PROCESS AND ECONOMIC-EVALUATION OF THE EXTRACTION AND PURIFICATION OFRECOMBINANT BETA-GLUCURONIDASE FROM TRANSGENIC CORN

A process model for the recovery and purification of recombinant beta- glucuronidase (rGUS) from transgenic corn was developed, and the proce ss economics were estimated. The base-case bioprocessing plant operate s 7500 h/year processing 1.74 million (MM) kg of transgenic corn conta ining 0.015% (db) rGUS. The process consists of milling the corn into flour, extraction of protein by using 50 mM sodium phosphate buffer, a nd rGUS purification by ion exchange and hydrophobic interaction chrom atography. About 137 kg of rGUS of 83% (db) purity can be produced ann ually. The production cost amounted to $43000/kg of rGUS. The cost of milling, protein extraction, and rGUS purification accounted for 6, 40 , and 48% of annual operating cost, respectively. The cost of transgen ic corn was 31% of the raw material costs or 6% of the annual operatin g cost. About 78% of the cost of buffer and water were incurred in the protein extraction section, while 88% of other consumables were from the purification section. The sensitivity analysis indicated that rGUS can be produced profitably from corn even at the 0.015% (db) expressi on lever, assuming a selling price of $100000/kg GUS. An increase in r GUS expression levels up to 0.08% significantly improves the process e conomics.