Biogenic amine production by lactic acid bacteria isolated from cider

Secondary Metabolites in Nectar-Mediated Plant-Pollinator Relationships

In recent years, our understanding of the complex chemistry of floral nectar and its ecological implications for plant-pollinator relationships has certainly increased. Nectar is no longer considered merely a reward for pollinators but rather a plant interface for complex interactions with insects and other organisms. A particular class of compounds, i.e., nectar secondary compounds (NSCs), has contributed to this new perspective, framing nectar in a more comprehensive ecological context. The aim of this review is to draft an overview of our current knowledge of NSCs, including emerging aspects such as non-protein amino acids and biogenic amines, whose presence in nectar was highlighted quite recently. After considering the implications of the different classes of NSCs in the pollination scenario, we discuss hypotheses regarding the evolution of such complex nectar profiles and provide cues for future research on plant-pollinator relationships.

Antimicrobial activity and safety features assessment of Weissella spp. from environmental sources

Weissella strains have been reported to be useful in biotechnological and probiotic determinations, and some of them are considered opportunistic pathogens. Given the widespread interest about antimicrobial susceptibilities, transmission of resistances, and virulence factors, there is little research available on such topics for Weissella. The aim of this study was to assess the safety aspects and antimicrobial potential of 54 Weissella spp. strains from different environmental sources. Antibiotic susceptibility, hemolytic activity, horizontal transfer, and antibacterial activity were studied, as well as the detection of biogenic amine BA production on decarboxylase medium and PCR was performed. All the strains were nonhemolytic and sensitive to chloramphenicol and ampicillin. Several strains were classified as resistant to fusidic acid, and very low resistance rates were detected to ciprofloxacin, tetracycline, streptomycin, lincomycin, erythromycin, and rifampicin, although all strains had intrinsic resistance to vancomycin, nalidixic acid, kanamycin, and teicoplanin. Two BA-producing strains (W. halotolerans FAS30 and FAS29) exhibited tyrosine decarboxylase activity, and just one W. confusa FS077 produced both tyramine and histamine, and their genetic determinants were identified. Ornithine decarboxylase/odc gene was found in 16 of the Weissella strains, although 3 of them synthesize putrescine. Interestingly, eight strains with good properties displayed antibacterial activity. Conjugation frequencies of erythromycin from Bacillus to Weissella spp. varied in the average of 3 × 10-9 transconjugants/recipient. However, no tetracycline-resistant transconjugant was obtained with Enterococcus faecalis JH2-2 as recipient. The obtained results support the safe status of Weissella strains, derived from environmental sources, when used as probiotics in animal feed.

Biotechnological Innovations and Therapeutic Application of Pediococcus and Lactic Acid Bacteria: The Next-Generation Microorganism

Lactic acid bacteria represent a worthwhile organism within the microbial consortium for the food sector, health, and biotechnological applications. They tend to offer high stability to environmental conditions, with an indicated increase in product yield, alongside their moderate antimicrobial activity. Lack of endotoxins and inclusion bodies, extracellular secretion, and surface display with other unique properties, are all winning attributes of these Gram-positive lactic acid bacteria, of which, Pediococcus is progressively becoming an attractive and promising host, as the next-generation probiotic comparable with other well-known model systems. Here, we presented the biotechnological developments in Pediococcal bacteriocin expression system, contemporary variegated models of Pediococcus and lactic acid bacteria strains as microbial cell factory, most recent applications as possible live delivery vector for use as therapeutics, as well as upsurging challenges and future perspective. With the radical introduction of artificial intelligence and neural network in Synthetic Biology, the microbial usage of lactic acid bacteria as an alternative eco-friendly strain, with safe use properties compared with the already known conventional strains is expected to see an increase in various food and biotechnological applications in years to come as it offers better hope of safety, accuracy, and higher efficiency.

