Arsenic removal by native and chemically modified lactic acid bacteria

Arsenic in drinking water is a major health problem globally. Simple, novel methods are needed for its removal from water, especially in rural areas. For this purpose, the potential of different microbes in toxin and heavy metal removal from water has gained interest. This study focused on the arsenic removal capacity of three Lactobacillus strains in their native and chemically modified forms. Both native and methylated forms of all three strains were not efficient in arsenic removal. Aminated Lactobacillus casei DSM20011 was observed to remove As(V) but not As(III) in water. Removal was fast, dependent on pH and As(V) concentration. The highest removal percentage 38.1 ± 9.0% was observed at the lowest As(V) concentration (100 μg/l) studied at pH 7. The maximum As(V) removal capacity, calculated from Langmuir isotherm, was 312 ± 68 μg As(V)/g dry biomass. Interactions between As(V) and the bacteria were weak, demonstrated by release of removed As(V) when contact time was prolonged. Desorption with 1.5 mM HNO3 and NaOH released all bound As(V) indicating that removal occurred at the bacterial surface.