The aim of this work was to estimate the antibacterial activity of selected essential oils on Pseudomonas orientalis strains isolated from foods. An attempt was also made to identify the mechanisms of the action of the plant oils. Classical methods of assessment of the effectiveness of antimicrobial activity of oils were linked with flow cytometry. It was observed that bergamot, lemongrass, bitter orange, juniper, and black pepper oils have bacteriostatic effect against P. orientalis P49. P. orientalis P110 is sensitive to lime, lemongrass, juniper, rosemary, and black pepper oils. Additionally, plant oils with biostatic effect on P. orientalis limited the intracellular metabolic activity of cells; this was closely linked with the ability of plant oils’ bioactive components to interact with bacteria cell membrane, causing the release of membrane proteins. As a result, the selective permeability of the cell membranes were damaged and the bacterial shape was transformed to coccoid in form.

Application of gas chromatography–olfactometry (GC–O) analysis to pumpernickel bread and its intermediate products obtained during the fermentative process allowed for the recognition of 32 key aroma compounds with specific odor notes. Subsequent quantitation using the stable isotope dilution assay (SIDA) and calculation of odor activity values (OAVs) revealed 22 compounds with OAV > 1, with the highest OAV for 3-methylbutanal with a malty odor (6660), 2-methylbutanal with a malty odor (4560), 3-(methylthio)­propanal with a boiled potato odor (2047), 3-hydroxy-4,5-dimethyl-2­(5H)-furanone with a lovage-like odor (1233), dimethyl trisulfide with a cabbage-like odor (475), 2-phenylethanol with a rosy odor (414), β-damascenone with a boiled apple odor (200), 4-hydroxy-3-methoxybenzaldehyde with a vanilla-like odor (184), 4-hydroxy-2,5-dimethyl-3­(2H)-furanone with a caramel odor (172), and phenylacetladehyde with a honey odor (100). The results showed that aroma of pumpernickel bread is mostly formed during baking; however, the fermentation process influences the formation of several compounds, such as ethyl acetate, 2,3-butanedione, acetic acid, 3-methyl-1-butanol, ethyl butyrate, ethyl lactate, ethyl-3-methyl butyrate, ethyl hexanoate, phenylacetaldehyde, and 2-phenylethanol. Furthermore, the addition of functional components, such as malt and wheat fiber, affects the concentration of several key odorants in the final product, such as 2- and 3-methylbutanals, 3-hydroxy-2-methyl-4H-pyran-4-one, and 4-hydroxy-3-methoxybenzaldehyde.

Fermented products with a pleasant aroma and with strong honey, rose, and fruit odor notes were developed through the biotransformation of a medium containing sour or sweet whey with the addition of L-phenylalanine by the Galactomyces geotrichum mold. In order to obtain the strong honey-rose aroma, G. geotrichum strains were screened and fermentation conditions were optimized to achieve a preferable ratio (>1) of phenylacetaldehyde to 2-phenylethanol by the Ehrlich pathway. This allowed post-fermentation products with the ratio of concentrations of phenylacetaldehyde to 2-phenylethanol being 1.7:1. Additionally, the use of gas chromatography−olfactometry (GC−O) analysis and the calculation of odor activity values (OAVs) allowed 10 key odorants to be identified in post-fermentation products. The highest OAVs were found for phenylacetaldehyde with a honey odor in both sour and sweet whey cultures (3010 and 1776, respectively). In the variant with sour whey, the following compounds with the highest OAVs were 3-methyl-1-butanol (131), 3-(methylthio)-propanal (119), 3-methylbutanal (90), dimethyl trisulfide (71), 2,3butanedione (37), and 2-phenylethanol (29). In the post-fermentation product with sweet whey, the following compounds with the highest OAVs were 3-(methylthio)-propanal (112), dimethyl trisulfide (69), and 2,3-butanedione (41).