Evaluation of Probiotic Properties and Prebiotic Utilization Potential of Weissella paramesenteroides Isolated From Fruits

Weissella paramesenteroides has gained a considerable attention as bacteriocin and exopolysaccharide producers. However, potential of W. paramesenteroides to utilize different prebiotics is unexplored area of research. Fruits being vectors of various probiotics, five W. paramesenteroides strains, namely, FX1, FX2, FX5, FX9, and FX12, were isolated from different fruits. They were screened and selected based on their ability to survive at pH 2.5 and in 1.0% sodium taurocholate, high cell surface hydrophobicity, mucin adhesion, bile-induced biofilm formation, antimicrobial activity (AMA) against selected enteropathogens, and prebiotic utilization ability, implicating the functional properties of these strains. In vitro safety evaluation showed that strains were susceptible to antibiotics except vancomycin and did not harbor any virulent traits such as biogenic amine production, hemolysis, and DNase production. Based on their functionality, two strains FX5 and FX9 were selected for prebiotic utilization studies by thin layer chromatography (TLC) and short-chain fatty acids (SCFAs) production by high performance liquid chromatography. TLC profile evinced the ability of these two strains to utilize low molecular weight galactooligosaccharides (GOS) and fructooligosaccharides (FOS), as only the upper low molecular weight fractions were disappeared from cell-free-supernatants (CFS). Enhanced β-galactosidase activity correlated with galactose accumulation in residual CFS of GOS displayed GOS utilization ability. Both the strains exhibited AMA against E. coli and Staph. aureus and high SCFAs production in the presence of prebiotic, suggesting their synbiotic potential. Thus, W. paramesenteroides strains FX5 and FX9 exhibit potential probiotic properties with prebiotic utilization and can be taken forward to evaluate synergistic synbiotic potential in detail.

Apple Fermented Products: An Overview of Technology, Properties and Health Effects

As an easily adapted culture, with overloaded production in some parts of the globe, apples and their by-products are being redirected to pharmaceutical, canning and beverages industries, both alcoholic and non-alcoholic. Fermentation is generally considered to increase the bioavailability of bioactive compounds found in apple, by impacting, through a high degree of changes, the product’s properties, including composition and health-promoting attributes, as well as their sensory profile. Probiotic apple beverages and apple vinegar are generally considered as safe and healthy products by the consumers. Recently, contributions to human health, both in vivo and in vitro studies, of non-alcoholic fermented apple-based products have been described. This review highlighted the advances in the process optimization of apple-based products considering vinegar, cider, pomace, probiotic beverages and spirits’ technologies. The different processing impacts on physical-chemical, nutritional and sensory profiles of these products are also presented. Additionally, the harmful effects of toxic compounds and strategies to limit their content in cider and apple spirits are illustrated. New trends of fermented apple-based products applicability in tangential industries are summarized.

Beer spoilage lactic acid bacteria from craft brewery microbiota: Microbiological quality and food safety

Craft beer is more susceptible to microbial spoilage because it does not have a pasteurization or filtration process, with lactic acid bacteria (LAB) being the most common beer spoilage microorganism. The aim of this study was to isolate LAB in a craft brewery and their characterization from a food safety and microbiological quality perspective, with a special focus on their abilities to produce biogenic amines (BA) and spoil the beer. The results of 60 monitored points inside the craft brewery showed that LAB associated with the craft brewing processes belonged to Lactobacillus, Pediococcus, and Leuconostoc genera, and most of them were detected in the filling area, which can lead to secondary contamination. Two isolates of L. brevis showed the most significant beer spoilage ability because they could grow in more acidic conditions, at a higher hop and alcohol content, and they displayed horA, horC, and hitA genes, which spoiled the vast majority of the tested beers. In addition, the aforementioned L. brevis isolates showed the highest BA production.

Molecular characterization of non-biogenic amines producing Lactobacillus plantarum GP11 isolated from traditional pickles using HRESI-MS analysis

