Effect of postinduction nutrient feed composition and use of lactose as inducer during production of thermostable xylanase in Escherichia coli glucose-limited fed-batch cultivations

Ramchuran, S.O.; Holst, O.; Karlsson, E.Nordberg.

Journal of Bioscience and Bioengineering 99(5): 477-484

2005


ISSN/ISBN: 1389-1723
PMID: 16233820
DOI: 10.1263/jbb.99.477
Accession: 012001637

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Abstract
Escherichia coli is a microorganism routinely used in the production of heterologous proteins. The overexpression of a xylanase (Xyn10A Delta NC), which originated from the thermophile Rhodo-thermus marinus cloned under the control of the strong T7/lac promoter in a defined medium (mAT) using a substrate-limited feed strategy, was however shown to impose a significant metabolic burden on host cells. This resulted in a decreased cell growth rate and ultimately also a decreased target protein production. The investigation hence centers on the effect of some selected nutrient feed additives (amino acid [Cys] or TCA-intermediates [citrate, succinate, malate]) used to relieve the metabolic burden imposed during the feeding and postinduction phases of these glucose-limited fed-batch cultivations. The use of either succinic acid or malic acid as feed-additives resulted in an increase in production of approximately 40% of the heterologous thermostable xylanase. Furthermore, use of lactose as an alternative inducer of the T7/lac promoter was also proven to be a suitable strategy that significantly prolonged the heterologous protein production phase as compared with induction using isopropyl P-D-thiogalactopyranoside (IPTG).