Factors affecting Alicyclobacillus acidoterrestris growth and guaiacol production and controlling apple juice spoilage by lauric arginate and ϵ-polylysine

Variation of volatile compounds and sensory profile for Protaetia brevitarsis larvae fermented with lactic acid bacteria and yeast

This study aimed to investigate the correlation between the composition of volatile compounds, consumer acceptance, and drivers of (dis)liking of Protaetia brevitarsis larvae fermented using lactic acid bacteria and yeast. Volatile compounds were analyzed using HS-SPME-Arrow-GC-MS, and a sensory evaluation was conducted with 72 consumers. A total of 113 volatile compounds were detected, and principal component analysis indicated that the samples could be divided into three groups. The calculated relative odor activity values (ROAV) revealed the presence of 27 compounds (ROAV >1). Volatile compounds with high ROAV were predominantly found during yeast fermentation. The sensory evaluation results indicated a strong correlation between low levels of off-odor intensity and high odor liking, emphasizing that odor profile had a more direct association with consumer acceptance than odor intensity. These findings suggest that yeast fermentation using volatile compounds, which positively influences consumer acceptance, is appropriate for Protaetia brevitarsis larvae.

Biosafety measures for Alicyclobacillus spp. strains across various levels of biohazard

Alicyclobacillus bacteria are important contaminants in the beverage industry because their spores remain in the product after usual pasteurization. At the same time, their impact on human health has yet to be characterized, as it is generally assumed to be low or non-existent. However, these bacteria are causing quality concerns mainly due to odor and taste changes of the product. Since potential health effects are not precisely known, an experimental assessment was performed, including a biosafety assessment of six viable and non-viable vegetative and spore forms of Alicyclobacillus spp. strains using cell cultures and rodent study. The monolayer of Caco-2 (Cancer coli-2) cells was investigated for its adsorption effect on the epithelium of the small intestine of mice. Lactate dehydrogenase leakage (LDH) and transepithelial electrical resistance (TEER) tests were used to ensure the integrity of the cell membrane and tight junctions. The methylthiazole tetrazolium bromide (MTT) assay examined in vitro cytotoxicity in Caco-2 and HepG2 cell lines. The hemolysis of erythrocytes was spectrophotometrically measured. The results showed negligible cytotoxicity or non-toxic response in mice. In conclusion, Alicyclobacillus spp. exhibited biocompatibility with negligible cytotoxicity and minimal safety concerns.

Exploring the growth characteristics of Alicyclobacillus acidoterrestris for controlling juice spoilage with zero additives

Fruit juice spoilage that caused by contaminated Alicyclobacillus has brought huge losses to beverage industry worldwide. Thus, it is very essential to understand the growth and metabolism processing of Alicyclobacillus acidoterrestris (A. acidoterrestris) in controlling juice spoilage caused by Alicyclobacillus. In this work, simulative models for the growth and metabolism of A. acidoterrestris were systematically conducted in the medium and fruit juice. The results showed that low temperature (4 ℃) and strong acidic environment (pH 3.0-2.0) of medium inhibited the growth and reproduction of A. acidoterrestris. In addition, with decreasing temperature, the color, smell and turbidity of commercially available juice supplemented with A. acidoterrestris significantly improved. This work provided a clear exploration of growth characteristics of A. acidoterrestris by applying theory (medium) to reality (fruit juices), and pave fundamental for exploring the zero additives of controlling juice spoilage.

Electron coupling effect-triggered monatomic copper laccase-mimicking nanozyme for the degradation and detection of guaiacol produced by Alicyclobacillus acidoterrestris

