Anion Exchange chromatography is commonly used as the capture step in purification of acidic, recombinant proteins from E. coli fermentation extracts. When operated at basic pH, the target protein, as well as acidic E. coli proteins, negatively charged colored impurities, DNA, and endotoxin would be expected to bind. Treatment of the extract to remove these impurities prior to chromatography may lead to increased resin capacity for the target protein, and increased product quality due to decreased concentrations of these compounds in the product pools. Additionally, fouling of the resin over time by difficult to remove contaminants may be decreased by an effective pre-treatment of the feed stream. These considerations must be balanced against product loss, cost of raw materials, increase in cycle time, and ease of operation. We have developed an E. coli extract batch or column mode treatment procedure that employs Dowex 1x4-400. The yield of the target recombinant protein, MW 26 kDa, pI = 5.3, is greater than 95%. Endotoxin levels are reduced, and a range of colored impurities are removed; one of which is a putative catechol. Resin capacity was increased, and the product pool from the treated feed stream appeared purer by spectral analysis.