Effect of Different Processing Methods on the Number of Bacteria of the Genus Clostridium (Clostridia, Bacteria) in Animal By-Products

Clostridia are one of the largest genera of eubacteria inhabiting water, soil, human and animal intestine. The genus Clostridium includes both pathogenic and nonpathogenic species. The members of this genus occupy a leading position among all types of bacteria in producing diverse toxins. Due to the ability to form spores, these microorganisms are able to survive in the most unfavorable conditions. Antibiotic-resistant clostridia that are transferred into the environment in the manure of farm animals represent a special environmental hazard. In the present work, the effect of different methods of processing (aeration, acidification, addition of surfactants) the liquid fraction (LF) of pig manure effluents (MEs) on the species composition and number of clostridia was studied. It was established that Cl. septicum and Cl. perfringens occupy a dominant position in the MEs of manure accumulation baths. Both species are actively involved in the ammonification of organic compounds, releasing a wide spectrum of volatile substances with an unpleasant odor into the environment. The highest portion of clostridia was detected in biofilms forming on the surface of MEs under anaerobic conditions. Such conditions develop when LF is stored in covered lagoons, which increases the environmental risks of transferring undesirable microorganisms into the environment. A 24-h aeration and acidification of MEs to pH 5.5 contributed to a decrease in the number of clostridia. The appropriate conditions led to the formation of consortia of microorganisms, in which fungi occupied a dominant position. Cl. difficile (32.52%), Cl. putrificum (31.62%), and Cl. septicum (30.72%) dominated in the biofilms of acidified MEs; Cl. difficile (69.98–95.26%), in the variants with the addition of surfactants. The highest relative number of pathogenic Cl. difficile (95.26%) was observed in the variant with the addition of a cation-active surfactant (benzalkonium chloride).