Decarboxylase Activity Research Articles

CsAlaDC and CsTSI work coordinately to determine theanine biosynthesis in tea plants (Camellia sinensis L.) and confer high levels of theanine accumulation in a non-tea plant.

Theanine, one of the most important components of teas, confers the umami taste and relaxation effect of tea infusion. As a non-proteinogenic amino acid, theanine solely accumulates to high levels in tea plants (Camellia sinensis L.); however, the underlying mechanism remains largely unknown. Theanine is biosynthesized from ethylamine and glutamate by CsTSI (Theanine Synthetase I), with ethylamine being synthesized from alanine, by alanine decarboxylase. Although CsAlaDC exhibited alanine decarboxylase activity, in vitro, the in vivo role in tea plants has not been characterized. In this study, we found ethylamine content in tea roots to be highly correlated with theanine content (r=0.883, p <0.01), and expression levels of CsAlaDC were similarly highly correlated with the accumulation of ethylamine (r=0.903, p <0.01) and theanine (r=0.881, p <0.01). CsAlaDC-expressing tobacco leaves produced high levels of ethylamine, but did not produce detectable theanine. However, high levels of theanine were produced in leaves co-expressing CsAlaDC and CsTSI. These results indicate CsAlaDC and CsTSI act coordinately in determining the high level of theanine biosynthesis. This is also the first report to synthesize theanine in a non-tea plant, which offers the potential to generate relaxation-promoting foods by synthesizing theanine in crops.

Characterization of metabolic pathways for biosynthesis of the flavor compound 3-methylbutanal by Lactococcus lactis

3-Methylbutanal is a key volatile compound that imparts a nutty flavor to Cheddar cheese. Lactococcus lactis has been successfully applied as a starter to increase the level of 3-methylbutanal produced during the ripening of cheese. However, the mechanism of action and genetic diversity of this bacterium for 3-methylbutanal biosynthesis remains unclear. In this study, we investigated the association between the L. lactis genotype and phenotype in the biosynthesis of 3-methylbutanal via both direct and indirect pathways. Fourteen strains of L. lactis were screened for the capacity to produce 3-methylbutanal, and strain 408 (>140 μM) produced the highest among all tested strains, which exhibited both α-keto acid decarboxylase and α-ketoacid dehydrogenase activities. Furthermore, the results of a sodium meta-arsenite inhibition experiment showed that the 3-methylbutanal-producing capacities of each strain declined to various degrees. The kdcA gene, which encodes the direct pathway component α-ketoacid decarboxylase, was detected in 4 of the 14 strains, of which only strain 408 contained the full-length gene. We then characterized the genes associated with the indirect pathway by detecting the expression levels of the pdh gene cluster, ack, and pta, which were expressed at relatively higher levels in a high-yield strain than in a low-yield strain. As a result, these L. lactis strains were divided into 3 categories according to gene diversity, gene expression, and 3-methylbutanal production. The results of this study refine our knowledge of the genetic determinants of 3-methylbutanal biosynthesis in L. lactis and explain the effect of both synthesis pathways on 3-methylbutanal production.

Cell Proliferation and Tumor Induction by Ochratoxin A in Mouse Skin and Evaluation of Cyclin D1 and Cyclooxygenase-2 Expressions.

Motivation. Skin tumor is one of the frequent occurring forms of cancer where 2-3 million instances are reported worldwide. The ultraviolet rays along with the environmental pollutants and other contaminants can be the potential factors of skin cancer. Cyclin D1 is a serious gene included in controlling the development through the G1 phase of the cell cycle. Ochratoxin A (OTA) is a naturally existing mycotoxin which majorly occurs in food like grains. It is responsible for producing the splitting of single-strand DNA and is identified to be cancer-causing. It is established as a critical risk factor towards reproductive health in both males and females. Methodology. A single dose of ochratoxin A was used for topical application for assessment of skin tumor promotion activity, hyperplasia, ornithine decarboxylase activity, and expression of cyclin D1 and COX-2 in mouse skin. Enhancement in the synthesis of DNA, activation of the epidermal growth factor receptor, and overexpression of cyclin D1 and COX-2 were noted. Primary murine keratinocyte cell culture was cultured with Waymouth's medium. Western blot analysis and real-time polymerase chain reaction (RT-PCR) were used to detect the expression of cyclin D1 and COX-2. Chromatin immunoprecipitation (ChIP) assays were used to the association between AP-1 transcription and nuclear factor-kappaB (NF-κB) with COX-2 and cyclin D1 promoters. Results. The results found that cyclin D1 and COX-2 were responsible for stimulating OTA-induced PMK proliferation and hyperplasia. Implications. EGFR-mediated pathways were also responsible for tumor promotion due to OTA.

