Presence Of Hopping Research Articles

The Probiotic Paradox: Thriving in High-Hopped Sour Beer

The global craft beer market is witnessing substantial growth, with a particular spotlight on sour beers. These unique brews are created through lactic fermentation initiated by lactic acid bacteria (LAB). However, the presence of hops (Humulus lupulus L.), renowned for their antimicrobial properties, can pose a limitation within the realm of sour beer production. This research aims to explore and assess the potential of sour beer as a probiotic beverage. It involves a comparative analysis of the viability of Lacticaseibacillus paracasei subsp. paracasei F19 (F19) and 431 (L431) in a sour beer with an International Bitterness Unit (IBU) value of 22, alongside examining the expression of genes such as horA, horB, horC, hitA, bsrA, and recA, which are associated with hop resistance. The study encompasses the development of two formulations of sour beers characterized by both high hop content and a robust probiotic count (8.44–8.77 log CFU/mL). The findings suggest that both probiotic strains of F19 and L431, are well-suited to produce sour beers with elevated hop levels, demonstrating excellent stability. Notably, the expression of genes responsible for hop resistance exhibited distinct modulation patterns among the two strains. It appears that a higher concentration of bsrA, as observed in strain L431, may be more effective in mitigating the effects of hop-related stress, potentially surpassing the combined expression of horA and bsrA. Nonetheless, further research is essential to validate this observation in gene expression. F19 and L431 emerge as promising candidates for the development of sour beers with increased hop intensity.

BEER AS A SOURCE OF HOP PRENYLATED FLAVONOIDS, COMPOUNDS WITH ANTIOXIDANT, CHEMOPROTECTIVE AND PHYTOESTROGEN ACTIVITY

Beer is an alcoholic beverage consumed worldwide, which is given its typical taste by the presence of hops. Hops contain an array technologically important substances, which are primarily represented by hop resins (humulones, lupulones, humulinones, hulupones, etc.), essential oils (humulene, myrcene, etc.) and tannins (phenolic compounds quercetin, catechin, etc.). In addition to their sensory properties, these molecules contribute to the biological and colloidal stability of beer with their antiseptic and antioxidant properties. Recently, an increased attention has been given to prenylated hop flavonoids, particularly xanthohumol, isoxanthohumol and 8-prenylnaringenin. Xanthohumol is a prenylated chalcone that exhibit antioxidant, anticancer and chemoprotective effects. Its only source in human nutrition is beer, nevertheless a large part of xanthohumol from hops is isomerized by heat to isoxanthohumol and desmethylxanthohumol, from which a racemic mixture of 6- and 8-prenylnaringenins is formed during the beer production. Xanthohumol is also converted to isoxanthohumol by digestion, leading to the formation of 8-prenylnaringenin that is being catalyzed by the enzymes of the intestinal microorganisms as well as liver enzymes. This substance is currently considered to be the most effective natural phytoestrogen.

A lattice model on the rate of in vivo site-specific DNA-protein interactions

We develop a lattice model of site-specific DNA-protein interactions under in vivo conditions where DNA is modelled as a self-avoiding random walk that is embedded in a cubic lattice box resembling the living cell. The protein molecule searches for its cognate site on DNA via a combination of three dimensional (3D) and one dimensional (1D) random walks. Hopping and intersegmental transfers occur depending on the conformational state of DNA. Results show that the search acceleration ratio (= search time in pure 3D route/search time in 3D and 1D routes) asymptotically increases towards a limiting value as the dilution factor of DNA (= volume of the cell/the volume of DNA) tends towards infinity. When the dilution ratio is low, then hopping and intersegmental transfers significantly enhance the search efficiency over pure sliding. At high dilution ratio, hopping does not enhance the search efficiency much since under such situation DNA will be in a relaxed conformation that favors only sliding. In the absence of hopping and intersegmental transfers, there exists an optimum sliding time at which the search acceleration ratio attains a maximum in line with the current theoretical results. However, existence of such optimum sliding length disappears in the presence of hopping. When the DNA is confined in a small volume inside the cell resembling a natural cell system, then there exists an optimum dilution and compression ratios (= total cell volume/volume in which DNA is confined) at which the search acceleration factor attains a maximum especially in the presence of hopping and intersegmental transfers. These optimum values are consistent with the values observed in the Escherichia coli cell system. In the absence of confinement of DNA, position of the specific binding site on the genomic DNA significantly influences the search acceleration. However, such position dependent changes in the search acceleration ratio will be nullified in the presence of hopping and intersegmental transfers especially when the DNA is confined in a small volume that is embedded in an outer cell.

