Ammonia-recycled percolation process for pretreatment of biomass feedstock |
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Authors: | Yoon H H Wu Z W Lee Y Y |
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Institution: | 1. National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, 100871, Beijing, China
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Abstract: | The construction of a gene encoding Lys-human proinsulin, its direct expression inE. coli, and the simple purification procedure are described here. The temperature inducible promotor was employed for induction in a very short time. The expression level could reach 20–30%. After simple downstream processing and only one step of Sephadex G50 purification, 150 mg recombinant Lys-human proinsulin with a purity of up to 90% could be obtained easily from 1L of high density fermentation medium. The obtained product is in the form of Met-Lys-human proinsulin because of the failure of the bacterial host to remove the initiator methionine residue. The Lys-human proinsulin could be changed into human insulin by trypsin and carboxypeptidase B treatment in later steps. After separation with DEAE-Sephadex A25, human insulin with expected amino acid composition and full native biological activity could be obtained with a yield of 50 mg/L of fermentation medium. |
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