M(III)-facilitated recovery and concentration of enzymes from mesophilic and thermophilic organisms

Six enzymes isolated from organisms of widely differing thermal growth optima were flocculated from solution at constant pH by addition of Fe(III) solution. In all cases the enzyme concentration was 1 g.l-1 or less. Flocculation profiles were generated for each enzyme over a range of Fe(III) levels. The concentrated enzymes were recovered from the Fe(III)/protein complex by solubilisation with citrate and dithionite followed by precipitation with ammonium sulphate. In all cases approximately 70-80% enzyme recovery was achieved. Enzyme thermal stability did not appear to be important and protein concentration had no effect on the efficiency of enzyme recovery over the range of 0.01-1 g.l-1. Approximately 30 mmol Fe(III)/l of enzyme solution facilitated optimal enzyme recovery for all solutions studied. For protein concentrations up to 1 g.l-1 a 100-fold enzyme concentration factor can be expected.