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- 2014 (4) (entfernen)
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- Englisch (4)
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- Bacterial milking (2)
- Batch fermentation (2)
- Continuous culture (2)
- Ectoine excretion (2)
- Hofmeister effect (2)
- Kosmotrope (2)
- Osmophobic effect (2)
- Preferential exclusion (2)
- Protein protection (2)
- Aflatoxin (1)
- Alpha-zearalenol (1)
- CLSM (1)
- Conjugation (1)
- Digoxigenin (1)
- ELISA (1)
- Estradiol (1)
- Estrone (1)
- Fermentation (1)
- Flow cytometry (1)
- Hapten (1)
- Hybridoma (1)
- Immunization (1)
- Leaky mutant (1)
- Metabolites (1)
- Microbial conversion (1)
- Monoclonal antibodies (1)
- Mycotoxin biotransformation (1)
- Zearalenone (1)
- Zearalenone-sulfate (1)
- “leaky” mutant (1)
Industrial production of the cell protectant ectoine: protection mechanisms, processes, and products
(2014)
Bacteria, Ärchaea and Eukatya can adapt to saline environments by accumulating compatible solutes in order to maintain an osmotic equilibrium. Compatible solutes are of diverse Chemical structure (sugars, polyols, amino acid derivatives) and are beneficial for bacterial cells not only as osmoregulatory solutes, but also as protectants of proteins by mitigating detrimental effects of ffeezing, drying and high temperatures. The aspartate derivative ectoine is a wide spread compatible solute in Bacteria and possesses additional protective properties compared with other compatible solutes, and stabilizes even vvhole cells against stresses such as UV radiation or cytotoxins. The protective properties of ectoine for proteins can be explained by its strong (kosmotropic) interaction with water and subsequent exclusion ffom Protein surface, the decrease of the solubility of the peptide backbone and the strengthening of intramolecular hydrogen bonds (secondary structures). The stabilizing and UV-protective properties of ectoine attracted industry, which saw the potential to market ectoine as a novel active component in health care products and cosmetics. In joint efforts of industry and research large-scale fermentation procedures have been developed with the halophilic bacterium Halomonas elongata used as a producer strain. The two key technologies that allow for the annual production of ectoine on a scale of tons are the bacterial milking procedure and the development and application of ectoine-excreting mutants (“leaky” mutant). The details of these two procedures including the strain development and fermentation processes will be introduced and current and future applications of ectoine will be discussed.
Biotransformation of the mycotoxin zearalenone by fungi of the genera Rhizopus and Aspergillus
(2014)
Zearalenone (ZEN) is a nonsteroidal estrogenic mycotoxin biosynthesized by various Fusarium fungi. These fungal species frequently infest grains; therefore, ZEN represents a common contaminant in cereal products. The biotransformation of ZEN differs significantly from species to species, and several metabolites are known to be formed by animals, plants, and microorganisms. The aim of the present study was to investigate the microbial conversion of ZEN by species of the genera Rhizopus and Aspergillus representing relevant fungi for food processing (e.g. fermentation). To monitor the ZEN metabolism, ZEN was added to liquid cultures of the different fungal species. After a period of 3 days, the media were analyzed by HPLC-MS/MS for metabolite formation. Two Aspergillus oryzae strains and all seven Rhizopus species were able to convert ZEN into various metabolites, including ZEN-14-sulfate as well as ZEN-O-14- and ZEN-O-16-glucoside. Microbial transformation of ZEN into the significantly more estrogenic α-zearalenol (α-ZEL) was also observed. Additionally, a novel fungal metabolite, α-ZEL-sulfate, was detected. Semi-quantification of the main metabolites indicates that more than 50% of initial ZEN may be modified. The results show that fungal strains have the potential to convert ZEN into various metabolites leading to a masking of the toxin, for example in fermented food.
Industrial production of the cell protectant ectoine: protection mechanisms, processes, and products
(2014)
Bacteria, Archaea and Eukarya can adapt to Saline environments by accumulating compatible solutes in order to maintain an osmotic equilibrium. Compatible solutes are of diverse chemical structure (sugars, polyols, amino acid derivatives) and are beneficial for bacterial cells not only as osmoregulatory solutes, but also as protectants of proteins by mitigating detrimental effects of freezing, drying and high temperatures. The aspartate derivative ectoine is a wide spread compatible solute in Bacteria and possesses additional protective properties compared with other compatible solutes, and stabilizes even whole cells against stresses such as UV radiation or cytotoxins. The protective properties of ectoine for proteins can be explained by its strong (kosmotropic) interaction with water and subsequent exclusion from Protein surface, the decrease of the solubility of the peptide backbone and the strengthening of intramolecular hydrogen bonds (secondary structures). The stabilizing and UV-protective properties of ectoine attracted industry, which saw the potential to market ectoine as a novel active component in health care products and cosmetics. In joint efforts of industry and research large-scale fermentation procedures have been developed with the halophilic bacterium Halomonas elongata used as a producer strain. The two key technologies that allow for the annual production of ectoine on a scale of tons are the bacterial milking procedure and the development and application of ectoine-excreting mutants (“leaky” mutant). The details of these two procedures including the strain development and Fermentation processes will be introduced and current and future applications of ectoine will be discussed.
A novel method that optimizes the screening for antibody-secreting hapten-specific hybridoma cells by using flow cytometry is described. Cell clones specific for five different haptens were analyzed. We selectively double stained and analyzed fixed hybridoma cells with fluorophore-labeled haptens to demonstrate the target-selectivity, and with a fluorophore-labeled anti-mouse IgG antibody to characterize the level of surface expression of membrane-bound IgGs. ELISA measurements with the supernatants of the individual hybridoma clones revealed that antibodies from those cells, which showed the highest fluorescence intensities in the flow cytometric analysis, also displayed the highest affinities for the target antigens. The fluorescence intensity of antibody-producing cells corresponded well with the produced antibodies' affinities toward their respective antigens. Immunohistochemical staining verified the successful double labeling of the cells. Our method makes it possible to perform a high-throughput screening for hybridoma cells, which have both an adequate IgG production rate and a high target affinity.