S2631 Porphyria Cutanea Tarda, Type 2, in a Man With a Novel UROD Mutation

Introduction: Porphyria cutanea tarda (PCT) is usually caused by acquired defects in uroporphyrinogen decarboxylase (UROD) activity in the liver. 20% of cases occur in patients who have a genetically determined partial decrease in UROD activity. We describe a case of a man with a novel UROD mutation causing PCT type 2. Case Description/Methods: A 77-year-old man was evaluated for 6 months of painful blistering over his dorsal hands, forearms and head [Fig 1a]. His medical history was notable for hypertension, melanoma, and stroke. He reported heavy alcohol and tobacco use. He had no family history of porphyria. He worked for years at a manufacturing facility, with exposure to various industrial chemicals. More recently, he had exposure to weed killers, carburetor cleaners, and wood varnish. Exam revealed tense bullae with milia and hyperpigmented macules on dorsal hands and forearms. Biopsies revealed a subepidermal blister containing a small number of neutrophils with fibrin and evidence of festooning of the vessels consistent with porphyria. Labs revealed AST 63 U/L, ALT 64 U/L, alkaline phosphatase 54 U/L, and total bilirubin 0.8 mg/dL. Iron profile was unremarkable, and antibodies against HIV and hepatitis A, B and C were negative. Total plasma porphyrins were elevated to 13.4 mcg/dL. Fractionated urine, stool and plasma porphyrin levels were obtained [Table 1]. Urinary uro- and hepta-carboxyl porphyrins were markedly elevated, consistent with PCT. The patient was advised to start hydroxychloroquine 100 mg 3 times weekly and to avoid alcohol, tobacco use and sun exposure. Genetic testing revealed a novel mutation of UROD gene (c.224 G >C; p. Arg 75 Pro) with red blood cell UROD activity decreased by 50%. He returned to clinic 3 and 7 months after the index visit. He had stopped alcohol use, but continued smoking cigarettes. His hands were improved [Fig 1b]. Repeat urinary porphyrins showed improvement [Table 1]. The mutation in UROD is predicted to have a major effect on protein structure and function [Fig 1c]. Discussion: Inherited partial deficiency in UROD is not sufficient to cause clinically manifest PCT. Other factors that increase oxidative stress are also required. This patient has a mutation in the UROD gene not heretofore described in PCT type 2, but that we show markedly affects the structure and activity of the protein product. Nonetheless, the patient did not develop clinically manifest PCT until age 77, emphasizing the importance of acquired factors in disease pathogenesis.Figure 1.: A. Dorsal right hand at presentation B. Dorsal right hand at 7 month follow-up C. Structure of URO-D showing the substrate (yellow) in the active site located at the C-terminal end of the beta-sheets (magenta) that form the core of the TIM-barrel structure. The location of arginine 75 (Arg 75) is shown in green. Arg 75 is the penultimate residue in one of the eight corresponding alpha-helices that surround the central core. Arg 75 forms two hydrogen bonds with glutamic acid 45 (Glu 45) of the preceding helix in the structure. This hydrogen bonding network supports the overall tertiary fold of the protein in this otherwise solvent-exposed region of the protein. The UROD mutation of the patient (Arg 75 Pro) disrupts the helix with premature termination and more importantly eliminates the hydrogen bonding network.Table 1-A.: Results of Selected Laboratory Studies.Table 1-B.: Results of Selected Laboratory Studies.

