bioengineering Article Impact of Glycerol as Carbon Source onto Specific Sugar and Inducer Uptake Rates and Inclusion Body Productivity in E. coli BL21(DE3) Julian Kopp 1, Christoph Slouka 1, Sophia Ulonska 2, Julian Kager 2, Jens Fricke 1, Oliver Spadiut 2 and Christoph Herwig 1,2,* ID 1 Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Institute of Chemical, Environmental and Biological Engineering, Vienna University of Technology, 1060 Vienna, Austria;
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[email protected]; Tel.: +43-(1)-58801-166084 Academic Editor: Mark Blenner Received: 24 October 2017; Accepted: 19 December 2017; Published: 21 December 2017 Abstract: The Gram-negative bacterium E. coli is the host of choice for a multitude of used recombinant proteins. Generally, cultivation is easy, media are cheap, and a high product titer can be obtained. However, harsh induction procedures using isopropyl β-D-1 thiogalactopyranoside as inducer are often referred to cause stress reactions, leading to a phenomenon known as “metabolic” or “product burden”. These high expressions of recombinant proteins mainly result in decreased growth rates and cell lysis at elevated induction times. Therefore, approaches tend to use “soft” or “tunable” induction with lactose and reduce the stress level of the production host.