Biocidal activity of fast pyroloysis biochar against E.coli 0157:H7 in soil varies based on production temperature or age of biochar

Authors: Gurtler, Joshua; Mullen, Charles; Boateng, Akwasi; MASEK, ONDREJ - University Of Edinburgh; Camp, Mary

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2020
Publication Date: 5/21/2020
Citation: Gurtler, J., Mullen, C.A., Boateng, A.A., Masek, O., Camp, M.J. 2020. Biocidal activity of fast pyroloysis biochar against E.coli 0157:H7 in soil varies based on production temperature or age of biochar. Journal of Food Protection. 83:1020-1029.

Interpretive Summary: Fresh produce-growing soils sometimes becomes contaminated with foodborne pathogenic bacteria and fields must be abandoned to prevent crops from become contaminated. Biochar, a black carbonaceous byproduct of pyrolysis, has been shown to kill pathogenic bacteria in soil. In this experiment, we tested biochar generated at temperatures of 450, 500 and 600 degrees Celsius to determine if it could kill E. coli O157:H7 in soils at lower concentrations than were previously tested. We demonstrated that the 600 degree biochar, but not the 450 or 500 degree biochars, was capable of inactivating this pathogen in soil at concentrations as low as 3 percent.

Technical Abstract: Fresh produce-growing soils, which become contaminated with foodborne pathogens, are sometimes abandoned/removed from production. The application of biochar has been proposed for bioremediating such pathogen-contaminated soils. The objectives of the present study were to utilize three in-house fast-pyrolysis-generated biochars (FPBC) (pyrolyzed at 450, 500 and 600 degrees Celsius in a newly-designed pyrolysis reactor) and ten United Kingdom Biochar Research Center (UKBRC) standard slow-pyrolysis biochars to determine their effects on the viability of four surrogate strains of E. coli O157:H7 in soil. Additionally, a previously biocidal fast-pyrolysis biochar was aged two years and tested against E. coli to determine if there was a difference in antibacterial efficacy over time. While neither the UKBRC slow-pyrolysis biochars or the 450 and 500 degree Celsius FPBC from the new reactor proved antimicrobial, the 600 degree Celsius biochar proved biocidal over 7 weeks of sampling (P < 0.05) with populations significantly reduced at the 3 and 3.5 percent concentration (5.34 and 5.84 log CFU/g, respectively) compared with concentrations of 0.0-2.0 percent. The aged 500 degree Celsius biochar from the older reactor, previously shown to be antimicrobial, demonstrated a loss of efficacy after aging for two years. These results demonstrate that the biocidal nature of FPBC varies based on production temperature and/or age of biochar.