Hop Resistance 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.

A hypothesis-based hop microbiology laboratory module testing the plausibility of the mythical origin of the India Pale Ale.

As one of the most famous fermented drinks in the world, beer is an especially relatable topic for microbiology courses. Here, we describe a short and easily adaptable module based on the antibacterial properties of hops used in brewing. By the 15th century, beer recipes included hops (the flower of the Humulus lupulus plant) as a bittering agent and antimicrobial. By the 19th century, the highly hopped Indian Pale Ale (IPA) became popular, and a modern myth has emerged that IPAs were invented to survive long ocean voyages such as from Britain to India. With that myth in mind, we designed a hypothesis-driven microbiology lab module that tests the plausibility of this brewing myth-namely that highly hopped beers possess enough antibacterial activity to prevent spoilage, while lowly hopped beers do not. The overall design of the module is to test the antimicrobial properties of hops using petri plates containing varying concentrations of hop extract. The module includes hypothesis generation and testing related to bacterial physiology and cell envelope morphology (hops are not equally effective against Gram-positive and Gram-negative bacteria) and to mechanisms of antimicrobial resistance (as beer spoilage bacteria have repeatedly evolved hop resistance). Pre- and post-assessment showed that students made significant gains in the learning objectives for the module, which encourages critical thinking and hypothesis testing by linking microbial physiology and antimicrobial resistance to an important and topical real-world application.

The combination of omics strategies to evaluate starter and probiotic strains in the Catharina sour Brazilian-style beer

Catharina sour, the first internationally recognized Brazilian beer, is characterized by fermentation with lactic acid bacteria (LAB), which may have probiotic potential, and the addition of fruit juice. This study aimed to evaluate the use of the starter Streptococcus thermophilus TH‐4 (TH‐4) and the probiotics Lacticaseibacillus paracasei F19 and 431, associated with Saccharomyces cerevisiae US-05, in the absence (control)/presence of passion fruit or peach juices. Evaluation proceeded during fermentation and storage by enumeration using pour-plate and qPCR; gene expressions of hop resistance; proteome by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS); and odor, flavor, and metabolome by Headspace Solid-Phase Microextraction (HS-SPME), coupled with the gas chromatography–mass spectrometry (GC–MS) analysis. We concluded that the strains studied are recommended for applications in sour beers, due to the presence of defense mechanisms like membrane adhesion and H + pump. Furthermore, HS-SPME/GC-MS indicated that the strains may contribute to the beer flavor and odor.

New insights into the role of key microorganisms and wooden barrels during lambic beer fermentation and maturation

Belgian lambic beers are still produced through traditional craftsmanship. They rely on a spontaneous fermentation and maturation process that is entirely carried out in wooden barrels. The latter are used repetitively and may introduce some batch-to-batch variability. The present systematic and multiphasic study dealt with two parallel lambic beer productions carried out in nearly identical wooden barrels making use of the same cooled wort. It encompassed a microbiological and metabolomic approach. Further, a taxonomic classification and metagenome-assembled genome (MAG) investigation was based on shotgun metagenomics. These investigations provided new insights into the role of these wooden barrels and key microorganisms for this process. Indeed, besides their role in traditionality, the wooden barrels likely helped in establishing the stable microbial ecosystem of lambic beer fermentation and maturation by acting as an inoculation source of the necessary microorganisms, thereby minimizing batch-to-batch variations. They further provided a microaerobic environment, which aided in achieving the desirable succession of the different microbial communities for a successful lambic beer production process. Moreover, these conditions prevented excessive growth of acetic acid bacteria and, therefore, uncontrolled production of acetic acid and acetoin, which may lead to flavor deviations in lambic beer. Concerning the role of less studied key microorganisms for lambic beer production, it was shown that the Acetobacter lambici MAG contained several acid tolerance mechanisms toward the harsh environment of maturing lambic beer, whereas genes related to sucrose and maltose/maltooligosaccharide consumption and the glyoxylate shunt were absent. Further, a Pediococcus damnosus MAG possessed a gene encoding ferulic acid decarboxylase, possibly contributing to 4-vinyl compound production, as well as several genes, likely plasmid-based, related to hop resistance and biogenic amine production. Finally, contigs related to Dekkera bruxellensis and Brettanomyces custersianus did not possess genes involved in glycerol production, emphasizing the need for alternative external electron acceptors for redox balancing.

