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K C Schuster

Publications and source records attributed to K C Schuster.

10 recordsLinked to original sources
PubMed2001

Rapid method for the discrimination of red wine cultivars based on mid-infrared spectroscopy of phenolic wine extracts.

Mid-infrared spectroscopy and UV-vis spectroscopy combined with multivariate data analysis have been applied for the discrimination of Austrian red wines, including the cultivars Cabernet Sauvignon, Merlot, Pinot Noir, Blaufränkisch (Lemberger), St. Laurent, and Zweigelt. Both authentic wines and their phenolic extracts were investigated by attenuated total reflectance (ATR)-mid-infrared spectroscopy. Phenolic extracts were also investigated by UV-vis spectroscopy. The wine extracts were obtained by solid-phase extraction with C-18 columns and elution by methanol containing 0.01% hydrochloric acid. Hierarchical cluster analysis was performed with mid-infrared spectra of both wines and extracts, as well as with UV-vis spectra of the phenolic extracts. Data processing involved vector normalization and derivation of the spectra. Due to varying concentrations of main components including sugar and organic acids, satisfactory classification of untreated wines was not achieved. However, when using mid-infrared spectra of the phenolic extracts, almost complete discrimination of all cultivars investigated was achieved. The use of UV-vis spectroscopy for cultivar discrimination was found to be limited to the authentication of the Burgundy species Pinot Noir. In addition, soft independent modeling of class analogy was applied to the mid-infrared spectra of the extracts. It was possible to establish class models for five different wine cultivars and to classify test samples correctly.

Anthocyanins↗
PubMed2001

Degeneration of solventogenic Clostridium strains monitored by Fourier transform infrared spectroscopy of bacterial cells.

Strain degeneration in solventogenic clostridia is a known problem in the technical acetone-butanol fermentation bioprocess, especially in the continuous process mode. Clostridial strain degeneration was studied by Fourier transform infrared (FT-IR) spectroscopy of the bacterial cells. Degenerative variant formation in two strains, Clostridium beijerinckii NCIMB 8052 and Clostridium species AA332, was detected spectroscopically. Colonies on solid media were sampled, or assayed directly in situ by IR microscopy. It has previously been shown that the distinctive acidogenic and solventogenic physiological phases of Clostridium acetobutylicum in liquid medium can be discriminated by FT-IR spectroscopy. This was confirmed here for C. beijerinckii NCIMB 8052. The proportion of degenerate cells in a mixed population in liquid medium could be quantified, as the spectral features change in different ways during the normal growth cycle of wild type organisms and degenerate variants in batch culture. This opens a new perspective for physiology-based process monitoring and control, especially of the continuous acetone-butanol fermentation.

Acetone↗
PubMed2000

Multidimensional information on the chemical composition of single bacterial cells by confocal Raman microspectroscopy.

In many biotechnological processes, living microorganisms are used as biocatalysts. Biochemical engineering science is becoming more aware that individual cells of an organism in a process can be fairly inhomogeneous regarding their properties and physiological status. Raman microspectroscopy is a novel approach to characterize such differentiated populations. Cells of the anaerobic bacterium Clostridium beijerinckii were dried on transparent support surfaces. The laser beam of a confocal Raman microscope was focused on individual cells viewed through the objective. Single bacterial cells in size approximately 1 microm and sample mass approximately 1 pg could be analyzed within a few minutes, when placed on a calcium fluoride support and using excitation at 632.8 nm. Spectral features could be attributed to all major cell components. Cells from a morphologically differentiated culture sample showed different compositions, indicating the presence of subpopulations. As a reference, the storage polymer granulose was detected. The multidimensional information in Raman spectra gives a global view on all major components of the cell at once, complementing other more specific information-rich methods for single-cell analysis. The method can be used, for example, to study heterogeneities in a microbial population.

Clostridium↗
PubMed2000

Monitoring the physiological status in bioprocesses on the cellular level.