Presently, the overuse of antibiotics is a great problem all over the world. The reason for this phenomenon is both primary and secondary resistance. Primary resistance is a congenital feature of microbes and does not depend on its contact with a drug. It is chromosomally coded and cannot be transmitted to other species of bacteria. Secondary resistance, on the other hand, develops as a result of contact with the antibiotic substance. Genes located in plasmids are responsible for the formation of this type of resistance. One plasmid often contains resistance genes for several different antibiotics. Plasmids can transfer gene-encoded resistance from one bacterial cell to another by conjugation and transduction. As a result of the overuse of antibiotics in humans and animals, a growing number of infections -such as pneumonia, salmonellosis, tuberculosis, and gonorrhea -are becoming more troublesome to treat. Antibiotic resistance leads also to longer hospital stays, higher medical costs and finally increased mortality. Now people are finally becoming aware of the consequences of the overuse of antibiotics. Thus, interest in natural bacteriostatic materials, such as plant essential oils, has observably grown. A number of scientific studies have confirmed the antimicrobial activity of plant-derived essential oils against pathogenic bacteria, including Pseudo monas aeruginosa. A very important advantage of plant oils is the fact that they are active in low, sub-lethal concentrations, without provoking the acquisition resistance mechanisms in bacteria. The aim of this review was to explain the mechanisms of antibiotic resistance formation on the example of Pseudomonas aeruginosa and to demonstrate that it is worth looking for alternative treatment methods which can lead to limiting the use of antibiotics. Finally, this work tries to explain how the oils work. 1.Introduction. 2. The characteristics of Pseudomonas genus. 2.1. Pseudomonas aeruginosa. 3. The mechanisms of antibiotic resistance in Pseudomonas spp. 3.1. Intrinsic resistance. 3.2. Adaptive resistance. 3.3. Plasmid resistance. 4. The most common resistances of clinical P. aeruginosa strains to antibiotics. 4.1. Resistance to aminoglycosides. 4.2. Resistance to fluoroquinolones. 4.3. Resistance to cephalosporins. 5. Essential oils from plants as a natural alternative for antibiotics. 5.1. Antibacterial activity of plant EOs against Pseudomonas spp. 5.2. How EOs work on the bacteria cell. 6. Summary PRZECIWDROBNOUSTROJOWA AKTYWNOŚĆ OLEJKÓW ETERYCZNYCH SZANSĄ ROZWIĄZANIA PROBLEMU ANTYBIOTYKOODPORNOŚCI NA PRZYKŁADZIE BAKTERII PSEUDOMONAS SPP.Streszczenie: Nadużywanie antybiotyków stanowi ogromny problem na całym świecie, powodując wzrost antybiotykoodporności u patogennych bakterii. Powodem tego zjawiska jest zarówno oporność pierwotna, jak i wtórna. Oporność pierwotna jest cechą wrodzoną drobnoustrojów i nie zależy od jego kontaktu z lekiem. Kodowana jest chromosomalnie i nie może być przekazywana innym gatunkom bakterii. Oporność wtórna natomiast pojawia się w w...

Currently, there is a growing demand for flavorings, especially of natural origin. It is worth paying attention to the biotechnological processes of flavor production, characterized by simplicity, high efficiency and relatively low cost. In this study, we analyzed the ability of the Galac tomyces geotrichum mold to transform by-products of the dairy industry: sour whey and buttermilk to complex flavour mixtures with pleasant, honey-rose aroma. Furthermore, the aroma complexity of the fermentation product has been carefully identified applying a sensomic approach involving the use of gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and stable isotope dilution assay (SIDA) to identify and quantify aroma compounds. Based on the calculation of odor activity value (OAV), 13 key aroma compounds were present in both tested variants. The highest OAVs were found for phenylacetaldehyde (honey-like) in the buttermilk variant (912) and 2-phenylethanol (rose-like) in the sour whey variant (524). High values of this indicator were also recorded for phenylacetaldehyde (319) and 3-methyl-1-butanol with a fruity aroma (149) in the sour whey culture. The other compounds identified are 3-methylbutanal (malty), 2,3-butanedione (cheesy), isovaleric acid (cheesy), 3-(methylthio)-propanal (boiled potato), butanoic acid (vinegar), (E)-2-nonenal (fatty), ethyl furaneol (burnt sugar), dimethyl trisulfide (cabbage), and acetic acid (vinegar).

The increase in demand for food flavorings due to the shortening and simplification of food production technology also entails an increase in the demand for new technologies for their production. The biotechnological production of aromas is a solution characterized by a high efficiency, an independence from environmental factors and a relatively low cost. In this study, the influence of the implementation of lactic acid bacteria pre-fermentation into the production of aroma compounds by Galactomyces geotrichum on a sour whey medium on the intensity of the obtained aroma composition was analyzed. The monitoring of the culture in terms of biomass buildup, the concentration of selected compounds, and the pH resulted in the confirmation of interactions between the analyzed microorganisms. The post-fermentation product underwent a comprehensive sensomic analysis for the identification and quantification of the aroma-active compounds. The use of gas chromatography−olfactometry (GC−O) analysis and the calculation of odor activity values (OAVs) allowed 12 key odorants to be identified in the post-fermentation product. The highest OAV was found for phenylacetaldehyde with a honey odor (1815). The following compounds with the highest OAVs were 2,3-butanedione with a buttery aroma (233), phenylacetic acid with a honey aroma (197), 2,3-butanediol with a buttery aroma (103), 2-phenylethanol with a rosy aroma (39), ethyl octanoate with a fruity aroma (15), and ethyl hexanoate with a fruity aroma (14).

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