A biotechnological process for the removal of heavy metals from aqueous solution utilizes enzymatically liberated phosphate ligand which precipitates with heavy metals (M) as cell’bound MHPO4. The enzyme, a phosphatase, obeys Michaelis’Menten kinetics in resting and immobilized cells; an integrated form of the Michaelis’Menten equation was used to calculate the apparent Km (Km app.) as operating in immobilized cells in flow’through columns by a ratio method based on the use of two enzyme loadings (Eo1, Eo2) or two input substrate concentrations (So1, So2). The calculated Km app. (4.08 mM) was substituted into an equation to describe the removal of metals by immobilized cells. In operation the activity of the bioreactor was in accordance with that predicted mathematically, within 10%. The initial tests were done at neutral pH, whereas the pH of industrial wastewaters is often low; an increase in the Km app. at low pH was found in previous studies. Immobilized cells were challenged with acidic mine drainage wastewaters, where the limiting factors were chemical and not biochemical. Bioreactors initially lost activity in this water, but recovered to remove uranyl ion with more than 70% efficiency under steady’state conditions in the presence of competing cations and anions. Possible reasons for the bioreactor recovery are chemical crystallization factors.
Citation: Fernando I. RamÃrez-Paredes, Teresa Manzano-MuÃ±oz, Juan C. Garcia-Prieto, Galina G. Zhadan, Valery L. Shnyrov, John F. Kennedy and Manuel G. Roig, Biosorption of heavy metals from acid mine drainage onto biopolymers (chitin and Î± (1,3) Î²-D-glucan) from industrial biowaste exhausted brewer’s yeasts (Saccharomyces cerevisiae L.), Biotechnology and Bioprocess Engineering,16, 6, (1262)
This is an old paper from mid 90’s that gives us an insight on how heavy metals are removed from wastewater by immobilized cells. I found this paper interesting because it explained the chemistry of enzymes secreted by microbes pretty well.