Coping with complexity in metabolic engineering.

In the past decade, systems biology has revealed great metabolic and regulatory complexity even in seemingly simple microbial systems. Metabolic engineering aims to control this complexity in order to establish sustainable and economically viable production routes for valuable chemicals. Recent advances in systems-level data generation and modeling of cellular metabolism and regulation together with tremendous progress in synthetic biology will provide the tools to put biotechnologists on the fast track for implementing novel production processes. Great potential lies in the reduction of cellular complexity by orthogonalization of metabolic modules. Here, we review recent advances that will eventually enable metabolic engineers to predict, design, and build streamlined microbial cell factories with reduced time and effort.

Updating the metagenomics toolbox.

Metagenomics--the application of the genomics suit of technologies to uncultivated microorganisms--is coming of age. Sophisticated technologies are being developed and adapted to this promising genetic resource to make increasing use of the seemingly boundless molecular and functional diversity. Particular progress has been made in the areas of randomly proliferating limited-source DNA, massively parallel sequencing without cloning, isolating specific target sequences from highly complex template mixtures, high-throughput assay systems targeting metabolic pathways, artificial transcriptional regulators activating reporter genes to indicate enzymatic substrate conversion and cDNA cloning from extracted mRNA to directly clone actively expressed genes from a microbial consortium. However, challenges still lie ahead. Most prominently, the efficient heterologous expression of a plethora of potentially interesting enzymes from unknown source organisms is not readily achieved.

Biocatalytic deuterium- and hydrogen-transfer using over-expressed ADH-'A': enhanced stereoselectivity and 2H-labeled chiral alcohols.

Employing the over-expressed highly organic solvent tolerant alcohol dehydrogenase ADH-'A' from Rhodococcus ruber DSM 44541, versatile building blocks, which were not accessible by the wild type catalyst, were obtained in > 99% e.e.; furthermore, employing d8-2-propanol as deuterium source, stereoselective biocatalytic deuterium transfer was made feasible to furnish enantiopure deuterium labeled sec-alcohols on a preparative scale employing a single enzyme.