The generation of guaiacol by Alicyclobacillus acidoterrestris (A. acidoterrestris) in fruit juices negatively affects public health and causes severe environmental pollution. Therefore, the sensitive detection and efficient degradation of guaiacol in real samples are crucial. Here, we develop an electrochemical sensor utilizing a copper single-atom nanozyme (CuN4-G) to detect and degrade guaiacol at the picomolar level. Density functional theory (DFT) calculations verify that the bonding electron coupling effect in the CuN4-G facilitates rapid electron transfer, enhances electrical conductivity, and provides abundant active sites, thereby leading to exceptional catalytic performance. Moreover, CuN4-G demonstrates a Km value similar to that of natural laccase but a higher Vmax, highlighting its potential as a highly efficient biocatalyst. The CuN4-G-based electrochemical sensor achieves a detection from 5 to 50,000 pM for guaiacol, with a 1.2 pM (S/N = 3) detection limit. Additionally, CuN4-G-modified electrodes display high selectivity and excellent stability. CuN4-G nanozyme can keep its activity in conditions of pH (3-9), temperature (30-90 °C), ionic strength (0-400 mM), and organic solvent (0-50% (v/v)), overcoming the deficiencies of natural enzymes. Furthermore, our electrochemical sensor can not only accurately detect guaiacol, but also degrade it in actual fruit juice samples infected by A. acidoterrestris, demonstrating its potential applications in food and environmental monitoring.

Effects of conjugates of ε-polylysine-dextran created through Maillard reaction on quality and storage stability of the chicken gel

The present study mainly focused on the effects of the conjugates of PL-dextran produced through the Maillard reaction on the quality and storage stability of chicken gel for 5 days at 4 ℃. According to the results of the texture profile, water retention capacity (WRC), low-field nuclear magnetic resonance (LF NMR), aerobic plate count (APC), and total volatile basic nitrogen (TVBN), ε-polylysine (PL) could improve chicken gel storage stability while decreasing the quality of protein gels (p < 0.05). Additionally, adding dextran with high or low molecular weight could significantly increase the quality of gel during storage (p < 0.05), whereas decreased storage stability could be obtained (p < 0.05). In general, conjugates formed by PL and dextran with high molecular weight were beneficial for quality maintenance. In comparison, the polymers produced from the low molecular weight of dextran could modify the storage stability of gels. Adding conjugates of dextran and PL benefited the structure formation of protein gel, while PL would retain part of antibacterial activity when crosslinked with dextran. Therefore, it could be concluded that the quality improvement effect of PL-dextran addition on gel quality was greater than its antibacterial effect, which would impact the formulation design of novel emulsion-type meat products.

Unveiling the complete genome sequence of Alicyclobacillus acidoterrestris DSM 3922T, a taint-producing strain

Several species from the Alicyclobacillus genus have received much attention from the food and beverages industries. Their presence has been co-related with spoilage events of acidic food matrices, namely fruit juices and other fruit-based products, the majority attributed to Alicyclobacillus acidoterrestris. In this work, a combination of short and long reads enabled the assembly of the complete genome of A. acidoterrestris DSM 3922T, perfecting the draft genome already available (AURB00000000), and revealing the presence of one chromosome (4,222,202 bp; GC content 52.3%) as well as one plasmid (124,737 bp; GC content 46.6%). From the 4,288 genes identified, 4,004 sequences were attributed to coding sequences with proteins, with more than 80% being functionally annotated. This allowed the identification of metabolic pathways and networks and the interpretation of high-level functions with significant reliability. Furthermore, the additional genes of interest related to spore germination, off-flavor production, namely the vdc cluster, and CRISPR arrays, were identified. More importantly, this is the first complete and closed genome sequence for a taint-producing Alicyclobacillus species and thus represents a valuable reference for further comparative and functional genomic studies.

Recent advances in structural characterization of biomacromolecules in foods via small-angle X-ray scattering

Small-angle X-ray scattering (SAXS) is a method for examining the solution structure, oligomeric state, conformational changes, and flexibility of biomacromolecules at a scale ranging from a few Angstroms to hundreds of nanometers. Wide time scales ranging from real time (milliseconds) to minutes can be also covered by SAXS. With many advantages, SAXS has been extensively used, it is widely used in the structural characterization of biomacromolecules in food science and technology. However, the application of SAXS in charactering the structure of food biomacromolecules has not been reviewed so far. In the current review, the principle, theoretical calculations and modeling programs are summarized, technical advances in the experimental setups and corresponding applications of in situ capabilities: combination of chromatography, time-resolved, temperature, pressure, flow-through are elaborated. Recent applications of SAXS for monitoring structural properties of biomacromolecules in food including protein, carbohydrate and lipid are also highlighted, and limitations and prospects for developing SAXS based on facility upgraded and artificial intelligence to study the structural properties of biomacromolecules are finally discussed. Future research should focus on extending machine time, simplifying SAXS data treatment, optimizing modeling methods in order to achieve an integrated structural biology based on SAXS as a practical tool for investigating the structure-function relationship of biomacromolecules in food industry.

