Membrane leakage in Bacillus subtilis 168 induced by the hop constituents lupulone, humulone, isohumulone and humulinic acid

Teuber, Michael; Schmalreck, A.

doi:10.1007/bf00416690

Cited by 99 publications

(97 citation statements)

References 30 publications

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“…The mechanism of the lipophilic region of the cell membrane represents the target site for the antibacterial action of hops bitter resins. Consequently, the antibiotic properties were shown to depend mainly on the hydrophobic parts of the molecules and increased with decreasing solubility [11,12]. This hypothesis was confirmed in B. subtilis, in which lupulone, humulone, and isohumulone caused cell wall lesions by incorporating into the cytoplasmic membrane.…”

Section: Introductionmentioning

confidence: 79%

Supercritical carbon dioxide hops extracts with antimicrobial properties

et al. 2015

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Extracts obtained from hops (Humulus lupulus L., Cannabaceae) by supercritical fluid extraction (SFE), SFE followed by isomerization, as well as by conventional technique, were investigated for their chemical composition and antibacterial activity against selected foodborne pathogens and microorganisms capable to cause the food spoilage. The antibacterial activity of the extracts was compared with the antibacterial activity of xanthohumol, compound known for its broad pharmacological properties, isolated from the raw material remained after the SFE. Xanthohumol (XH, 96%) proved to posses the most prominent activity against all the tested strains, with the MIC values ranged between 2.5 and 20 μg mL -1 . Supercritical hops extract and potassium isomerized supercritical hops extract showed strong antibacterial activity against the tested strains as well. Escherichia coli was not affected by the extracts, meaning that their oral admission would not cause the same problem as antibiotic application in intestinal flora. The chemical composition of the investigated hops extracts was analysed by GC-MS. Contents of α-acids, β-acids, iso-α-acids and xanthohumol in the samples were determined by HPLC.

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Section: Introductionmentioning

confidence: 79%

Supercritical carbon dioxide hops extracts with antimicrobial properties

et al. 2015

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“…Various saponins, tannins, essential oils, organosulfur compounds, and flavonoids have all been shown to have efficacy in this regard [12] [13]. Hops (Humulus lupulus) α-and β-acids are another suite of plant secondary metabolites shown to have antimicrobial properties against Gram-positive bacteria, including rumen bacteria [14] [15]. Up to 25% of the dry weight of hops consists of these acids [16].…”

Section: Introductionmentioning

confidence: 99%

Effects of Spent Craft Brewers’ Yeast on Fermentation and Methane Production by Rumen Microorganisms

Pszczolkowski¹,

Bryant²,

Harlow³

et al. 2016

AiM

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Saccharomyces cerevisiae is a key component of beer brewing and a major by-product. The leftover, spent brewers' yeast from large breweries has been used as a protein supplement in cattle; however the possible advantages of spent yeast from smaller craft breweries, containing much higher levels of bioactive hop acids, have not been evaluated. Hops secondary metabolites from the hops (Humulus lupulus L.) used to make beer are concentrated in the yeast during brewing, and have antimicrobial activity against Gram-positive bacteria. Uncultivated suspensions of bovine rumen microorganisms produced less methane during fructose fermentation when exposed to inactivated, and freeze-dried spent craft brewers' yeast than a bakers' yeast control. The experiment was repeated with caprine rumen microorganisms and ground grass hay as the substrate. Likewise, in the presence of craft brewers' yeast less methane was produced (2.7% vs. 6.9% CH4). Both experiments also revealed a decrease in acetic acid production, but not propionic acid production, when craft brewers' yeast was included. These results indicated that spent yeast could represent a co-product for craft breweries, and a feed supplement for ruminants that has a favorable impact on methane production.

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“…These antibiotic and bacteriostatic properties of hops comprise several inhibitory mechanisms. The described effects of hop compounds on bacteria are permeability changes in the bacterial cell wall (30), leakage of the cytoplasmic membrane and a subsequent inhibition of respiration, and protein, DNA, and RNA synthesis (42), as well as changes in leucine uptake and proton ionophore activity (33). In a recent study (5), we characterized the latter ionophore properties of hop compounds in a cell-free model system via bilayer lipid membrane (BLM) techniques in connection with growth challenges of hop-sensitive and -resistant Lactobacillus brevis strains.…”

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confidence: 99%

Mechanisms of Hop Inhibition Include the Transmembrane Redox Reaction

Behr

Vogel

2010

Appl Environ Microbiol

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In this work, a novel mechanistic model of hop inhibition beyond the proton ionophore action toward (beer spoiling) bacteria was developed. Investigations were performed with model systems using cyclic voltammetry for the determination of redox processes/conditions in connection with growth challenges with hop-sensitive and -resistant Lactobacillus brevis strains in the presence of oxidants. Cyclic voltammetry identified a transmembrane redox reaction of hop compounds at low pH (common in beer) and in the presence of manganese (present in millimolar levels in lactic acid bacteria). The antibacterial action of hop compounds could be extended from the described proton ionophore activity, lowering the intracellular pH, to pronounced redox reactivity, causing cellular oxidative damage. Accordingly, a correlation between the resistance of L. brevis strains to a sole oxidant to their resistance to hop could not be expected and was not detected. However, in connection with our recent study concerning hop ionophore properties and the resistance of hop-sensitive and -tolerant L. brevis strains toward proton ionophores (J. Behr and R. F. Vogel, J. Agric. Food Chem. 57:6074-6081, 2009), we suggest that both ionophore and oxidant resistance are required for survival under hop stress conditions and confirmed this correlation according to the novel mechanistic model. In consequence, the expression of several published hop resistance mechanisms involved in manganese binding/transport and intracellular redox balance, as well as that of proteins involved in oxidative stress under "highly reducing" conditions (cf. anaerobic cultivation and "antioxidative" hop compounds in the growth medium), is now comprehensible. Accordingly, hop resistance as a multifactorial dynamic property at least implies distinct resistance levels against two different mechanisms of hop inhibition, namely, proton ionophore-induced and oxidative stress-induced mechanisms. Beyond this specific model of hop inhibition, these investigations provide general insight on the role of electrophysiology and ion homeostasis in bacterial stress responses to membrane-active drugs.The inflorescences of the hop plant Humulus lupulus are traditionally used for beer brewing, due to the pleasant bitterness of hop compounds in beer and their additional inhibitory effect on bacteria. These antibiotic and bacteriostatic properties of hops comprise several inhibitory mechanisms. The described effects of hop compounds on bacteria are permeability changes in the bacterial cell wall (30), leakage of the cytoplasmic membrane and a subsequent inhibition of respiration, and protein, DNA, and RNA synthesis (42), as well as changes in leucine uptake and proton ionophore activity (33). In a recent study (5), we characterized the latter ionophore properties of hop compounds in a cell-free model system via bilayer lipid membrane (BLM) techniques in connection with growth challenges of hop-sensitive and -resistant Lactobacillus brevis strains. The antibacterial action of iso-␣-acids as prot...

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Membrane leakage in Bacillus subtilis 168 induced by the hop constituents lupulone, humulone, isohumulone and humulinic acid

Cited by 99 publications

References 30 publications

Supercritical carbon dioxide hops extracts with antimicrobial properties

Supercritical carbon dioxide hops extracts with antimicrobial properties

Effects of Spent Craft Brewers’ Yeast on Fermentation and Methane Production by Rumen Microorganisms

Mechanisms of Hop Inhibition Include the Transmembrane Redox Reaction

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