Representative and valid cytoplasmic concentrations are essential for ensuring the significance of results in the field of metabolome analysis. One of the most crucial points in this respect is the sampling itself. A rapid and sudden stopping of the metabolism on a timescale that is much faster than the conversion rates of investigated metabolites is worthwhile. This can be achieved by applying of cold methanol quenching combined with reproducible, fast, and automated sampling. Unfortunately, quenching the metabolism by a sharp temperature shift leads to what is known as cold shock or the cell-leakage effect. In the present work, we applied a microstructure heat exchanger to analyze the cold shock effect using Corynebacterium glutamicum as a model microorganism. Using this apparatus together with a silicon pipe, it was possible to assay the leakage effect on a timescale starting at 1 s after cooling cell suspension. The high turnover rates not only require a rapid quenching technique, but also the correct application. Moreover, we succeeded in showing that even when the required appropriate setup of methanol quenching is not used, the metabolism is not stopped within the required timescale. By applying robust techniques like rapid sampling in combination with reproducible sample processing, we ensured fast and reliable metabolic inactivation during all steps.

Cereal Chem. 86(4):372-375The mechanical and viscoelastic properties of intact wheat kernels of 36 wheat cultivars differing in low molecular weight glutenin subunit (LMW-GS) composition (loci Glu-A3, Glu-B3, and Glu-D3) were evaluated using load-compression tests. Comparison among genotypic groups representing Glu-3 allelic variants showed that groups representing the alleles Glu-A3 b, c, and d; Glu-B3 d, g, and h; and Glu-D3 a, b, and d, had harder kernel texture, higher kernel elastic work and larger gluten strength-related parameters than those possessing alleles Glu-A3 e; Glu-B3 f, i and j (translocation 1B/1R); and Glu-D3 d. Modulus of elasticity (stress to strain ratio) showed low values (111.9-168.8 MPa) for allelic groups possessing poor elastic properties (Glu-A3 e; Glu-B3 f, i, and j; and Glu-D3 d), and high values (179.8-222.6 MPa) for allelic groups possessing high kernel elastic properties (Glu-A3 b c, and d; Glu-B3 d, g, and h; and Glu-D3 a, b and c). The highest values for gluten strengthrelated parameters (SDS-sedimentation, dough mixing time, and dough strength [W]) corresponded to allelic groups Glu-A3 d; Glu-B3 d and g; and Glu-D3 d, while the lowest corresponded to Glu-A3 e and Glu-B3 j. No significant differences were observed among groups with regard to gluten extensibility parameters; however, the highest P/L value (least extensibility) corresponded to Glu-B3 j, which indicates presence of 1B/1R translocation. Except for the Glu-B3 j (translocation 1B/1R) allele, which presented more variation within samples, a general relationship between kernel viscoelastic properties and dough viscoelastic properties was observed; samples showing higher elastic work to plastic work ratio (E/P) tended to possess better gluten strength than cultivars with low E/P ratio.

High and low molecular weight glutenin subunits (HMW‐GS and LMW‐GS, respectively) are the main factors determining the viscoelastic properties of wheat dough. The mechanical and viscoelastic properties of 29 samples of wheat kernels differing in HMW‐GS were evaluated with load‐compression tests. Samples were grouped by genotypes differing in HMW‐GS composition (allelic variants: Glu‐A1: null, 1, 2*; Glu‐B1: 7, 7+8, 7+9, 13+16, and 17+18; Glu‐D1: 5+10, 2+12). Groups representing Glu‐A1 1 and 2*; Glu‐B1 7, 7+9 and 17+18; and Glu‐D1 5+10 generally possessed hard grain and showed the largest kernel elasticity values, while those representing subunits Glu‐A1 null; Glu‐B1 7+8; and Glu‐D1 2+12 had soft kernels and showed lower elastic work values. Genotypes possessing HMW‐GS 1, 17+18 and 5+10 gave large SDS‐sedimentation values and better dough viscoelastic properties than those with allelels: null, 7+8, and 2+12. Kernel hardness showed significant correlation with the dough‐strength‐related parameters: SDS‐sedimentation; dough mixing time; and the alveographic parameters, W and P. There was a negative correlation between kernel plastic work and dough mixing time and the dough tenacity/extensibility parameters, P/L. The significant relationship between sedimentation tests and kernel elastic work seems to indicate that elastic work is related to genotype (protein composition). The general tendency was that higher values in kernel elastic work and size corresponded to better dough rheological quality. Mechanical properties of the kernel were significantly related to the elastic behavior measured in a single wheat kernel. The use of the compression test on individual kernels is easy, rapid and nondestructive and therefore seems to show potential use as a rapid tool in breeding to improve wheat quality.

The synthesis of aroma compounds that are utilized as precursors of multiple synthesis chains in the pharmaceutical industries and as ingredients in food and fragrance industries can be carried out using chemical processes, enzyme biocatalysis and whole cell biotransformation. Whole cell biotransformation has the potential of being more environmentally benign than chemical synthesis and more cost-effective as compared to enzyme catalysis. In a recently published study by the authors, the aroma compound Ethyl(3)hydroxybutyrate was produced by whole cell biotransformation under aerobic and anaerobic conditions. The yield of the anaerobic processes was similar to that of the aerobic processes, but additionally generated CO 2 and ethanol as useful by-products. In this chapter we illustrate how the production process of Ethyl(3)hydroxybutyrate by whole cell biotransformation can be integrated into a novel biorefinery concept, based on the finding that the production of Ethyl(3)hydroxybutyrate under anaerobic conditions is efficient and environmentally friendly. CO 2 may be converted to bio-methane together with H 2 produced from excess regenerative power. A life cycle assessment confirmed that the anaerobic whole cell biotransformation process embedded into a biorefinery concept including bio-methane production has a lower environmental impact as compared to a concept based on the aerobic whole cell biotransformation.