Effects of Fruit Storage Temperature and Time on Cloud Stability of Not from Concentrated Apple Juice

Apple juice that is designated ‘Not from concentrated’ (NFC) is now increasingly popular with consumers due to its unique taste and rich nutritional value. However, layered precipitation and instability have emerged as serious technical problems that restrict the viability of the NFC apple juice industry. This study researched the influence of water-cored ‘Fuji’ apple fruit storage under different temperatures (0, 20 °C) and times (0, 9, 18, 30, 60 days) on the turbidity stability of NFC apple juice. Changes in the physicochemical properties (juice yield, pH, total soluble solids and titratable acid), turbidity stability (turbidity and particle size) and precipitation sensitive substances (insoluble starch, total phenolics, soluble protein and pectin) of NFC apple juice were determined, combined with the respiratory rates and ethylene release of apples, in order to study post-harvest regulation and control of processed fruit. Results indicated that fruit storage temperature and time significantly guided the turbidity stability of NFC apple juice. As a typical respiratory climacteric fruit, apple fruit stored 45 days at 0 °C and 15 days at 20 °C gained the best juice stability, respectively. This is basically consistent with the respiratory peak of fruit when processing raw materials. During the post-ripening process, the insoluble starch in apple gradually hydrolyzed into fructose and glucose, while total phenolics diminished and water-soluble pectin content increased. On the other hand, the amounts of pectin, soluble protein and phenolics in fruit juice declined as the fruit aged in the late storage period (stored 75 days at 0 °C and 40 days at 20 °C). Meanwhile particle size became larger and the turbidity stability of cloudy juices also decreased. This study’s results will provide a sound theoretical basis for improving the turbidity stability of NFC apple juice by regulating the physiological state of processed raw materials.

Headspace control and antimicrobials: inhibition strategies to prevent growth of Alicyclobacillus acidoterrestris in orange juice

Alicyclobacillus acidoterrestris can cause spoilage in orange juice that leads to consumer rejection. Six different orange juices were physiochemically characterized (pH, total soluble solids, titratable acidity, total polyphenols and vitamin C). A bottle for each sampling point per juice was filled (headspace: 40% volume) and inoculated with 10² - 10³ CFU ml^-1 of A. acidoterrestris ATCC® 49025™ (heat shocked before inoculation: 75°C, 20 min). Samples were stored for 21 d at 45 ± 1°C and plate counted periodically on acidified YSG agar (pH 3.7) incubated at 45 ± 1°C for 3 d. The effect of headspace (6% versus 40% volume) on A. acidoterrestris growth was also evaluated. The effect of nisin (0.006%, 0.003%, 0.0015%, and 0.00075%), sodium benzoate (0.1%), potassium sorbate (0.1%), and a mix of benzoate and sorbate (0.05% each) on A. acidoterrestris was additionally addressed. A. acidoterrestris reached up to 10⁷ CFU ml^-1 in five of the six juices in less than one week. Headspace significantly impacted (P<0.05) A. acidoterrestris maximum population, which reached the critical value of 5 log CFU ml^-1 at 40% headspace. All preservatives, regardless of concentration, showed a bacteriostatic effect during 22 d of storage with no significant differences among treatments (P>0.05).