The trend in bioprocess monitoring and control is towards strategies which are based on the physiological status of the organism in the bioprocess. This requires that the measured process variables should be biologically meaningful in order to apply them in physiologically based control strategies. The on-line monitoring equipment available today mostly derives information on the physiological status indirectly, from external variables outside the cells. The complementary approach reviewed here is to analyse the microbial cells directly, in order to obtain information on the internal variables inside the cells. This overview covers methods for analysis of whole cells (as a population or as a single cell), for groups of cellular components, and for specific compounds which serve as markers for a certain physiological status. Physico-chemical separation methods (chromatography, electrophoresis) and reactive analysis can be used to analyse elemental and macromolecular composition of cells. Spectroscopic methods (mass, dielectric, nuclear magnetic, infrared, and Raman) have only recently been applied to such complex multicomponent mixtures such as microbial cells. Spectroscopy and chemical separation methods produce large amounts of data, which can often be used in the best way by applying chemometrics. Some of the methods can yield information not just on the average of the microbial cell population, but also on the distribution of sub-populations. The suitability of the methods for on-line coupling to the bioprocess is discussed. Others not suitable for on-line coupling can be established in routine off-line analysis procedures. The information gained by the methods discussed can mainly be used to establish better knowledge of the basis for monitoring and control strategies. Some are also applicable in real-time monitoring and control.

Adenosine Triphosphate↗
PubMed2000

Single-cell analysis of bacteria by Raman microscopy: spectral information on the chemical composition of cells and on the heterogeneity in a culture.

In the acetone-butanol (ABE) fermentation process, the utilised organisms from the group of the solventogenic Clostridia go through a complex cell-cycle. The role of different cell types in product formation is not understood in detail yet. We aim to use Raman spectroscopy to characterise the population distribution in Clostridium cultures. Cell suspensions were dried on calcium fluoride carriers. Raman spectra of single cells were obtained using a confocal Raman microscope (Dilor, Lille, France). The laser beam was focused on individual cells through the microscope objective. Spectra with good signal-to-noise ratio were obtained. Cells of different morphology, but also apparently similar cells, showed different spectra. Several cell components could be detected and varied in quantity. Compared to other methods for single-cell analysis, the new method is much more time-consuming to analyse one individual cell. However, a large amount of chemical information is obtained from each single cell in a non-destructive, non-invasive way. Raman microscopy appears to be a suitable method for studying population distributions in bacterial cultures.

Clostridium↗
PubMed2000

Conversion of solvent evaporation residues from the AB- (acetone - butanol) bioprocess into bacterial cells accumulating thermoplastic polyesters.

In a bioconversion study based on utilisation of by-products from the AB- (acetone - butanol) bioprocess a new isolated gram-negative solvent tolerant bacterium was used to convert the AB process residue after removal of the major part of the solvents. The bacterium identified as a representative of the genus Alcaligenes (designated as Alcaligenes sp. G) was capable of growth up to optical densities ranging from 8 to 20 and simultaneously of polyhydroxyalkanoate-(PHA-)accumulation up to 40% per dry weight. A standardised medium based on AB by-products containing 7 g/l of butyrate and 5 g/l of acetate at pH 7.5 was used in our studies for bioconversion into PHAs. Concentrations of 1-butanol, which is known for its membrane damaging properties in microorganisms, were tolerated in the AB by-products medium up to 4 g/l without significant inhibition of cellular growth. No inhibition of growth was observed, when the medium was adjusted to 40 g/l butyrate. Due to the toxicity of the remaining 1-butanol maintenance of sterility is of no high priority during the process. The use of acetate and butyrate from an AB process is expected to provide a higher return-on-investment than the combustion of biogas to help meet energy demands.

Acetone↗
PubMed2000

The cause of "acid-crash" and "acidogenic fermentations" during the batch acetone-butanol-ethanol (ABE-) fermentation process.