Hyperglycemic conditions proliferate triple negative breast cancer cells: role of ornithine decarboxylase

Several cancer subtypes (pancreatic, breast, liver, and colorectal) rapidly advance to higher aggressive stages in diabetes. Though hyperglycemia has been considered as a fuel for growth of cancer cells, pathways leading to this condition are still under investigation. Cellular polyamines can modulate normal and cancer cell growth, and inhibitors of polyamine synthesis have been approved for treating colon cancer, however the role of polyamines in diabetes-mediated cancer advancement is unclear as yet. We hypothesized that polyamine metabolic pathway is involved with increased proliferation of breast cancer cells under high glucose (HG) conditions. Studies were performed with varying concentrations of glucose (5-25mM) exposure in invasive, triple negative breast cancer cells, MDA-MB-231; non-invasive, estrogen/progesterone receptor positive breast cancer cells, MCF-7; and non-tumorigenic mammary epithelial cells, MCF-10A. There was a significant increase in proliferation with HG (25mM) at 48-72h in both MDA-MB-231 and MCF-10A cells but no such effect was observed in MCF-7 cells. This was correlated to higher activity of ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine synthesis pathway. Inhibitor of polyamine synthesis (difluoromethylornithine, DFMO, 5mM) was quite effective in suppressing HG-mediated cell proliferation and ODC activity in MDA-MB-231 and MCF-10A cells. Polyamine (putrescine) levels were significantly elevated with HG treatment in MDA-MB-231 cells. HG exposure also increased the metastasis of MDA-MB-231 cells. Our cellular findings indicate that polyamine inhibition should be explored in patient population as a target for future chemotherapeutics in diabetic breast cancer.

Acid resistance system CadBA is implicated in acid tolerance and biofilm formation and is identified as a new virulence factor of Edwardsiella tarda

Edwardsiella tarda is a facultative intracellular pathogen in humans and animals. The Gram-negative bacterium is widely considered a potentially important bacterial pathogen. Adaptation to acid stress is important for the transmission of intestinal microbes, so the acid-resistance (AR) system is essential. However, the AR systems of E. tarda are totally unknown. In this study, a lysine-dependent acid resistance (LDAR) system in E. tarda, CadBA, was characterized and identified. CadB is a membrane protein and shares high homology with the lysine/cadaverine antiporter. CadA contains a PLP-binding core domain and a pyridoxal phosphate-binding motif. It shares high homology with lysine decarboxylase. cadB and cadA are co-transcribed under one operon. To study the function of the cadBA operon, isogenic cadA, cadB and cadBA deletion mutant strains TX01ΔcadA, TX01ΔcadB and TX01ΔcadBA were constructed. When cultured under normal conditions, the wild type strain and three mutants exhibited the same growth performance. However, when cultured under acid conditions, the growth of three mutants, especially TX01ΔcadA, were obviously retarded, compared to the wild strain TX01, which indicates the important involvement of the cadBA operon in acid resistance. The deletion of cadB or cadA, especially cadBA, significantly attenuated bacterial activity of lysine decarboxylase, suggesting the vital participation of cadBA operon in lysine metabolism, which is closely related to acid resistance. The mutations of cadBA operon enhanced bacterial biofilm formation, especially under acid conditions. The deletions of the cadBA operon reduced bacterial adhesion and invasion to Hela cells. Consistently, the deficiency of cadBA operon abated bacterial survival and replication in macrophages, and decreased bacterial dissemination in fish tissues. Our results also show that the expression of cadBA operon and regulator cadC were up-regulated upon acid stress, and CadC rigorously regulated the expression of cadBA operon, especially under acid conditions. These findings demonstrate that the AR CadBA system was a requisite for the resistance of E. tarda against acid stress, and played a critical role in bacterial infection of host cells and in host tissues. This is the first study about the acid resistance system of E. tarda and provides new insights into the acid-resistance mechanism and pathogenesis of E. tarda.