Genomic Analysis and In Vitro Investigation of the Hop Resistance Phenotype of Two Novel Loigolactobacillus backii Strains, Isolated from Spoiled Beer.

Loigolactobacillus backii is an important beer-spoiling species, exhibiting high hop tolerance. Here, we present the annotated whole genome sequence of two recently isolated strains, Lg. backii KKP 3565 and KKP 3566. Firstly, to study the genetic basis of the persistence of the two isolates in beer, a comprehensive bioinformatic analysis ensued. Their chromosome map was constructed, using whole-genome sequencing and assembly, revealing that the two strains carry genomes with a length of 2.79 Mb with a GC content of 40.68%. An average nucleotide identity (ANI) analysis demonstrated that the novel strains possess unique genomic sequences, also confirming their classification into the Lg. backii species. Their genome harbors numerous insertion sequences and plasmids, originating from other beer-spoiling species. Regarding their adaptation in brewery environment, homologous genes that confer resistance to hop were spotted, while the impact of hop bitters and pure beer on bacterial growth was investigated, in vitro. In brief, low hop concentrations were found to induce the proliferation of strains, while a higher concentration negatively affected their growth. Nonetheless, their ability to survive in pure beer indicated their tolerance to high hop concentrations. These results offer insight into the capacity of Lg. backii KKP 3566 and Lg. backii KKP 3566 to tolerate the extreme conditions prevalent in the brewery environment.

Inferring the energy sensitivity and band gap of electronic transport in a network of carbon nanotubes

Since the industrialization of single-phase nanomaterial-based devices is still challenging, intensive research focus has been given to complex materials consisting of multiple nanoscale entities, including networks and matrices of nanowires, nanotubes, nanoribbons, or other large molecules; among these complex materials, networks of carbon nanotubes are a typical example. Detailed knowledge of the energy sensitivity and band gap of electronic transport in such a material system is difficult to detect, despite its importance in electronic, energetic and sensing applications. Here, we propose a new methodology to obtain these quantities using the measured Seebeck coefficient at a certain temperature but different Fermi levels. We discover that the network consisting of semiconducting (11,10)-carbon nanotubes actually exhibits metallic transport at room temperature. It is also interesting to verify that intrananotube ballistic transport is dominant over diffusive scattering by long-range disorder, as well as the quantum hopping resistance at the contact points. The transport asymmetry ratio between the holes and electrons (1.75) is similar to the value observed in pristine graphene samples (1.50).

Draft Genome Sequence of Lactiplantibacillus plantarum NMZ-1139, Isolated from Whisky Mash

ABSTRACTLactiplantibacillus plantarum NMZ-1139 was isolated from whisky mash and applied to sour beer production. Here, we report the draft genome sequence of L. plantarum NMZ-1139, which contains 3,117 protein-coding sequences, including genes associated with hop resistance, such as horA and hitA.

Study of Beer Spoilage Lactobacillus nagelii Harboring Hop Resistance Gene horA

Lactic acid bacteria (LAB) cause the majority of beer spoilage incidents in the brewing industry. Previous studies revealed that the hop resistance genes, horA and horC, are applicable to the species-independent determination of beer spoilage ability of LAB. However, novel beer spoilage LAB species are occasionally emerging, and their insights should be shared in the industry to prevent spoilage incidents by these unknown species. In this study, Lactobacillus nagelii ABBC668 strain, isolated from spoiled pilsner-type beer, was investigated, as L. nagelii has been poorly characterized as a beer spoiler. The beer spoilage ability and hop resistance genes of L. nagelii ABBC668 were examined. Results showed that L. nagelii ABBC668 harbored hop resistance gene horA and exhibited beer spoilage ability. Also, it was considered that horA harbored by ABBC668 was acquired via horizontal gene transfer and had an unstable nature compared to that of Lactobacillus brevis. The unstable nature may account for the less frequent encounter of beer spoilage L. nagelii strains in the brewing industry. Furthermore, ABBC668 showed similar motility to other L. nagelii strains. To our knowledge, this is the first report of L. nagelii as a beer spoilage species.

