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W artykule omówiono metody i techniki rekombinacji genetycznej drożdży in vitro. Przedstawiono korzyści z zastosowania drożdży transgenicznych w browarnictwie.
Corrosion is an electrochemical process consisting of an anodic reaction involving the ionization (oxidation) of the metal (the corrosion reaction), and a cathodic readion based on the reduction of a chemical species, processes at metal surfaces are associated with microorganisms, or the products of their metabolic activities including enzymes, exopolymers, organic and inorganic acids, as well as volatile compounds such as ammonia or hydrogen sulfide. These can affect cathodic and/or anodic reactions, thus altering electrochemistry at the biofilm/metal interface. Various mechanisms of biocorrosion, reflecting the variety of physiological activities carried out by different types of microorganisms, are identified and recent insights into these mechanisms reviewed. Many modern investigations have centered on the microbially-influenced corrosion of ferrous and copper alloys and particular microorganisms of interest have been the sulfate-reducing bacteria (SRB) and metal (especially manganese) - depositing bacteria. The importance of microbial consortia and the role of extracellular polymeric substances in bio- corrosion are emphasized. The contribution to the study of biocorrosion of modern analytical techniques, such as atomic force microscopy, Auger electron, X-ray photoelectron and Mössbauer spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and micro- sensors, is discussed.
The formation of sulphur compounds in beer is a subject of great interest. Such compounds, especially sulphur volatile compounds (VSC), are essential for the aroma of beer (and some of them were identified as key compounds, i.e. dimethyl sulfide & dimethal trisulfide, in which they can play an attractive or a repulsive role (for example: accumulate sulphur atoms from the growth medium). Sulphur compounds essentially arise from common sulphur-bearing precursors such amino acids, i.e. methionine, which being the most commonly found, moreover, methionine repress the cysteine-induced increase in the H2S production but had no effect on the formulation of SO2. Differences are also seen in H2S compared with S02 production in response to nitrogen levels in wort. However, biochemically H2S and S02 production are closely linked, environmental condition in brewery can have different effects on their rate of formation. These facts provide insights into possible opportunities to modulate the levels of H2S and S02 in industrial fermentations. Analyses on worts indicated that thio- esters resulted from fermentation, whereas the polysulfides derive primarily from malt and hop. Changes in process conditions such as temperature, aeration, nutrient type and availability as well as metabolite concentrations can significantly affect brewer's yeast metabolism during fermentation. Alterations in these factors serve to stress, which causes changes in the cellular composition that may either directly or indirectly impact on fermentative performance.
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