Conventional and Innovative Hygienization of Feedstock for Biogas Production: Resistance of Indicator Bacteria to Thermal Pasteurization, Pulsed Electric Field Treatment, and Anaerobic Digestion

Abstract

Animal by-products (ABP) can be valorized via anaerobic digestion (AD) for biogas energy generation. The digestate issued from AD process is usually used to fertilize farming land for agricultural activities, which may cause potential sanitary risk to the environment. The European Union (EU) requires that certain ABP be thermally pasteurized in order to minimize this sanitary risk. This process is called hygienization, which can be replaced by alternative nonthermal technologies like pulsed electric field (PEF). In the present study, Enterococcus faecalis ATCC 19433 and Escherichia coli ATCC 25922 were used as indicator bacteria. Their resistance to thermal pasteurization and PEF treatment were characterized. Results show that Ent. faecalis and E. coli are reduced by 5 log10 in less than 1 min during thermal pasteurization at 70 °C. The critical electric field strength was estimated at 18 kV∙cm−1 for Ent. faecalis and 1 kV∙cm−1 for E. coli. “G+” bacteria Ent. faecalis are generally more resistant than “G-” bacteria E. coli. AD process also plays an important role in pathogens inactivation, whose performance depends on the microorganisms considered, digestion temperature, residence time, and type of feedstock. Thermophilic digestion is usually more efficient in pathogens removal than mesophilic digestion.

Occurrence and Multidrug Resistance in Strains of Listeria monocytogenes Recovered from the Anaerobic Co-Digestion Sludge Contained in a Single Stage Steel Biodigester: Implications for Antimicrobial Stewardship

“…Accordingly, microorganisms are grouped into thermophiles, mesophiles and psychrophiles depending on the temperature at which the organism thrives and operates. In relation to biogas technology (anaerobic digestion), several findings have shown that the thermophilic and mesophilic temperature ranges are well suited for efficient biogas production and pathogen inactivation [ 55 , 56 ]. However, mesophilic anaerobic digestion is preferred to the thermophilic process because the latter is vulnerable to increase in odour production and process instability, and requires extra power [ 57 ].…”

Kinetic study of thermal inactivation of enterococci and clostridial spores

“…À la fin de l'incubation, le dénombrement est effectué par la méthode NPP (nombre le plus probable) par lecture visuelle de la présence ou de l'absence de culot bactérien (Liu et al, 2021).…”

Challenges of pathogen inactivation in animal manure through anaerobic digestion: a short review

“…However, the resistance of pathogens causes obstacles to the effective inactivation of pathogens. In addition, it is reported that it’s more difficult to reduce pathogens for treatment on larger scales (e.g., full scale biogas plants) than that on laboratory scales [ 49 ]. Therefore, how to strengthen the inactivation of pathogens in practical engineering should be further discussed.…”