Quality formation of germination brown rice under microwave drying: from GABA content to color value

In order to improve the final quality of germination brown rice (GBR), the changes of GBR in Gamma-aminobutyric acid (GABA) and color are investigated under microwave drying conditions. Results indicate that Microwave drying process may improve GABA in GBR due to microwave volumetric heating inducing the glutamic acid decarboxylase (GAD) activity; and the dried GBR with golden appearance under the microwave intensity of 2.75 W/g and the apparent velocity of 2.50 m/s considering the drying efficiency and quality of dried GBR. In this study, microwave drying conditions not only improve the drying efficiency of GBR, but also improve the appearance and color of GBR after drying, reduce GABA degradation and control the generation of burst rate.

Optimization of γ-Aminobutyric Acid (GABA) Accumulation in Germinating Adzuki Beans (Vigna angularis) by Vacuum Treatment and Monosodium Glutamate, and the Molecular Mechanisms.

This study aimed to investigate the optimal hypoxic and monosodium glutamate (MSG) stress conditions for the enrichment of γ-Aminobutyric acid (GABA) in germinating adzuki beans and to reveal the potential underlying molecular mechanisms of GABA accumulation. Using single-factor experiments and response surface model, we investigated the effects of germination time, germination temperature, vacuum time, and MSG concentration on GABA contents, and further explored the activity and gene expression of glutamate decarboxylase (GAD) and polyamine oxidase (PAO) critical rate restriction enzymes during GABA synthesis. The optimal soaking temperature, soaking time, and pH conditions were 35°C, 16 h, and 5, respectively. Furthermore, the optimal germination conditions for optimal GABA enrichment were 48 h, 1.99 mg/ml MSG concentration, germination temperature of 31.49°C, and vacuum time of 15.83 h. Under such conditions, the predicted GABA concentration was 443.57 ± 7.18 mg/100 g, with no significant difference between the predicted and experimental data. The vacuum + MSG (FZM) treatment has a maximum contribution rate of GABA to 38.29%, which significantly increase GABA content, and the increase was associated with increased GAD and PAO activity. In addition, MSG in combination with vacuum treatment could significantly induce VaGAD4 and VaGAD6 genes in 2 days germination of adzuki beans. According to the results of the present study, vacuum + MSG treatment is an effective approach to enhancing GABA accumulation in germinating adzuki beans, which could be employed in enhancing the functional quality of germinating adzuki beans.

Directed evolution of prenylated FMN-dependent Fdc supports efficient in vivo isobutene production

Isobutene is a high value gaseous alkene used as fuel additive and a chemical building block. As an alternative to fossil fuel derived isobutene, we here develop a modified mevalonate pathway for the production of isobutene from glucose in vivo. The final step in the pathway consists of the decarboxylation of 3-methylcrotonic acid, catalysed by an evolved ferulic acid decarboxylase (Fdc) enzyme. Fdc belongs to the prFMN-dependent UbiD enzyme family that catalyses reversible decarboxylation of (hetero)aromatic acids or acrylic acids with extended conjugation. Following a screen of an Fdc library for inherent 3-methylcrotonic acid decarboxylase activity, directed evolution yields variants with up to an 80-fold increase in activity. Crystal structures of the evolved variants reveal that changes in the substrate binding pocket are responsible for increased selectivity. Solution and computational studies suggest that isobutene cycloelimination is rate limiting and strictly dependent on presence of the 3-methyl group.

Citronellal suppress the activity of ornithine decarboxylase in hypopharyngeal carcinoma cells

Citronellal, an acyclic monoterpene with an aldehyde group, is present in many plants, including species of Eucalyptus, Corymbia, Cymbopogon, Coriandrum. It is also known as rhodinol and possesses strong insect repellant and antifungal properties. In this study, we investigated the antiproliferative action of citronellal on hypopharyngeal carcinoma (FaDu) and normal (HEK-293) cell lines. Citronellal suppresses the activity of ornithine decarboxylase (ODC: 77.12±10.73 µM) and inhibits the proliferation of FaDu cells with an IC50 of 71.81±3.37 µM. The qRT-expression analysis depicts citronellal down-regulate the expression of ODC, and a robust binding interaction of citronellal with ODC was observed in molecular docking studies. Further, it also arrests the G2/M phase of FaDu cells, followed by an increase in the number of sub-diploid cells but was non-toxic to normal cell line. The toxicity prediction studies revealed citronellal follows the Lipinski rule of 5 and the Ghose rule. These observations provide experimental evidence for citronellal to be used as a new prototype for designing ODC inhibitors.

