In Vitro Mass-Screening of Lactic Acid Bacteria as Potential Biosorbents of Cesium and Strontium Ions

Abstract

Many radionuclides were scattered by the explosion at the Fukushima Daiichi Nuclear Power Station. We examined whether lactic acid bacteria (LAB) can sorb cesium ions (Cs+) and strontium ions (Sr2+) for radioprotection. Many strains showed biosorption to Cs+ and Sr2+ using an in vitro mass-screening although each strain showed different sorption. We selected MYU 111, MYU 758, and MYU 759 strains that showed especially high biosorption to Cs+ and/or Sr2+. MYU 111 was identified as Lactobacillus plantarum, and MYU 758 and 759 were Pediococcus pentosaceus. The selected strains tended to show higher biosorption when using the buffer method compared to the culture method. Further, they showed high biosorption at a low concentration of 1 ppb Cs+ and Sr2+ (max 28.8% and 97.7% sorption, respectively). This is the first study where lactic acid bacteria are shown to have biosorption of Cs+ and Sr2+.

Lactic acid bacterial exopolysaccharides strongly bind histamine and can potentially be used to remove histamine contamination in food

“…We previously reported that LAB strongly bind heavy metals, e.g. cadmium and mercury [12,13] as well as caesium and strontium [14] from human body. Some LAB strains are known to produce histamine from histidine during the ripening of cheese and wine [15].…”

Simultaneous removal of caesium and strontium using different removal mechanisms of probiotic bacteria

“…1 , Cs is most likely retained in bacteria by trapping in polyphosphate; however, this does not mean that other mechanisms are not involved. Some previously published studies have reported Cs biosorption by the surface components of bacteria 13 , 28 , 34 , 35 , and it is possible that the microorganisms used in this study also adsorbed Cs on the surface. Therefore, the adsorbed Cs + may have been replaced by the highly charged Sr 2+ and released.…”

“…Based on our results, it is plausible that Sr is removed by biosorption, which occurs independently of bacterial metabolism, as Sr removal occurred without a nutrient source. In previous reports, the mechanism of Sr removal using microorganisms was considered to be through biosorption occurring on the surface of bacteria 13 , 31 . In addition, our previous study suggested that L. casei JCM1134 removed Sr via adsorption 21 .…”