Effects of Sb Doping and Preferred Crystal Orientation on the Performance of Electro-Plated Cu2o Resistive Random Access Memory

Effects of antimony doping and film preferred crystal orientation on the performance and stability of electro-plated cuprous oxide (Cu2O) resistive random access memory (RRAM) devices were studied. Previous study indicated that electro-plated Cu2O with a small amount of antimony doping improves film uniformity, surface roughness1. The Sb doped film (Cu2O:Sb) also has a smaller grain size as compared to that of an un-doped cuprous oxide (u-Cu2O) film at same PH plating solution. SEM image of the grain boundaries of the Cu2O:Sb film also indicated that the film is more vertically oriented as compare to that of the u-Cu2O film. As some literatures reported, the conductive path (or charge hopping distance) of the RRAM is likely shorter if electrons hopping take place along the vertical-like grain boundaries. It will also reduce the voltage to set the conductive path formation (or set up of the charge hopping path). Moreover, uniform film and smoother surface are likely to have a stable set/reset performance because more uniform charge hopping distance and/or hopping site distribution.Our studies show that the forming voltages of a 700nm electroplated Cu2O:Sb (~2 at. %) and u-Cu2O (strongly (111) oriented) films are about 4V and 7V, respectively. Some of Cu2O:Sb RRAMs are forming free. The set voltages (Vset) of Cu2O:Sb and u-Cu2O RRAMs are ranging from 1.5V to 2.6V and from 1.2V to 9V, respectively. The reset voltages (Vreset) are 1.2V ~ 1.5V and 1V ~ 2V, respectively. The ratio of high/low resistance state (HRS/LRS) for both of the RRAMs is about two orders of magnitude, and no decay is observed for retention test of 5000 seconds at 0.1V. These results indicate that Sb doping does reduce forming (likely forming free) and significantly stabilize its set voltage.Surface morphology and texture of a (200)-preferred Cu2O film is very different from (111)-preferred film2 − 4. For a (200)-preferred film, its grains’ boundaries are more perpendicular to the plating surface (or electrode). This kind of film texture is also likely can help forming shorter conductive paths and/or stabilize the charge hopping resistance. It is similar to our Cu2O:Sb film texture as previous described. For Cu2O:Sb film, the XRD intensity ratio (R) of (111) to (200) phase is ~1. While the u-Cu2O is strongly (111)-preferred film with R= 12. Preferred crystal orientation change will give rise to varying in vacancy, defects, and trap charge distribution along the hopping paths. These variations can affect charge hopping resistance and its characteristics. Charge hopping in film with vertical-like grain boundaries is believed to be a shorter and easier path.Performance of preferred crystal orientation dependence of the u-Cu2O RRAM is investigated. A (200)-preferred u-Cu2O film with R= 0.185 was used. Its RRAM performance improved in forming voltage of ~5V and in HRS/LRS ratio with three orders of magnitude.In short, Cu2O:Sb film can be a good candidate for RRAM application because of its low cost, potential forming free, low set/reset voltages and stability. Sb doping may have helped forming shorter conductive paths due to its vertical like gains boundaries, less charge hopping resistance due to more uniformly distributed Sb induced hopping sites. Improved performance of (200)-preferred u-Cu2O RRAM may result from vacancy, defects and trap charge distribution change along the hopping paths.Reference 1. Baek, S. K., Kwon, Y. H., Shin, J. H., Lee, H. S., & Cho, H. K. “Low‐Temperature Processable High‐Performance Electrochemically Deposited p‐Type Cuprous Oxides Achieved by Incorporating a Small Amount of Antimony” Advanced Functional Materials, 25, (2015) 52142. J. Siegfried and K.S. Choi, “Electrochemical Crystallization of Cuprous Oxide with Systemic Shape Evolution” Advanced Materials, 16 (2004) 17433. E. Rakhshani and J. Varghese “Surface texture in electrodeposited films of cuprous oxide” J. Materials Science 23 (1988) 38474. H. Lee, I.C. Leu, C.L. Liao, K.Z. Fung “The structural evolution and electrochemical properties of the textured Cu2O thin films” J. Alloy Compounds 436 (2007) 241