The Role of Epigenetic Modifications in Human Cancers and the Use of Natural Compounds as Epidrugs: Mechanistic Pathways and Pharmacodynamic Actions

Cancer is a complex disease resulting from the genetic and epigenetic disruption of normal cells. The mechanistic understanding of the pathways involved in tumor transformation has implicated a priori predominance of epigenetic perturbations and a posteriori genetic instability. In this work, we aimed to explain the mechanistic involvement of epigenetic pathways in the cancer process, as well as the abilities of natural bioactive compounds isolated from medicinal plants (flavonoids, phenolic acids, stilbenes, and ketones) to specifically target the epigenome of tumor cells. The molecular events leading to transformation, angiogenesis, and dissemination are often complex, stochastic, and take turns. On the other hand, the decisive advances in genomics, epigenomics, transcriptomics, and proteomics have allowed, in recent years, for the mechanistic decryption of the molecular pathways of the cancerization process. This could explain the possibility of specifically targeting this or that mechanism leading to cancerization. With the plasticity and flexibility of epigenetic modifications, some studies have started the pharmacological screening of natural substances against different epigenetic pathways (DNA methylation, histone acetylation, histone methylation, and chromatin remodeling) to restore the cellular memory lost during tumor transformation. These substances can inhibit DNMTs, modify chromatin remodeling, and adjust histone modifications in favor of pre-established cell identity by the differentiation program. Epidrugs are molecules that target the epigenome program and can therefore restore cell memory in cancerous diseases. Natural products isolated from medicinal plants such as flavonoids and phenolic acids have shown their ability to exhibit several actions on epigenetic modifiers, such as the inhibition of DNMT, HMT, and HAT. The mechanisms of these substances are specific and pleiotropic and can sometimes be stochastic, and their use as anticancer epidrugs is currently a remarkable avenue in the fight against human cancers.

Fabrication of Epsilon-Polylysine-Based Magnetic Nanoflowers with Effective Antibacterial Activity against Alicyclobacillus acidoterrestris

The risk of fruit juice contamination caused by microorganisms, especially Alicyclobacillus acidoterrestris, has been reported worldwide. To develop cost-effective control methods, in this work, flower-like magnetic molybdenum disulfide (Fe₃O₄@MoS₂) nanoparticles (NPs) were fabricated by a facile two-step hydrothermal method. After further modifying polyacrylic acid (PAA) on the surface of the NPs, epsilon-polylysine (EPL) was immobilized via N-(3-dimethylaminopropyl)-N-carbodiimide hydrochloride/N-hydroxysuccinimide coupling reaction to obtain the Fe₃O₄@MoS₂@PAA-EPL nanocomposites. Antibacterial results exhibited that the synthesized nanocomposites showed effective antibacterial activity against A. acidoterrestris with a minimum inhibitory concentration of 0.31 mg mL^-1. Investigation on the antibacterial mechanism revealed that the presence of nanocomposites caused damage and disruption of the bacterial membrane through dent formation, resulting in the leakage of intracellular protein. Moreover, the activity of dehydrogenase enzymes was inhibited with the treatment of Fe₃O₄@MoS₂@PAA-EPL, causing the reduction of metabolic activity and adenosine triphosphate levels in bacteria. Simultaneously, the presence of nanocomposites improved intracellular reactive oxygen species levels, and this disrupted the antioxidant defense system and caused oxidative damage to bacteria. Furthermore, Fe₃O₄@MoS₂@PAA-EPL nanocomposites were confirmed to possess satisfactory biocompatibility by performing in vitro cytotoxicity and in vivo acute toxicity experiments. The aim of this research was to develop a new pathway for the inhibition of A. acidoterrestris in the juice industry.

Detection and characterization of a rare two-component lantibiotic, amyloliquecidin GF610 produced by Bacillus velezensis, using a combination of culture, molecular and bioinformatic analyses

AIM

To detect and characterize novel lantibiotics from a collection of Bacillus spp. using a multifaceted analytical approach.

