Inactivation of Human Pathogens during Phase II Composting of Manure-Based Mushroom Growth Substrate

Abstract

Commercial production of white button mushrooms (Agaricus bisporus) requires a specialized growth substrate prepared from composted agricultural by-products. Because horse and poultry manures are widely used in substrate formulations, there is a need to determine the extent to which the composting process is capable of eliminating human pathogens. In this study, partially composted substrate was inoculated with a pathogen cocktail (log 10⁶ to 10⁸ CFU/g) containing Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella. Pathogen and indicator-organism reductions were followed at temperatures that typically occurred during a standard 6-day phase II pasteurization and conditioning procedure. Controlled-temperature water bath studies at 48.8, 54.4, and 60°C demonstrated complete destruction of the three pathogens after 36.0, 8.0, and 0.5 h, respectively. Destruction of L. monocytogenes and E. coli O157:H7 at 54.4°C occurred more slowly than E. coli, total coliforms, Enterobacteriaceae, and Salmonella. Microbial reductions that occurred during a standard 6-day phase II pasteurization and conditioning treatment were studied in a small-scale mushroom production research facility. After phase II composting, E. coli, coliforms, and Enterobacteriaceae were below detectable levels, and inoculated pathogens were not detected by direct plating or by enrichment. The results of this study show that a phase II composting process can be an effective control measure for eliminating risks associated with the use of composted animal manures during mushroom production. Growers are encouraged to validate and verify their own composting processes through periodic microbial testing for pathogens and to conduct studies to assure uniform distribution of substrate temperatures during phase II.

Diversity ofListeria monocytogenesstrains isolated fromAgaricus bisporusmushroom production

“…Actions already in place to reduce cross‐contamination are, for example, the regular use of sanitizers and heat treatments at the end of the crop harvest (LaBorde ), plus the pasteurization of the substrate prior to delivery to the production facility (Weil et al . ). Additionally, advice on improving hygiene practices is available (Dzingirayi and Korsten ) and the utilization of novel technologies, like bacteriocins and bacteriophages alone or in addition to other sanitation procedures (Iacumin et al .…”

Inhibition ofListeria monocytogenesbiofilms by bacteriocin-producing bacteria isolated from mushroom substrate

“…Listeria monocytogenes has been shown to be present in the mushroom production environment (Viswanath et al 2013;Chen et al 2014;Murugesan et al 2015). The mushroom production chain is ideal for the occurrence of L. monocytogenes as it involves a range of growth substrates and environments that are conducive to its occurrence (Weil et al 2013). The substrate used for mushroom cultivation consists of a mixture of straw, bedded horse manure, wheat straw, chicken manure and gypsum, prepared by a three-phase composting process, involving uncontrolled self-heating (up to 80°C) for 1-2 weeks, followed by maintaining the compost at 40-58°C for 6 days, before being transported to the growing houses.…”

Optimization of watermelon waste as a bulking agent for sustainable co-composting of livestock manures using response surface methodology

“…Studies done on the co-composting of HM and CM as well as its impacts on physicochemical properties are scarce. Previously, CM and HM were co-composted using various types of green waste, sugar beet, and grape pomace as the bulking agent (Renčo et al, 2011;Weil et al, 2013;Liu Y. et al, 2018). However, studies on variations in physicochemical properties were only mentioned by Liu Y. et al (2018).…”