Muscimol Directly Activates the TREK-2 Channel Expressed in GABAergic Neurons through Its N-Terminus.

The two-pore domain K+ (K2P) channel, which is involved in setting the resting membrane potential in neurons, is an essential target for receptor agonists. Activation of the γ-aminobutyric acid (GABA) receptors (GABAAR and GABABR) reduces cellular excitability through Cl- influx and K+ efflux in neurons. Relatively little is known about the link between GABAAR and the K+ channel. The present study was performed to identify the effect of GABAR agonists on K2P channel expression and activity in the neuroblastic B35 cells that maintain glutamic acid decarboxylase (GAD) activity and express GABA. TASK and TREK/TRAAK mRNA were expressed in B35 cells with a high level of TREK-2 and TRAAK. In addition, TREK/TRAAK proteins were detected in the GABAergic neurons obtained from GABA transgenic mice. Furthermore, TREK-2 mRNA and protein expression levels were markedly upregulated in B35 cells by GABAAR and GABABR agonists. In particular, muscimol, a GABAAR agonist, significantly increased TREK-2 expression and activity, but the effect was reduced in the presence of the GABAAR antagonist bicuculine or TREK-2 inhibitor norfluoxetine. In the whole-cell and single-channel patch configurations, muscimol increased TREK-2 activity, but the muscimol effect disappeared in the N-terminal deletion mutant. These results indicate that muscimol directly induces TREK-2 activation through the N-terminus and suggest that muscimol can reduce cellular excitability by activating the TREK-2 channel and by inducing Cl- influx in GABAergic neurons.

Optimization of a cucurbit[6]uril-based real-time label-free method for analyzing the activity of ornithine decarboxylase

Ornithine decarboxylase (ODC) is a key enzyme in the biosynthetic pathway of polyamines and catalyzes the decarboxylation of ornithine to produce putrescine. Inhibition of ODC activity is a potential approach for the prevention and treatment of many diseases including cancer, as the expression levels and the activities of ODC in many abnormal cells and tumor cells are generally higher than those of normal cells. The discovery and evaluation of ODC inhibitors rely on the monitoring of the reaction processes catalyzed by ODC. There are several commonly used methods for analyzing the activity of ODC, such as measuring the yield of putrescine by high performance liquid chromatography, or quantifying the yield of isotope labelled carbon dioxide. However, the cumbersome operation and cost of these assays, as well as the difficulty to achieve high-throughput and real-time detection, hampered their applications. In this work, we optimized a real-time label-free method for analyzing the activity of ODC based on the macromolecule cucurbit[6]uril (CB6) and a fluorescent dye, DSMI (trans-4-[4-(dimethylamino) styryl]-1-methylpyridinium iodide). Finally, the optimized method was used to determine the activities of different ODC inhibitors with different inhibition mechanisms.

CaM enhances chilling tolerance of peach fruit by regulating energy and GABA metabolism

