Toxoflavin contamination in rice samples from rice processing complexes in South Korea

Toxoflavin contamination was investigated in broken rice produced as a by-product of domestic rice processing complexes (RPCs) in 2011 in South Korea. Of the 68 RPCs investigated, toxoflavin contamination was confirmed in 12 from three provinces: Gangwon, Gyeonggi, and Gyeongsang. Isolation of toxoflavin-producing bacteria independent of toxoflavin contamination was also performed in this study. We obtained 25 toxoflavin-producing bacterial isolates from rice samples; these samples were collected from the same 12 RPCs mentioned above. All 25 toxoflavin-producing bacteria were identified as Burkholderia glumae by 16S rRNA gene sequencing. Toxoflavin-producing ability differed slightly among the 25 isolates, but they all inhibited rice seed germination and induced seed rot. This is the first report of toxoflavin contamination and the toxin-producing bacterium B. glumae in broken rice produced during the rice milling process. Because toxoflavin has stable physical properties even above a boiling temperature of 100°C, it can pose a problem even if rice is cooked or processed. These results will serve as baseline data aiding comprehensive management of toxoflavin contamination during the post-harvest storage and processing of rice.