Experiments were performed to determine the cause of "acid crash", a phenomenon which occasionally occurs in pH-uncontrolled batch fermentations resulting in premature cessation of ABE (acetone butanol) production. The results indicate that "acid crash" occurs when the concentration of undissociated acids in the broth exceeds 57 - 60 mmol/l. Prevention can be achieved by introducing some limited pH control to minimize the concentration of undissociated acids or by slowing the metabolic rate, and thus the rate of acid production, by, for example, lowering the fermentation temperature. "Acidogenic fermentations", which occur when batch fermentations are performed at pH values close to neutrality, are due to rapid production of acids followed by inhibition of solventogenesis when the total acid concentration reaches 240 - 250 mmol/l. Solventogenesis can be achieved at these pH values by lowering the glucose uptake rate / acid production rate by use of e.g. elevated glucose or lowered yeast extract concentrations in the growth medium.

Acetone↗
PubMed2000

Conversion of solvent evaporation residues from the AB- (acetone-butanol) bioprocess into bacterial cells accumulating thermoplastic polyesters.

In a bioconversion study based on utilisation of by-products from the AB- (acetone-butanol) bioprocess a new isolated gram-negative solvent tolerant bacterium was used to convert the AB process residue after removal of the major part of the solvents. The bacterium identified as a representative of the genus Alcaligenes (designated as Alcaligenes sp. G) was capable of growth up to optical densities ranging from 8 to 20 and simultaneously of polyhydroxyalkanoate- (PHA-)accumulation up to 40% per dry weight. A standardised medium based on AB by-products containing 7 g/l of butyrate and 5 g/l of acetate at pH 7.5 was used in our studies for bioconversion into PHAs. Concentrations of 1-butanol, which is known for its membrane damaging properties in micro-organisms, were tolerated in the AB by-products medium up to 4 g/l without significant inhibition of cellular growth. No inhibition of growth was observed, when the medium was adjusted to 40 g/l butyrate. Due to the toxicity of the remaining 1-butanol maintenance of sterility is of no high priority during the process. The use of acetate and butyrate from an AB process is expected to provide a higher return-on-investment than the combustion of biogas to help meet energy demands.

1-Butanol↗
PubMed1996

Dynamics in oxygen-induced changes in S-layer protein synthesis from Bacillus stearothermophilus PV72 and the S-layer-deficient variant T5 in continuous culture and studies of the cell wall composition.

Stable synthesis of the hexagonally ordered (p6) S-layer protein from the wild-type strain of Bacillus stearothermophilus PV72 could be achieved in continuous culture on complex medium only under oxygen-limited conditions when glucose was used as the sole carbon source. Depending on the adaptation of the wild-type strain to low oxygen supply, the dynamics in oxygen-induced changes in S-layer protein synthesis was different when the rate of aeration was increased to a level that allowed dissimilation of amino acids. If oxygen supply was increased at the beginning of continuous culture, synthesis of the p6 S-layer protein from the wild-type strain (encoded by the sbsA gene) was immediately stopped and replaced by that of a new type of S-layer protein (encoded by the sbsB gene) which assembled into an oblique (p2) lattice. In cells adapted to a prolonged low oxygen supply, first, low-level p2 S-layer protein synthesis and second, synchronous synthesis of comparable amounts of both types of S-layer proteins could be induced by stepwise increasing the rate of aeration. The time course of changes in S-layer protein synthesis was followed up by immunogold labelling of whole cells. Synthesis of the p2 S-layer protein could also be induced in the p6-deficient variant T5. Hybridization data obtained by applying the radiolabelled N-terminal and C-terminal sbsA fragments and the N-terminal sbsB fragment to the genomic DNA of all the three organisms indicated that changes in S-layer protein synthesis were accompanied by chromosomal rearrangement. Chemical analysis of peptidoglycan-containing sacculi and extraction and recrystallization experiments revealed that at least for the wild-type strain, a cell wall polymer consisting of N-acetylglucosamine and glucose is responsible for binding of the p6 S-layer protein to the rigid cell wall layer.

Adaptation, Physiological↗