Optimizing Biogenic Manganese Oxide Production

Abstract

The presence of emerging organic contaminants in surface and ground water sources poses challenges for traditional drinking water treatments such as granular activated carbon and ozonation with sand filtration. Manganese (Mn) oxides can oxidize several organic compounds and may provide another avenue for removal of these pollutants. While the biological impetus is not completely understood, certain microorganisms are capable of oxidizing soluble manganese to produce Mn oxides (e.g. MnO2). This study’s model manganese-oxidizing bacteria (MOB) are Bacillus sp. strain SG-1 and Pseudomonas putida MnB1. Bacillus sp., a marine bacterium, forms spores upon which manganese is oxidized and precipitates. P. putida, a freshwater bacterium, deposits the oxidized mineral on the outer cell membrane.

The cultures were grown in a liquid medium, with temperature and pH as experimental factors. The optical density (OD) of each culture was regularly measured during incubation in order to develop growth curves and determine the maximum specific growth rates. Maximum specific growth rate was used to calculate the doubling time during the exponential growth phase.

The results showed that the growth of the MOB is favorable at ambient temperatures and near neutral pH. The optimal conditions for the growth of Pseudomonas putida in Luria-Bertani broth were determined. The results also demonstrate that an alternative growth medium for Bacillus sp. SG-1 should be investigated. The results of this study provide insight for optimizing reactor conditions for the growth of MOB and production of Mn oxides, which is an important step toward their use in engineered systems.