In this issue: Biotechnology Journal 3/2010

Metabolic engineering for industrial applications Nielsen et al., Biotechnol. J. 2009, 5, 274–284 With a carbon chain length of four and two reactive sites, 2,3‐butanediol (2,3‐BD) is a versatile building block molecule for the synthesis of both fine and commodity chemicals for use as drugs, cosmetics or liquid fuels. Diacetyl and acetoin have important applications in the food, beverage and fragrance industries. Kristala Jones‐Prather and colleagues from the MIT (Cambridge, MA, USA) designed new strains of Escherichia coli that are able to produce acetoin together with small amounts of 2,3‐BD. They first designed the metabolic pathways and screened for enzymes of yeast and bacterial origin to perform it. Those have been introduced in E. coli , while bypaths that reduce the yield of target molecules were disrupted. This approach of metabolic engineering is a promising strategy for strain development for many other chemicals Yoghurt Lactobacilli synthesize nanoparticles Jha and Prasad et al., Biotechnol. J. 2009, 5, 285–291 Bacteria have the natural property to reduce and oxidize metal ions into metallic and oxide nanoparticles, thereby functioning as “mini” nanofactories. Non‐pathogenic, gram positive, and mesophilic facultative anaerobe Lactobacilli commonly used for fermentation of milk were already shown to produce several metal and oxide nanoparticles. Researchers from Bhagalpur, India, now used bacteria from yoghurt and readily available pharmaceutical grade L. sporogens tablets for the transformation and synthesis of metallic silver (Ag) and titanium oxide (TiO 2 ) nanoparticles. The synthesis was performed at room temperature. Individual nanoparticles having the dimensions of 10–25 nm (n‐Ag) and 10–70 nm (n‐TiO 2 ) were detected. Liver cell drug toxicity model Laurent et al., Biotechnol. J. 2009, 5, 314–320 Differentiated hepatocytes are a valuable model to study metabolic processes and toxicity of chemotherapeutic drugs. Primary human hepatocytes and hepatoma cell lines have only limited availability or contain only low activity of cytochrome P450 enzymes (CYPs) which are important to study drug metabolism. HepaRG progenitor cells are capable of differentiating into hepatocyte‐like cells that express a large set of liver‐specific functions. They express only small amounts of CYPs, which limits their use for toxicological studies of drugs metabolized by this pathway. Authors from Rennes, France establish an efficient transfection protocol to increase transient CYP2E1 expression in progenitors and/or differentiated HepaRG cells by electroporation. This newly generated cell line opens now a new perspective for CYP‐dependent drug metabolism and toxicity studies using HepaRG cells.