Effect of metals on growth and functionality of Lactobacillus and Bifidobacteria

Evidence is mounting that certain metal ions in the intestinal environment are important in optimizing the growth and functionality of desirable bacterial strains used to formulate probiotic foods. It has been found that Fe 2+, Ca2+, and Al3+ each play a role in correcting growth inhibitions of other metals. In addition, various metals such as Fe2+, Ca2+, Zn2+, Cu2+, and Mn2+ affect the bacterial uptake of one another, some positively and others negatively. In addition to synergistic affects, there is still a debate about whether or not it is iron or manganese that is the required metal for many species of probiotic bacteria. Further, there are also conflicting studies on whether or not copper is inhibitory or activating. It has also been shown that certain metals such as Ca2+, Mn2+, and Fe2+ may play a major role in the activity of enzymes such as α- and β-galactosidases. This review discusses such studies and concludes that many of the effects of metals on probiotic bacteria are strain-specific. Effects may also depend on other characteristics such as pH, the salt in which ions are carried, and the composition of other metals, carbohydrates, and lipids in the surroundings.