Genomic analysis of a hop-resistance Lactobacillus brevis strain responsible for food spoilage and capable of entering into the VBNC state

BackgroundLactobacillus brevis is a major contaminant of spoiled beer. And it was able to enter VBNC state and cause false negative detection, which poses a major challenge to the brewing industry. MethodsThe genomic DNA of L. brevis BM-LB13908 was extracted and purified to form a sequencing library that meets the quality requirements and was sequenced. The sequencing results were then screened and assembled to obtain the entire genome sequence of L. brevis. Predicted genes were annotated by GO database, KEGG pathway database and COG functional classification system. ResultsThe final assembly yielded 275 scaffolds of a total length of 2 840 080 bp with a G + C content of 53.35%. There were 2357, 701, 1519 predicted genes with corresponding GO functional, COG functional, and KEGG biological pathway annotations, respectively. The genome of L. brevis BM-LB13908 contains hop resistance gene horA and multiple genes related to the formation of VBNC state. ConclusionsThis report describes the draft genome sequence of L. brevis BM-LB13908, a spoilage strain isolated from finished beer sample. This study may support further study on L. brevis and other beer spoilage bacteria, and prevent and control beer spoilage caused by microorganisms.

A Plasmid-Encoded Putative Glycosyltransferase Is Involved in Hop Tolerance and Beer Spoilage in Lactobacillus brevis.

Lactobacillus brevis beer-spoiling strains harbor plasmids that contain genes such as horA, horC, and hitA which are known to confer hop tolerance. The L. brevis beer-spoiling strain UCCLBBS124, which possesses four plasmids, was treated with novobiocin, resulting in the isolation of UCCLBBS124 derivatives exhibiting hop sensitivity and an inability to grow in beer. One selected derivative was shown to have lost a single plasmid, here designated UCCLBBS124_D, which harbors the UCCLBBS124_pD0015 gene, predicted to encode a glycosyltransferase. Hop tolerance and growth in beer were restored when UCCLBBS124_pD0015 was introduced in one of these hop-sensitive derivatives on a plasmid. We hypothesize that this gene modifies the surface composition of the polysaccharide cell wall, conferring protection against hop compounds. Furthermore, the introduction of this gene in trans in L. brevis UCCLB521, a strain that cannot grow in and spoil beer, was shown to furnish the resulting strain with the ability to grow in beer, while its expression also conferred phage resistance. This study underscores how the acquisition of certain mobile genetic elements plays a role in hop tolerance and beer spoilage for strains of this bacterial species.IMPORTANCELactobacillus brevis is a member of the lactic acid bacteria and is often reported as the causative agent of food or beverage spoilage, in particular, that of beer. Bacterial spoilage of beer may result in product withdrawal or recall, with concomitant economic losses for the brewing industry. A very limited number of genes involved in beer spoilage have been identified and primarily include those involved in hop resistance, such as horA, hitA, and horC However, since none of these genes are universal, it is clear that there are likely (many) other molecular players involved in beer spoilage. Here, we report on the importance of a plasmid-encoded glycosyltransferase associated with beer spoilage by L. brevis that is involved in hop tolerance. The study highlights the complexity of the genetic requirements to facilitate beer spoilage and the role of multiple key players in this process.

Spoilage Lactic Acid Bacteria in the Brewing Industry.

