Production and purification of high value recombinant proteins in plant agriculture offers the opportunity for lower cost therapeutics and/or the potential for multiple products from biomass processes (e.g., bioethanol facilities). In either case, because the product is generally at a low concentration after aqueous extraction, a large volume of feed would need to be processed. One promising operation is the use of membrane adsorbers in the place of packed adsorption columns. The advantages of membrane adsorption compared to a traditional packed bed of resin beads for the purification of protein products are well documented: membrane units are capable of higher throughput, operate at lower pressures, and can have elevated binding capacities (especially for high molecular weight targets being loaded at relatively high flow rates). As with resin-based chromatography, membrane adsorption can be operated in different modes. One option is to selectively bind the product molecule while impurities pass through without adsorbing. Elution conditions are then chosen to further purify the bound product from other adsorbed species. As an alternative, negative mode (or “flow through”) adsorption may be utilized. In this case, conditions are chosen to maximize binding of impurities while the product remains in solution and is collected at the outlet. Two crucial factors to consider when selecting the most appropriate mode of operation are: (1) binding capacity (breakthrough) of the product versus impurities, and (2) the ability to elute bound species in narrow peaks. As such, not only will the adsorption medium and operating conditions play a role in separation efficiency, but the properties of the target molecule and impurities will also have a major impact on performance. Here we present results evaluating the efficiency of purification (as quantified by yield, purity, processing time, and processing cost) for recovery of a target protein from both corn and soybean production hosts. The “bind and elute” method is compared to the “flow through” method for both membrane adsorption and packed bed adsorption, each operated to purify a low molecular weight product and a high molecular weight product.