Fungal spoilage and toxic biogenic amine production is a major risk in fermented products. Therefore, the selection of nontoxic biogenic amines producing probiotic bacteria plays a vital role in the fermentation process. In the present study, a total of 18 bacterial isolates were isolated from eight different homemade pickle samples and 15 lactic acid bacteria (LAB) were identified based on biochemical tests. Out of which only seven isolates (GP1, GP2, GP3, GP4, GP5, GP9, and GP11) exhibited antifungal activity against pickle contaminant Aspergillus sp and Penicillium sp. Among the potential LAB isolates, GP11 showed the highest antifungal activity against Aspergillus sp and Penicillium sp with a zone of inhibition 28.33 ± 0.57and 19.66 ± 0.57 mm respectively. The potent LAB isolates were tested for amino acid decarboxylase activity, in which GP2, GP3, GP4, and GP5 exhibited to produce tyramine, cadaverine, and phenylethylamine while GP1 and GP5 have produced tyramine and phenylethylamine respectively. However, highly potent antifungal active isolate GP11 did not produce biogenic amine. Further, GP1, GP9, and GP11 were subjected to confirmation of biogenic amines production using HRESI-MS. HRESI-MS analysis of the GP1 and GP9 sample confirmed the presence of phenylethylamine and tyramine respectively. Interestingly, GP11 isolate did not show any biogenic amines production and GP11 was further subjected to 16S rRNA typing and identified as Lactobacillus plantarum. On in situ pickle sensory evaluation, GP11 lactopickle was graded as very good quality when compared to traditional one. Therefore L. plantarum GP11 could be developed as an ideal starter culture for the fermented production of a pickle.

Impact of the Physicochemical Composition and Microbial Diversity in Apple Juice Fermentation Process: A Review

Fermented apple beverages are produced all over the world with diverse characteristics associated with each country. Despite the diversifications, cider producers are confronted with similar issues and risks. The nature of the raw material, also known as the fermentation medium, plays a key role in fermentation. A well-defined composition of apples is, therefore, required to produce cider with good quality. In addition, ferment and its metabolism are important factors in the fermentation process. The producers of cider and other alcoholic beverages are looking in general for novel yeast strains or for the use of native strains to produce "authentic" and diversified beverages that are distinct from each other, and that attract more and more consumers. Research articles on cider production are infrequent compared to wine production, especially on the impact of the chemical composition and microbial diversity of apples on fermentation. Even though the processing of fermented beverages is close in terms of microbial interactions and production, the study of the specific properties of apples and the production challenges of cider production is advantageous and meaningful for cider producers. This review summarizes the current knowledge on apple composition and the impact of the must composition on fermentation and yeast growth. In addition, the microbial diversity of cider, activities, and its influence on fermentation are reviewed.

In vitro assessment of metabolic profile of Enterococcus strains of human origin

Background

In the present study, previously isolated, safe, and avirulent enterococci strains were exploited for their metabolic profile (Bhagwat et al., Asian J Pharm Clin Res 12: 2019).

Results

Thirteen enterococci strains of human origin produced important enzymes like amylase (0.5–0.7 mg ml⁻¹), protease (192–264 mg ml⁻¹), lipase (8–10 mg ml⁻¹), bile salt hydrolase, conjugated linoleic acid (CLA), and lactic acid (highest 12 mg ml⁻¹), thus implicating potential attributes of starter cultures in food and dairy industry. Biogenic amines like arginine and tryptamine were produced after 4 days above 25 °C. Castor oil (highest yield 60 μg ml⁻¹) and sunflower oil (highest yield 48 μg ml⁻¹) both proved to be excellent sources of CLA production. Reduction assays using FRAP, ABTS (above 83%), and DPPH (30–50%) revealed excellent radical scavenging properties of cell-free supernatants of Enterococcus strains.

Conclusion

The results implicate the future potential of application enterococci for therapeutic purpose as well as the food industry.

Bacterial secretion of histamine within the gut influences immune responses within the lung

BACKGROUND

Histamine is an important immunomodulator influencing both the innate and adaptive immune system. Certain host cells express the histidine decarboxylase enzyme (HDC), which is responsible for catalysing the decarboxylation of histidine to histamine. We and others have shown that bacterial strains can also express HDC and secrete histamine; however, the influence of bacterial-derived histamine on the host immune responses distant to the gut is unclear.

METHODS

The Escherichia coli BL21 (E coli BL21) strain was genetically modified to express the Morganella morganii (M morganii)-derived HDC gene (E coli BL21_HTW). E coli BL21 and E coli BL21_HTW were gavaged to ovalbumin (OVA) sensitized and challenged mice to investigate the effect of bacterial-derived histamine on lung inflammatory responses.

