Biotechnological production of amino acids and derivatives: current status and prospects.

For almost 50 years now, biotechnological production processes have been used for industrial production of amino acids. Market development has been particularly dynamic for the flavor-enhancer glutamate and the animal feed amino acids L: -lysine, L: -threonine, and L: -tryptophan, which are produced by fermentation processes using high-performance strains of Corynebacterium glutamicum and Escherichia coli from sugar sources such as molasses, sucrose, or glucose. But the market for amino acids in synthesis is also becoming increasingly important, with annual growth rates of 5-7%. The use of enzymes and whole cell biocatalysts has proven particularly valuable in production of both proteinogenic and nonproteinogenic L: -amino acids, D: -amino acids, and enantiomerically pure amino acid derivatives, which are of great interest as building blocks for active ingredients that are applied as pharmaceuticals, cosmetics, and agricultural products. Nutrition and health will continue to be the driving forces for exploiting the potential of microorganisms, and possibly also of suitable plants, to arrive at even more efficient processes for amino acid production.

Thiourea-based non-nucleoside inhibitors of HIV reverse transcriptase as bifunctional organocatalysts in the asymmetric Strecker synthesis.

The potential of novel and known pyridyl thiourea derivatives (non-nucleoside inhibitors (NNI) of HIV reverse transcriptase) as bifunctional organic catalysts in the asymmetric Strecker synthesis was investigated. It was shown that incorporation of the imidazolyl moiety in place of a pyridyl group results in a new thiourea derivative that displays a much higher catalytic activity.

The complete Corynebacterium glutamicum ATCC 13032 genome sequence and its impact on the production of L-aspartate-derived amino acids and vitamins.

The complete genomic sequence of Corynebacterium glutamicum ATCC 13032, well-known in industry for the production of amino acids, e.g. of L-glutamate and L-lysine was determined. The C. glutamicum genome was found to consist of a single circular chromosome comprising 3282708 base pairs. Several DNA regions of unusual composition were identified that were potentially acquired by horizontal gene transfer, e.g. a segment of DNA from C. diphtheriae and a prophage-containing region. After automated and manual annotation, 3002 protein-coding genes have been identified, and to 2489 of these, functions were assigned by homologies to known proteins. These analyses confirm the taxonomic position of C. glutamicum as related to Mycobacteria and show a broad metabolic diversity as expected for a bacterium living in the soil. As an example for biotechnological application the complete genome sequence was used to reconstruct the metabolic flow of carbon into a number of industrially important products derived from the amino acid L-aspartate.

Rapid evaluation of oxygen and water permeation through microplate sealing tapes.

Eight commercially available microplate sealing tapes and 10 other suitable materials (transparent wound dressings) are compared qualitatively in terms of their ability to minimize water evaporation from a multiwell plate while maintaining the oxygen supply as high as possible, which is necessary for applications like aerobic growth. The transparency and sterility of the products are considered as well. All evaluated commercially available sealing tapes fall into one of the following two classes: (1) O(2) transfer is comparable to that of an unsealed plate, but water vapor retention is relatively low, or (2) O(2) transfer via the sealing is slower, but the water retention capability is comparably high. All but one of the evaluated wound dressings fall under the second class. That dressing, however, constitutes a compromise by showing both moderate O(2) permeability and medium water retention. But the estimated mass transport in a microtiter plate sealed with this dressing is about 5 times slower than that of an unsealed 96 well plate. The aim of this publication is to enable the reader to choose a microtiter plate sealing from the materials evaluated within this work and to use the rapid methods described herein to easily perform tests of additional sealing materials.

Strategy to sequence the genome of Corynebacterium glutamicum ATCC 13032: use of a cosmid and a bacterial artificial chromosome library.

The initial strategy of the Corynebacterium glutamicum genome project was to sequence overlapping inserts of an ordered cosmid library. High-density colony grids of approximately 28 genome equivalents were used for the identification of overlapping clones by Southern hybridization. Altogether 18 contiguous genomic segments comprising 95 overlapping cosmids were assembled. Systematic shotgun sequencing of the assembled cosmid set revealed that only 2.84 Mb (86.6%) of the C. glutamicum genome were represented by the cosmid library. To obtain a complete genome coverage, a bacterial artificial chromosome (BAC) library of the C. glutamicum chromosome was constructed in pBeloBAC11 and used for genome mapping. The BAC library consists of 3168 BACs and represents a theoretical 63-fold coverage of the C. glutamicum genome (3.28 Mb). Southern screening of 2304 BAC clones with PCR-amplified chromosomal markers and subsequent insert terminal sequencing allowed the identification of 119 BACs covering the entire chromosome of C. glutamicum. The minimal set representing a 100% genome coverage contains 44 unique BAC clones with an average overlap of 22 kb. A total of 21 BACs represented linking clones between previously sequenced cosmid contigs and provided a valuable tool for completing the genome sequence of C. glutamicum.