The effects of calcium chloride (CaCl2), calmodulin antagonist trifluoperazine (TFP) and different storage temperatures on chilling injury (CI) of peach fruit during postharvest storage were studied. The results showed that 0 ℃ storage and CaCl2 treatment reduced the CI index, reduced the ion leakage and maintained the integrity of cell membrane. Storage at 0 ℃ and CaCl2 treatment increased calmodulin (CaM) expression and protein content, energy charge (EC), adenosine triphosphate (ATP) content and adenosine diphosphate (ADP) content. At the same time, it also promoted the expression and activity of Ca2+-ATPase and other enzymes related to energy metabolism. In addition, storage at 0 ℃ and CaCl2 treatment promoted the expression and activity of glutamic acid decarboxylase (GAD), and increased the content of γ-aminobutyric acid (GABA) and the expression of GABA transaminase (GABA-T). On the contrary, TFP treatment significantly increased CI index and ion leakage, significantly inhibited PpCaM expression and protein content, and decreased EC and GABA content. Moreover, the molecular properties of PpCaM were studied. The results showed that PpCaM was a highly conserved hydrophilic protein, located on the nucleus and plasma membrane. PpCaM could induce the expression of PpCa2+-ATPase, increase the activity of Ca2+-ATPase, and participate in the regulation of energy metabolism. In addition, PpCaM could activate the activity of PpGAD, promote the synthesis of GABA, and participate in the regulation of GABA metabolism. These results suggested that 0 ℃ storage and CaCl2 treatment promoted the expression of PpCaM and increased the protein content of PpCaM, suggesting PpCaM enhanced the cold resistance and reduced the occurrence of CI by participating in the regulation of energy metabolism and GABA metabolism.

In-Cell Crosslinked Enzymes: Improving Bacillus megaterium whole-cell biocatalyst stability for the decarboxylation of ferulic acid

In-Cell Crosslinked Enzymes (InCLEs) is a procedure to improve the thermal and operational stability of Bacillus megaterium intracellular decarboxylase activity, allowing to obtain enhanced whole-cell biocatalyst to produce 4-vinyl guaiacol (4VG). InCLEs were achieved using a fixed amount of biomass in a two-step procedure: 1) permeation of the membrane cell for reactants diffusion, and 2) intracellular proteins crosslinking. To optimize InCLEs preparation, 7.68 mg of biomass in the presence of different ethanol concentrations (10–50% v/v) were permeated, subsequently, the intracellular proteins were crosslinked with a glutaraldehyde/biomass ratios of 0, 1.63 and 3.26 μmol/mg. At the best conditions (10% v/v ethanol and 1.63 μmol/mg), thermostability increases 4.7-fold against the permeated uncrosslinked biocatalyst (PUCB). To further enhance the stability, the internalization of different molecular weight polyethyleneimine (PEI, 1.09 mg/mL) was evaluated. PEI-InCLEs using 25 kDa PEI, showed a half-life 68-fold higher than PUCB (1 min) at 50 °C. After 7 cycles (26.3 mM ferulic acid, pH 7), PEI-InCLEs retained 83 and 69% of the decarboxylase activity at 40 and 50 °C, producing 32.7 and 29.8 μmol of 4VG, respectively. Here we demonstrated that the InCLEs procedure is an effective strategy to obtain stable whole-cell biocatalysts for the production of high-valued biotechnological molecules.

Non-Saccharomyces as Biotools to Control the Production of Off-Flavors in Wines.

Off-flavors produced by undesirable microbial spoilage are a major concern in wineries, as they affect wine quality. This situation is worse in warm areas affected by global warming because of the resulting higher pHs in wines. Natural biotechnologies can aid in effectively controlling these processes, while reducing the use of chemical preservatives such as SO2. Bioacidification reduces the development of spoilage yeasts and bacteria, but also increases the amount of molecular SO2, which allows for lower total levels. The use of non-Saccharomyces yeasts, such as Lachancea thermotolerans, results in effective acidification through the production of lactic acid from sugars. Furthermore, high lactic acid contents (>4 g/L) inhibit lactic acid bacteria and have some effect on Brettanomyces. Additionally, the use of yeasts with hydroxycinnamate decarboxylase (HCDC) activity can be useful to promote the fermentative formation of stable vinylphenolic pyranoanthocyanins, reducing the amount of ethylphenol precursors. This biotechnology increases the amount of stable pigments and simultaneously prevents the formation of high contents of ethylphenols, even when the wine is contaminated by Brettanomyces.

Effect of Non-thermal Atmospheric Plasma on Viability and Histamine-Producing Activity of Psychotrophic Bacteria in Mackerel Fillets.

