Western diet is frequently low in essential metal ions. A common method for preventing metal ion deficiency is pharmacological supplementation, especially in a highly available form such as metalo-protein complexes. Accordingly, in this work, specific lactic acid bacteria were assessed for their ability to bind copper ions. Significant amounts of copper ions were bound, and the binding potential was found to be strain specific. Differences among the strains were evaluated with the Langmuir model for biosorption. Binding of copper was a fast process, strongly influenced by ionic strength, pH and biomass concentration. During the process, copper ions significantly reduced cell viability. Discharge of copper ions in a simulated gastrointestinal tract was examined; 85-90% of copper ions bound to LAB were discharged in the gastrointestinal model system.
The safety of two probiotic bifidobacterial strains, Bifidobacterium breve M-16V and Bifidobacterium infantis M-63, was evaluated by single dose and 90-day repeated dose oral toxicity tests using rats. In the single dose oral toxicity test using 1.4 × 1012 CFU/kg of B. breve M-16V or 3.2 × 1011 CFU/kg of B. infantis M-63, there were no death and no abnormalities. In the 90-day repeated dose oral toxicity test using 2.3 × 1011 CFU/kg/day of B. breve M-16V or 7.6 × 1010 CFU/kg/day of B. infantis M-63, no death and no abnormalities in body weight, food consumption, water consumption, urinalysis, hematology, blood biochemistry, organ weights, and histophathological findings were observed. The acceptable daily intake (ADI) of B. breve M-16V was calculated to be 1.38 × 1011 CFU/day for an adult weighing 60 kg and 1.15 × 1010 CFU/day for an infant weighing 5,000 g. Based on the findings of the present study together with the taxonomy and distribution data, as well as clinical experience in preterm infants, B. breve M-16V may be considered as extremely safe for consumption by humans including infants. Although B. infantis M-63 was considered as safe as B. breve M-16V, further confirmation by clinical investigations may be required.
Hydrogen-utilizing bacteria in the feces of Japanese individuals were analyzed with the specific polymerase chain reaction targeting the functional genes. The formyltetrahydrofolate synthetase gene derived from acetogenic bacteria was predominantly detected in all subjects. We consider that reductive acetogenesis might be an important H2 disposal pathway in healthy Japanese.