Lactic acid bacteria (LAB) have caused many microbiological incidents in the brewing industry, resulting in severe economic loss. Meanwhile, traditional culturing method for detecting LAB are time-consuming for brewers. The present review introduces LAB as spoilage microbes in daily life, with focus on LAB in the brewing industry, targeting at the spoilage mechanism of LAB in brewing industry including the special metabolisms, the exist of the viable but nonculturable (VBNC) state and the hop resistance. At the same time, this review compares the traditional and novel rapid detection methods for these microorganisms which may provide innovative control and detection strategies for preventing alcoholic beverage spoilage, such as improvement of microbiological quality control using advanced culture media or different isothermal amplification methods.

Beer-spoilage characteristics of Staphylococcus xylosus newly isolated from craft beer and its potential to influence beer quality.

To meet demands for fresh flavor and unique taste from beer consumer, there is an increase in the popularity of craft beer, which is more susceptible to microbial contamination than the industry beer. A beer‐spoilage strain was isolated from craft beer and identified as Staphylococcus xylosus strain BS7. The isolate BS7 showed that high beer‐spoilage ability at low temperature (4°C), low pH (4.0) and high ethanol concentration (7.0%, v/v). Compared with the other known strains of S. xylosus, strain BS7 was resistant to hop compounds and had an evolutionary stability in hop resistance. Strain BS7 was able to grow quickly and utilizes nutrients in commercial beer, produces organic acids and biogenic amines, and changes beer flavor profile. These results suggest that S. xylosus strain BS7 is a beer‐spoilage strain with the danger, which can lead to the beer‐spoilage issues during craft beer production.

Highly Flexible Hydrogen Boride Monolayers as Potassium-Ion Battery Anodes for Wearable Electronics.

The rapid development of wearable electronics has revealed an urgent need for low-cost, highly flexible, and high-capacity power sources. In this sense, emerging rechargeable potassium-ion batteries (KIBs) are promising candidates owing to their abundant resources, low cost, and lower redox potential in nonaqueous electrolytes compared to lithium-ion batteries. However, the fabrication of flexible KIBs remains highly challenging because of the lack of high-performance flexible electrode materials. In this work, we investigated the mechanical properties and electrochemical performance of a recently developed hydrogen boride (BH) monolayer as a high-performance anode material on the basis of density functional theory formalism. We demonstrated that (i) BH presents ultralow out-of-plane bending stiffness, rivaling that of graphene, which endows it with better flexibility to accommodate the repeated bending, rolling, and folding on wearable device operation; (ii) high in-plane stiffness (157 N/m along armchair and 109 N/m along zigzag) of BH makes the electrode stable against pulverization upon external and internal strains. More importantly, a BH electrode delivers a low voltage of ∼0.24 V in addition to desired K-ion affinity and hopping resistance, which remains very stable with the bending curvature. Emerged H vacancies in electrodes were found to improve both the K-ion intercalation and K-ion hopping, yielding a high theoretical capacity (1138 mAh/g), which was among the highest reported values in the literature for K-ion anode materials. All of the presented results suggested that a BH electrode could be used as a brand-new flexible and lightweight KIB anode with high capacity, low voltage, and desired rate performance.

Current Noise and Efficiency Droop of Light-Emitting Diodes in Defect-Assisted Carrier Tunneling from an InGaN/GaN Quantum Well

The current dependences of the spectral noise density and quantum efficiency in green and blue light-emitting diodes with InGaN/GaN quantum wells (QWs) are measured. It is shown that the noise level greatly increases at high currents at which there is a quantum efficiency droop. The mechanism by which the current noise is formed is associated with hopping transport via the deep states of color centers in GaN across the n barrier of an InGaN/GaN QW. The source of the noise is the hopping resistance of the space-charge region, which limits the current of thermally activated electrons into the QW. The efficiency droop and the increase in noise level are attributed to a change in the electric-field direction near the QW at high injection levels and to an increase in the tunneling leakage of holes from the QW. It is shown that the experimental frequency-related noise spectra having the shape of a Lorentzian spectrum at the working currents are related to the frequency of hopping between deep centers near the InGaN/GaN QW and to Maxwell relaxation in the space-charge region.