METHODS AND RESULTS

A previously completed microassay identified 45 Bacillus isolates with anti-Listeria activity. The isolates were PCR screened using degenerate primers targeting conserved sequences in lanM-type lantibiotics. B. velezensis GF610 produced a PCR product whose sequence, along with genome mining and bioinformatics, guided the liquid chromatographic analysis of strain's cell-free extracts and the mass spectrometry of purified fractions. Results revealed a new amyloliquecidin variant (designated GF610) produced by the strain. Amyloliquecidin GF610 is a two-component lantibiotic with α and β peptides having monoisotopic masses of 3026 and 2451 Da, and molecular formulae C₁₃₀ H₁₉₁ N₃₅ O₃₉ S₅ and C₁₁₀ H₁₅₈ N₂₆ O₃₀ S₄ , respectively. Amyloliquecidin GF610 is active against Listeria monocytogenes, Clostridium sporogenes, Clostridioides difficile, Staphylococcus aureus and Alicyclobacillus acidoterrestris with minimum inhibitory concentrations (MICs) in the range of 0.5-7.0 µmol l^-1 .

CONCLUSIONS

The proposed multifaceted analytical approach was valuable to provide a deep and proper characterization of a novel bacteriocin, amyloliquecidin GF610, with high antimicrobial activity against Gram-positive bacteria.

SIGNIFICANCE AND IMPACT

The discovered Amyloliquecidin GF610 is potentially useful in food, agricultural or medical applications. The analytical approach followed may facilitate future discoveries of two-component lantibiotics, which are challenging compounds to detect and characterize.

Epsilon-polylysine based magnetic nanospheres as an efficient and recyclable antibacterial agent for Alicyclobacillus acidoterrestris

In this work, polyacrylic acid modified ferroferric oxide (Fe₃O₄-PAA) was synthesized via a one-step hydrothermal method. The magnetic nanospheres modified with carboxyl groups were combined with epsilon-polylysine (EPL) via an EDC/NHS coupling reaction to obtain Fe₃O₄-PAA-EPL nanospheres. Fe₃O₄-PAA-EPL was employed as an antibacterial agent against Alicyclobacillus acidoterrestris and characterized by XRD, FTIR, XPS, VSM, SEM and TEM techniques. Experimental results showed the minimum inhibition concentration (MIC) of Fe₃O₄-PAA-EPL against A. acidoterrestris was 1.25 mg mL^-1. Furthermore, A. acidoterrestris treated with Fe₃O₄-PAA-EPL nanospheres obviously lysed. Morphological analysis of bacteria supported by SEM indicated that the cell membrane of A. acidoterrestris was damaged, revealing that Fe₃O₄-PAA-EPL is an effective antibacterial agent. Additionally, the nanospheres with excellent magnetism can be simply separated from a reaction system via an external magnet. The construction of magnetic nanospheres with satisfactory antibacterial activity provides an effective and new method to control A. acidoterrestris.

Complex coacervation of food grade antimicrobial lauric arginate with lambda carrageenan

In this study, the complex coacervation mechanism of Lauric arginate ester (LAE) with λ-carrageenan was studied using turbidimetry, light scattering and electrophoresis. The complexes formed were found to have a bilayer-like structure using small angle X-ray scattering (SAXS) and cryo-TEM (transmission electron microscopy). It was observed that mixing LAE with Sodium dodecyl sulfate (SDS) could significantly reduce the interactions between mixed micelles and λ-carrageenan. The interactions between LAE/SDS and λ-carrageenan were found to be predominantly entropy driven. Mixed micelles of LAE/Tween 20 and LAE/SDS showed significantly less interactions with carrageenan compared to pure LAE micelles. Interfacial properties of complexes were measured using surface tension measurements. It was observed that pure LAE showed good foaming behavior and when mixed with increasing amounts of carrageenan the foaming capacity decreased. Reduction in foam volume was due to reduced availability of free LAE molecules for foam stabilization and due to hydrophilic nature of complexes.

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Lauric arginate forms complex coacervates with Lambda carrageenan due to combination of electrostatic and hydrophobic interactions.

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Coacervation leads to both soluble and insoluble coacervates depending on the mixing ratio.

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The complex coacervates show a lamellar microstructure with certain degree of disorder in the lamellar layers.

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Interactions of Lauric arginate with Lambda carrageenan decrease when it is mixed with either non ionic or anionic surfactant due to formation of mixed micelles.