by cultivation in fugate samples and evaluated as log CFU/g of a dry matter. Furthermore, a comparison of dendrograms based on partial 16S rRNA gene sequences was done. Our results showed that there were significant differences in numbers of all monitored groups of bacteria between samples from biogas plants processing different type of manure. The fugate from swine manure showed higher counts of Clostridium perfringens than those from poultry and cattle manure (by one and two order of magnitude respectively; P < 0,0001). The lowest numbers of pathogens were detected in fugate from cattle manure, with undetectable counts of coliforms after anaerobic digestion process (prior log CFU = 5). The study should help improve the hygiene of agricultural production and raise awareness of zoonotic infections originating from animal husbandry. Acknowledgments: This study was supported by the Ministry of Agriculture of the Czech Republic (Project No. MZeRO0719).
Vlčková Jana, Ing., Ph.D.
Marounek Milan, Prof. Ing., DrSc.
Skřivanová Věra, Prof. Ing., CSc.
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