Human glucagon-like peptide-1 (GLP-1), an incretin hormone with pharmaceutical potential in treating type 2 diabetes mellitus is known to be rapidly degraded when expressed in Escherichia coil. For the efficient production of the intact GLP-1 using a recombinant E. coil system, a fusion protein of GLP-1 was designed to be composed of the 6-lysine tag, ubiquitin and GLP-1 (K6UbGLP-1) in a row. A fed-batch fermentation of recombinant E. coil BL21(DE3)/pAPK6UbGLP-1 was carried out in a pH-stat feeding strategy and resulted in 11.3 g/L of K6UbGLP-1 as a form of inclusion body. Solid-phase refolding of K6UbGLP-1 inclusion body using a cation exchanger of the SP Sepharose FF led to a refolding yield over 90% even at 5.2 mg protein/mL resin. On-column cleavage of the refolded K6UbGLP-1 with ubiquitin-specific protease 1 gave an authentic form of GLP-1. Instrumental analyses using mass spectrometry and reverse-phase HPLC showed that the recombinant GLP-1 released from K6UbGLP-1 was identical to the standard GLP-1. (C) 2011 Elsevier Inc. All rights reserved.