TY - JOUR
T1 - High-level biosynthesis of norleucine in E. coli for the economic labeling of proteins
AU - Anderhuber, Niklaus
AU - Fladischer, Patrik
AU - Gruber-Khadjawi, Mandana
AU - Mairhofer, Juergen
AU - Striedner, Gerald
AU - Wiltschi, Birgit
PY - 2016/10/10
Y1 - 2016/10/10
N2 - The residue-specific labeling of proteins with non-canonical amino acids (ncAA) is well established in shake flask cultures. A key aspect for the transfer of the methodology to larger scales for biotechnological applications is the cost of the supplemented ncAAs. Therefore, we established a scalable bioprocess using an engineered host strain for the biosynthesis of the methionine analog norleucine at titers appropriate for the efficient and economic labeling of proteins. To enhance the biosynthesis of norleucine, which is a side-product of the branched chain amino acid pathway, we deleted all three acetolactate synthase isoforms of the methionine auxotrophic Escherichia coli expression strain B834(DE3). Additionally, we overexpressed leuABCD to boost the biosynthesis of norleucine. We systematically analyzed the production of norleucine under the conditions for its residue-specific incorporation in bioreactor cultures that had a 30-fold higher cell density than shake flask cultures. Under optimized conditions, 5 g/L norleucine was biosynthesized. This titer is two times higher than the standard supplementation with norleucine of a culture with comparable cell density. We expect that our metabolically engineered strain for the improved biosynthesis of norleucine in combination with the proposed bioprocess will facilitate the efficient residue-specific labeling of proteins at a reasonable price in scales beyond the shake flask.
AB - The residue-specific labeling of proteins with non-canonical amino acids (ncAA) is well established in shake flask cultures. A key aspect for the transfer of the methodology to larger scales for biotechnological applications is the cost of the supplemented ncAAs. Therefore, we established a scalable bioprocess using an engineered host strain for the biosynthesis of the methionine analog norleucine at titers appropriate for the efficient and economic labeling of proteins. To enhance the biosynthesis of norleucine, which is a side-product of the branched chain amino acid pathway, we deleted all three acetolactate synthase isoforms of the methionine auxotrophic Escherichia coli expression strain B834(DE3). Additionally, we overexpressed leuABCD to boost the biosynthesis of norleucine. We systematically analyzed the production of norleucine under the conditions for its residue-specific incorporation in bioreactor cultures that had a 30-fold higher cell density than shake flask cultures. Under optimized conditions, 5 g/L norleucine was biosynthesized. This titer is two times higher than the standard supplementation with norleucine of a culture with comparable cell density. We expect that our metabolically engineered strain for the improved biosynthesis of norleucine in combination with the proposed bioprocess will facilitate the efficient residue-specific labeling of proteins at a reasonable price in scales beyond the shake flask.
KW - Acetolactate synthase
KW - Bioreactor
KW - Biosynthesis
KW - Deletion
KW - Non-canonical amino acid
KW - Norleucine
UR - http://www.scopus.com/inward/record.url?scp=85013827016&partnerID=8YFLogxK
U2 - 10.1016/j.jbiotec.2016.04.033
DO - 10.1016/j.jbiotec.2016.04.033
M3 - Article
C2 - 27107466
AN - SCOPUS:85013827016
SN - 0168-1656
VL - 235
SP - 100
EP - 111
JO - Journal of Biotechnology
JF - Journal of Biotechnology
ER -