Токовый шум и падение эффективности светодиодов при туннелировании носителей из квантовой ямы InGaN/GaN с участием дефектов

AbstractThe current dependences of the spectral noise density and quantum efficiency in green and blue light-emitting diodes with InGaN/GaN quantum wells (QWs) are measured. It is shown that the noise level greatly increases at high currents at which there is a quantum efficiency droop. The mechanism by which the current noise is formed is associated with hopping transport via the deep states of color centers in GaN across the n barrier of an InGaN/GaN QW. The source of the noise is the hopping resistance of the space-charge region, which limits the current of thermally activated electrons into the QW. The efficiency droop and the increase in noise level are attributed to a change in the electric-field direction near the QW at high injection levels and to an increase in the tunneling leakage of holes from the QW. It is shown that the experimental frequency-related noise spectra having the shape of a Lorentzian spectrum at the working currents are related to the frequency of hopping between deep centers near the InGaN/GaN QW and to Maxwell relaxation in the space-charge region.

PCR Analysis Methods for Detection and Identification of Beer-Spoilage Lactic Acid Bacteria.

Polymerase chain reaction (PCR) analysis enables rapid and accurate detection of beer-spoilage lactic acid bacteria (LAB). Hop resistance genes, horA and horC, are utilized as genetic markers to determine the spoilage ability of LAB strains. PCR analysis of horA and horC, combined with multiplex PCR methods of 12 beer-spoilage species, enables simultaneous and comprehensive detection easily and inexpensively.

A novel horA genetic mediated RCA detection of beer spoilage lactobacillus

As one of the most popular beverage, beer has strong resistance to bacteria except for lactic acid bacteria (LAB), as its strong viability in beer. Contaminating LAB results in beer spoilage. HorA gene carried by beer spoilage lactobacillus confers hop resistance and is associated with the growth of Lactobacillus in beer, thus can be used as a perfectly valid genetic marker for the detection of beer spoilage Lactobacillus strains. This study applied genome and bioinformatics analyses, together with genetic alignment and comparison techniques to build a rolling circle amplification (RCA) detection method targeted on horA for beer spoilage Lactobacillus. The horA genetic mediated RCA method showed rapid, sensitive and specific on beer spoilage lactobacillus detection.

Sporeforming bacteria in beer: Occurrence, diversity, presence of hop resistance genes and fate in alcohol-free and lager beers

The aim of this study was to assess the occurrence of sporeforming bacteria in different types of beers (n = 163) and to assess the presence of hor genes in the isolates. Additionally, the study aimed to evaluate the fate of five representative sporeforming bacteria harboring horA and horC genes in alcohol-free and lager beers. Two hundred and sixty (n = 260) sporeforming bacteria belonging to eight different genera were isolated from beers, i.e., Bacillus (n = 118), Paenibacillus (n = 89) and Brevibacillus (n = 41), Lysinbacillus (n = 6), Cohnella (n = 3), Rummeliibacillus (n = 1), Alicyclobacillus (n = 1), and Anoxybacillus (n = 1), respectively. A predominance of members within the Bacillus cereus sensu lato (n = 72; 27.1%), followed by B. megaterium (n = 18; 7%), P. validus (n = 16; 6.1%), P. humicus (n = 13; 5%), P. alginolyticus (n = 13; 5%) and Br. brevis (n = 13; 5%) was observed in beer samples analyzed. Only 5% (n = 14) out of 260 sporeforming bacterial isolates recovered from beers harbored one or both horA and horC genes. Only one (0.3%) isolate, i.e., Bacillus cereus sensu lato (identified as B. thuringiensis LMQA 206) presented both horA and horC genes. None of the five bacterial sporeforming strains harboring horA or horC genes inoculated was able to grow in the beers throughout the storage period studied, and no spoilage was detected. The results of this study indicated a widespread occurrence of sporeforming bacteria in several types of beers from different brands, highlighting that measures should be taken to reduce the occurrence of sporeforming bacteria considering stability and safety concerns.

Counterorienting the war on terror: Arab hip hop and diasporic resistance

Counterorienting the war on terror: Arab hip hop and diasporic resistance