Non-thermal atmospheric plasma (NTAP) has gained attention as a decontamination and shelf-life extension technology. In this study its effect on psychrotrophic histamine-producing bacteria (HPB) and histamine formation in fish stored at 0–5°C was evaluated. Mackerel filets were artificially inoculated with Morganella psychrotolerans and Photobacterium phosphoreum and exposed to NTAP to evaluate its effect on their viability and the histidine decarboxylase (HDC) activity in broth cultures and the accumulation of histamine in fish samples, stored on melting ice or at fridge temperature (5°C). NTAP treatment was made under wet conditions for 30 min, using a dielectric barrier discharge (DBD) reactor. The voltage output was characterized by a peak-to-peak value of 13.8 kV (fundamental frequency around 12.7 KHz). This treatment resulted in a significant reduction of the number of M. psychrotolerans and P. phosphoreum (≈3 log cfu/cm2) on skin samples that have been prewashed with surfactant (SDS) or SDS and lactic acid. A marked reduction of their histamine-producing potential was also observed in HDC broth incubated at either 20 or 5°C. Lower accumulation of histamine was observed in NTAP-treated mackerel filets that have been inoculated with M. psychrotolerans or P. phosphoreum and pre-washed with either normal saline or SDS solution (0.05% w/v) and stored at 5°C for 10 days. Mean histamine level in treated and control groups for the samples inoculated with either M. psychrotolerans or P. phosphoreum (≈5 log cfu/g) varied from 7 to 32 and from 49 to 66 μg/g, respectively. No synergistic effect of SDS was observed in the challenge test on meat samples. Any detectable amount of histamine was produced in the meat samples held at melting ice temperature (0–2°C) for 7 days. The effects of NTAP on the quality properties of mackerel’s filets were negligible, whereas its effect on the psychrotrophic HPB might be useful when time and environmental conditions are challenging for the cool-keeping capacity throughout the transport/storage period.

The influence of selected indigenous yeasts on Pinot Noir wine colour properties.

The use of indigenous selected starters in winemaking is gaining interest due to certain advantages for the sensory quality of the wine. The present work shows the results of a laboratory experiment in which the influence of selected indigenous yeasts on the colour characteristics of Pinot Noir was studied with the use of high hydroxycinnamate decarboxylase activity yeasts. Pichia guilliermondii ZIM624 and Wickerhamomyces anomalus S138 yeasts were used in sequential fermentation with two strains of Saccharomyces cerevisiae, the native ZIM2180 strain and commercial Fermol Premier Cru (FPC). In co-inoculation fermentations, non-Saccharomyces yeasts decreased colour intensity (on average by 25.5%). In wines fermented with ZIM624, the concentration of vinylphenolic pyranoanthocyanins increased (average concentration 1.5mg L-1 ). However, vitisin concentration was significantly higher in S138 + FPC fermentation (1.3mg L-1 and an average of 0.9mg L-1 , respectively). Pinot Noir wines fermented with only ZIM2180 and sequential inoculation of ZIM624 + ZIM2180 resulted in significantly higher colour intensity (6.1± 0.0AU and 4.4± 0.0AU, respectively) and lower wine hue parameters compared to other wines. Sensory evaluation also showed that both wines had the highest perceived colour intensity and purple colour suggesting improvement in wine quality parameters. The results confirmed that selected indigenous starters made out of Saccharomyces and non-Saccharomyces yeasts can alter Pinot Noir wine colour parameters and improve wine colour properties. Those yeasts properties should be investigated prior to the development of new commercial starters but also be considered in large scale spontaneous fermentations of low colour intensity red wines like Pinot Noir. © 2021 Society of Chemical Industry.

Effects of abscisic acid (ABA) on ethanol fermentation during postharvest ripening of Nanguo pear fruit (Pyrus ussuriensis Maxim.)

