The isolation and identification of chlorate-reducing bacteria in milk

Chlorate has become a residue of concern in the food and beverage sector, related to the use of chlorine sanitizers in industrial food production and water treatment, and is of particular concern to regulatory bodies due to the negative health effects associated with chlorate exposure. This study investigated the fate of chlorate in raw milk and isolated bacterial strains of interest responsible for chlorate breakdown. Milk, if left unpasteurised was found to reach undetectable chlorate levels in 11 days when enriched to 100 µg l-1. Further enrichment and isolation using conditions specific to chlorate reducing bacteria successfully isolated 5 distinct strains of Hafnia paralvei. Chlorate-reducing bacteria were observed to grow in media enriched with lactate as an electron acceptor, with no growth observed when using citrate. All isolates were demonstrated to reduce chlorate in liquid media, but no genes associated with chlorate-mediated respiration were detected in whole genome sequencing data.