Dissolved Carbon Dioxide Selects for Lactic Acid Bacteria Able to Grow in and Spoil Packaged Beer

Lactic acid bacteria (LAB) are frequently found as beer-spoilage organisms (BSOs). Correctly identifying a LAB as a BSO is problematic, given that there are few known genetic markers that distinguish beer-spoiling from non-beer-spoiling LAB. Currently, genes purported to participate in hop-tolerance mechanisms are heavily relied upon to indicate LAB isolates with the potential to spoil beer, even though these genes do not consistently correlate with beer-spoilage. Though the presence of hops certainly is a significant physiological stress for bacteria in beer, we demonstrate here that the presence of CO2 dissolved in beer is a strong selective pressure for true LAB beer-spoilage ability (i.e., the ability to grow in and spoil a finished and packaged beer). We screened 20 LAB for their capability to survive and grow in gassed beer at 22 and at 30°C, and discuss the results in relation to ethanol and hop tolerance. Functional gene comparisons of nine dissolved CO2-tolerant and nontolerant genomesequenced isolates reveal potential metabolic pathways of interest for further study, specifically those that deal with cell dormancy and stress responses. These results further our understanding of LAB BSOs and have implications for how best to analyze these bacteria in laboratory settings and to test for these bacteria in the brewery.

Chromium Effects on the Structural and Electrical Properties in La0.7Ba0.2Ca0.1Mn1−x Cr x O3

In this paper, we study the structural and electrical properties of the perovskite manganite La0.7Ba0.2 Ca0.1Mn1−xCrxO3, synthesized by the solid-state reaction method. The Rietveld refinement of X-ray diffraction data indicates that there is no structural change owing to Cr substitution in La0.7Ba0.2Ca0.1Mn1−xCrxO3 (0 ≤ x ≤ 0.15). The conductivity of all samples was measured as a function of frequency in the range between 40 and 106 Hz and a temperature ranging from 160 to 300 K. The ac conductance spectrum is found to obey the Jonscher universal power law: Gac = Gdc + Aωn. The variation of the conductivity exponent (n) with temperature confirms the presence of hopping in the conduction process. According to dc conductance study, electronic conduction is found to be dominated by thermally activated hopping. The Cr content affects the activation energy (Ea). Its values decrease from Ea = 72 meV for x = 0 to Ea = 34 meV for x = 0.15.

In situ examination of Lactobacillus brevis after exposure to an oxidizing disinfectant.

Beer is a hostile environment for most microorganisms, but some lactic acid bacteria can grow in this environment. This is primarily because these organisms have developed the ability to grow in the presence of hops. It has been speculated that hop resistance is inversely correlated to resistance against oxidation, and this would have great impact on the use of various disinfectants in the brewing industry. In this study, we cultivated bacteria under aerobic and anaerobic conditions, and then investigated the in situ outgrowth of individual cells into microcolonies on de Man Rogosa Sharpe (MRS) agar after exposure to the oxidizing agent peracetic acid (PAA). An automated microscope stage allowed us to analyse a much larger number of cells over extended periods of incubation. After PAA treatment, the lag time increased markedly, and extensive variation in morphology, μmax as well as stress resistance was observed between and within the tested Lactobacillus brevis strains. The results suggest that aerobic cultivation increased the oxidative stress tolerance in Lactobacillus brevis. The results also show that dead cells are randomly distributed in a microcolony and the majority of non-growing individual cells do not stain with a membrane impermanent dye (Propidium iodide), which indicates that PAA may not destroy the plasma membrane. In conclusion, the developed microscopic analysis of individual cells on MRS agar can provides faster results and more details of cell physiology compared to the traditional CFU method.

Phosphorylation of the effector complex HOPS by the vacuolar kinase Yck3p confers Rab nucleotide specificity for vacuole docking and fusion

The homotypic fusion of yeast vacuoles requires the Rab-family GTPase Ypt7p and its effector complex, homotypic fusion and vacuole protein sorting complex (HOPS). Although the vacuolar kinase Yck3p is required for the sensitivity of vacuole fusion to proteins that regulate the Rab GTPase cycle-Gdi1p (GDP-dissociation inhibitor [GDI]) or Gyp1p/Gyp7p (GTPase-activating protein)-this kinase phosphorylates HOPS rather than Ypt7p. We addressed this puzzle in reconstituted proteoliposome fusion reactions with all-purified components. In the presence of HOPS and Sec17p/Sec18p, there is comparable fusion of 4-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteoliposomes when they have Ypt7p bearing either GDP or GTP, a striking exception to the rule that only GTP-bound forms of Ras-superfamily GTPases have active conformations. However, the phosphorylation of HOPS by recombinant Yck3p confers a strict requirement for GTP-bound Ypt7p for binding phosphorylated HOPS, for optimal membrane tethering, and for proteoliposome fusion. Added GTPase-activating protein promotes GTP hydrolysis by Ypt7p, and added GDI captures Ypt7p in its GDP-bound state during nucleotide cycling. In either case, the net conversion of Ypt7:GTP to Ypt7:GDP has no effect on HOPS binding or activity but blocks fusion mediated by phosphorylated HOPS. Thus guanine nucleotide specificity of the vacuolar fusion Rab Ypt7p is conferred through downstream posttranslational modification of its effector complex.

