Mini-scale cultivation method enables expeditious plasmid production in Escherichia coli

• Published in: Biotechnology journal 2014-01, Vol.9 (1), p.128-136
• Main Authors: Grunzel, Petra, Pilarek, Maciej, Steinbrück, Dörte, Neubauer, Antje, Brand, Eva, Kumke, Michael U., Neubauer, Peter, Krause, Mirja
• Format: Article
• Language: English
• Subjects: Bioreactors; Biotechnology - instrumentation; Biotechnology - methods; Escherichia coli; Escherichia coli - genetics; Escherichia coli - growth & development; Fermentation; High-cell-density culture; Industrial Microbiology; Miniaturized cultivations; Optical oxygen sensor; Oxygen - metabolism; Plasmid DNA production; Plasmids - metabolism; Spectrophotometry
• ISSN: 1860-6768; 1860-7314
• DOI: 10.1002/biot.201300177

The standard procedure in the lab for plasmid isolation usually involves a 2‐mL, 16 h over‐night cultivation in 15‐mL bioreaction tubes in LB medium. This is time consuming, and not suitable for high‐throughput applications. This study shows that it is possible to produce plasmid DNA (pDNA) in a 1.5‐mL microcentrifuge tube with only 100 μL cultivation volume in less than 7 h with a simple protocol. Compared with the standard LB cultivation for pDNA production reaching a final pDNA concentration range of 1.5–4 μg mL–1, a 6‐ to 10‐fold increase in plasmid concentration (from 10 up to 25 μg mL–1 cultivation volume) is achieved using an optimized medium with an internal substrate delivery system (EnBase®). Different strains, plasmids, and the applicability of different inoculation tools (i.e. different starting ODs) were compared, demonstrating the robustness of the system. Additionally, dissolved oxygen was monitored in real time online, indicating that under optimized conditions oxygen limitation can be avoided. We developed a simple protocol with a significantly decreased procedure time, enabling simultaneous handling of more samples, while a consistent quality and a higher final pDNA concentration are ensured. Simple and fast plasmid preparation is a crucial step in the study of genes and their functions. In this article, the authors describe an efficient plasmid preparation protocol in microliter scale. While the procedures currently in standard use require overnight incubation of a 2 mL sample volume, this optimized procedure requires only 6 hours of incubation and a 100 μL sample volume. This efficient protocol could be both implemented in the molecular biology laboratory and employed in automated high‐throughput applications.