The aim of this study was to explore the role of abscisic acid (ABA) in ethanol fermentation during postharvest ripening of Nanguo pear fruit (Pyrus ussuriensis Maxim.). Pears harvest at commercial maturity were treated with 100 μmol L−1 ABA or its biosynthesis inhibitor nordihydroguaiaretic acid (NDGA). Our data indicated that ABA treatment promoted respiration rate and ethylene production during ripening compared with controls, while NDGA treatment had the opposite effects. During the early ripening stage, flesh firmness in ABA treatment group was lower than in controls; while in NDGA treatment group, it was higher than in controls. The contents of glucose, ethanol and acetaldehyde were increased by ABA treatment while reduced by NDGA treatment during ripening compared with the controls. ABA treatment promoted pyruvate and acetyl-CoA contents, whereas application of NDGA reduced pyruvate content and delayed the peak of acetyl-CoA content compared with the controls. The oxaloacetic acid (OA) and citric acid (CA) contents were reduced by ABA treatment while increased by NDGA treatment during ripening. ABA treatment promoted pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities, whereas NDGA treatment reduced their activities mainly at the early ripening stage. Quantitative real-time polymerase chain reaction (qPCR) showed that expression of PDC1, ADH1 and ADH2 was differentially up-regulated by ABA treatment during ripening while down-regulated by NDGA treatment compared with the controls. PDC2 expression was enhanced after application of NDGA during ripening while reduced by ABA treatment at the early ripening stage. Our data indicated that ABA had a promoting effect on ethanol fermentation during ripening of Nanguo pear fruit.

Exploratory Study on Histamine Content and Histidine Decarboxylase Genes of Gram-positive Bacteria in Hákarl

ABSTRACT Hákarl is a fermented fish traditionally produced in Iceland. In the present study, no scientific research has so far discussed the implication of histamine in this food. The first quantification of histamine in ready-to-eat samples of hákarl has been performed. The presence of the hdcA gene of Gram-positive bacteria, directly detected in the food matrix via qPCR, was also assessed. Histamine content was between 8.3 ± 0.8 and 13.2 ± 0.3 mg/Kg, with an overall mean of 10.6 ± 2.0 mg/Kg. Interestingly, the copy number of the hdcA gene carried by Gram-positive bacteria harbored by hákarl was below the detection limit in all the samples. Therefore, although the involvement of such a bacterial group cannot be excluded, the results suggest that the low histamine levels detected in the samples can presumably be associated with the decarboxylase activity of Gram-negative bacteria. The present study represents a step forward in understanding the microbiology of hákarl, although further investigations dealing with the monitoring of both histamine levels and microbiota dynamics during the production process are needed.

EFFECT OF WATER-SOLUBLE QUERCETIN ON INDICATORS OF OXIDATIVE-NITROSATIVE STRESS IN TISSUES OF SUBMANDIBULAR SALIVARY GLANDS OF RATS UNDER LIPOPOLYSACCHARIDE-INDUCED SYSTEMIC INFLAMMATORY RESPONSE

The aim of this study was to investigate the effect of the water-soluble form of quercetin on the indicators of oxidative-nitrosative stress in the tissues of the submandibular salivary glands (SG) under conditions of lipopolysaccharide-induced systemic inflammatory response (SIR). The study was performed on 30 white Wistar male rats weighing 180-220 g, divided into 3 groups: 1st group included intact animals, 2nd group included animals, subjected to the systemic administration of lipopolysaccharide of Salmonella typhi, 3rd group involved animals, which received water-soluble quercetin complex with polyvinylpyrrolidone (corvitin) in a dosage of 100 mg/kg (10 mg/ g in terms of quercetin) intraperitoneally every 3 days, starting on the 30 day of the experiment with using S. typhi lipopolysaccharide. The latter was administered in a dose of 0.4 μg/kg body weight 3 times during the 1st week, and then once a week for the next 7 weeks. The study has demonstrated that applying quercetin under SIR restrains the production of reactive oxygen species in SG tissues: it reduces unstimulated production of superoxide anion radical and its induced generation with the administration of NADPH (by microsomes and NO-synthase), NADH (by mitochondria), S. typhi lipopolysaccharide (by leukocyte NADPH-oxidase). The administration of quercetin under SIR condition diminishes the signs of nitrosative stress in SG tissues, as evidenced by decrease in inducible NO-synthase activity without significant changes in ornithine decarboxylase activity and the level of coupling of constitutive isoform of NO-synthase, decreased concentration of highly active peroxynitrite, but, however, without significant shift in S-nitrosothiols content.