Phosphoinositides Function Asymmetrically for Membrane Fusion, Promoting Tethering and 3Q-SNARE Subcomplex Assembly

Phosphatidylinositol 3-phosphate (PI(3)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) are essential for rapid SNARE-dependent fusion of yeast vacuoles and other organelles. These phosphoinositides also regulate the fusion of reconstituted proteoliposomes. The reconstituted reaction allows separate analysis of phosphoinositide-responsive subreactions: fusion with SNAREs alone, with the addition of the HOPS tethering factor, and with the further addition of the SNARE complex disassembly chaperones Sec17p and Sec18p. Using assays of membrane tethering, trans-SNARE pairing, and lipid mixing, we found that PI(3)P and PI(4,5)P(2) have distinct functions that are asymmetric with respect to R-SNARE (Nyv1p) and the 3Q-SNAREs (Vam3p, Vti1p, and Vam7p). Fusion reactions with the Q-SNAREs and R-SNARE on separate membranes showed that PI(3)P has two distinct functions. PI(3)P on Q-SNARE proteoliposomes promoted Vam7p binding and association with the other two Q-SNAREs. PI(3)P on R-SNARE proteoliposomes was recognized by the PX domain of Vam7p on Q-SNARE proteoliposomes to promote tethering, although this function could be supplanted by the tethering activity of HOPS. PI(4,5)P(2) stimulated fusion when it was on R-SNARE proteoliposomes, apposed to Q-SNARE proteoliposomes bearing PI(3)P. These functions are essential for the phosphoinositide-dependent synergy between HOPS and Sec17p/Sec18p in promoting rapid fusion.

Effects of hops (Humulus lupulus L.) extract on volatile fatty acid production by rumen bacteria

To determine the effects of hops extract on in vitro volatile fatty acid (VFA) production by bovine rumen micro-organisms. When mixed rumen microbes were suspended in media containing carbohydrates, the initial rates of VFA production were suppressed by β-acid-rich hops extract. The rates of VFA production increased over extended incubations (24 h), and hops extract caused an increase in the propionate to acetate ratio. Hops extract inhibited the growth and metabolism of Streptococcus bovis, but Selenomonas ruminantium and Megasphaera elsdenii were not affected. Likewise, the propionate production of M. elsdenii/S. bovis co-cultures, but not M. elsdenii/S. ruminantium co-cultures, was decreased in the presence of hops extract. These results are consistent with the hypothesis that the hops inhibit Gram-positive lactic acid bacteria (S. bovis), and the rumen microbial community requires a period of adaptation before normal VFA production resumes. Selenomonas bovis and S. ruminantium both produce lactate, which is the substrate for propionate production by M. elsdenii. However, S. ruminantium has an outer membrane, while S. bovis does not. The enhanced production of the gluconeogenesis precursor, propionic acid, provides further evidence that plant secondary metabolites from hops could be used to improve rumen fermentation.

HOPS is an essential constituent of centrosome assembly

Centrosomes direct microtubule organization during cell division. Aberrant number of centrosomes results from alteration of its components and leads to abnormal mitoses and chromosome instability. HOPS is a newly discovered protein isolated during liver regeneration, implicated in cell proliferation. Here, we provide evidence that HOPS is an integral constituent of centrosomes. HOPS is associated with classical markers of centrosomes and found in cytosolic complexes containing CRM-1, γ-tubulin, eEF-1A and HSP70. These features suggest that HOPS is involved in centrosome assembly and maintenance. HOPS depletion generates supernumerary centrosomes, multinucleated cells and multipolar spindle formation leading to activation of p53 checkpoint and cell cycle arrest. The presence of HOPS in cytosolic complexes supports that centrosome proteins might be preassembled in the cytoplasm to then be rapidly recruited for centrosome duplication. Altogether these data show HOPS implication in the control of cell division. HOPS contribution appears relevant to understand genomic instability and centrosome amplification in cancer.

Disorder Effects upon the Two-Magnon Raman Scattering Spectrum in a Hubbard Antiferromagnet

Two-magnon Raman scattering intensity is obtained for a two-dimensional (2D) spin-1/2 antiferromagnet in presence of hopping (off-diagonal) and on-site (diagonal) disorder. For hopping disorder it is seen that a minute amount of disorder leads to a substantial broadening of the Raman lineshape. Whereas the amount of on-site disorder needs to be sufficiently high to obtain any observable broadening in the Raman spectrum. In particular, it is shown that the broadening of the Raman lineshape for the hopping disorder case which arises from an asymmetric energy renormalisation in the magnon spectrum leads to a surprisingly good agreement with the experimentally obtained two-magnon Raman profile for the copper-oxide insulators such as La 2 CuO 4 .