RESULTS

Oral administration of E coli BL21_HTW, which is able to secrete histamine, to wild-type mice reduced lung eosinophilia and suppressed ex vivo OVA-stimulated cytokine secretion from lung cells in the OVA respiratory inflammation mouse model. In histamine receptor 2 (H2R)-deficient mice, administration of histamine-secreting bacteria also reduced inflammatory cell numbers in bronchoalveolar lavage (BAL). However, the suppressive effect of bacterial-derived histamine on BAL inflammation was lost in HDC-deficient mice. This loss of activity was associated with increased expression of histamine degrading enzymes and reduced histamine receptor expression.

CONCLUSION

Histamine secretion from bacteria within the gut can have immunological consequences at distant mucosal sites, such as within the lung. These effects are influenced by host histamine receptor expression and the expression of histamine degrading enzymes.

Biogenic Amine Production by Lactic Acid Bacteria: A Review

Lactic acid bacteria (LAB) are considered as the main biogenic amine (BA) producers in fermented foods. These compounds derive from amino acid decarboxylation through microbial activities and can cause toxic effects on humans, with symptoms (headache, heart palpitations, vomiting, diarrhea) depending also on individual sensitivity. Many studies have focused on the aminobiogenic potential of LAB associated with fermented foods, taking into consideration the conditions affecting BA accumulation and enzymes/genes involved in the biosynthetic mechanisms. This review describes in detail the different LAB (used as starter cultures to improve technological and sensorial properties, as well as those naturally occurring during ripening or in spontaneous fermentations) able to produce BAs in model or in real systems. The groups considered were enterococci, lactobacilli, streptococci, lactococci, pediococci, oenococci and, as minor producers, LAB belonging to Leuconostoc and Weissella genus. A deeper knowledge of this issue is important because decarboxylase activities are often related to strains rather than to species or genera. Moreover, this information can help to improve the selection of strains for further applications as starter or bioprotective cultures, in order to obtain high quality foods with reduced BA content.

Multiplex PCR for rapid identification of major lactic acid bacteria genera in cider and other fermented foods

Lactobacillus, Pediococcus, Oenococcus and Leuconostoc are the main Lactic Acid Bacteria (LAB) genera present in cider as they are able to survive this hostile environment. LAB play a significant role in cider quality, for example in the process of malolactic fermentation, even though they can also be involved in spoilage of cider (production of biogenic amines, exopolysaccharides, off-flavours…). In this context a better monitoring of the fermentation process is a matter of interest to guarantee cider quality. In the present study, we designed a genus-specific multiplex PCR for a rapid and simultaneous detection of the four main LAB genera involved in cider production. This multiplex PCR worked equally with purified genomic DNA of bacterial isolates and with colonies directly picked from agar plates. This new PCR method was also successfully extended to wine and dairy isolates, and thus constitutes an effective tool to quickly identify LAB associated with fermented foods. Moreover, many biodiversity studies would also benefit from this fast, cheap and reliable identification method.

Assessment of Coagulase-Negative Staphylococci and Lactic Acid Bacteria Isolated from Portuguese Dry Fermented Sausages as Potential Starters Based on Their Biogenic Amine Profile

The aim of this study was to evaluate the decarboxylase activity of coagulase-negative staphylococci (CNS) and lactic acid bacteria (LAB) involved in meat products fermentation, in order to characterize and select the strains most suitable to be used as safe starter cultures. Isolates were obtained from traditional Portuguese dry fermented meat sausages, identified by PCR and characterized according to their technological properties. Lactobacilli and enterococci were assessed for their bacteriocinogenic potential. Biogenic amines (BA) were screened by culture method and analyzed by RP-HPLC/UV. The screening method, compared with chromatographic analysis, was not reliable for CNS and LAB strains selection. Tyramine decarboxylase activity was present in CNS strains, with a slight production of amines. No other hazardous BA were produced. Among lactobacilli, moderate production of tyramine was related only to Lactobacillus curvatus, with some strains producing putrescine or 2-phenylethylamine. Enterococci were high and moderate producers of tyramine and 2-phenylethylamine, respectively. Staphylococcus xylosus, Staphylococcus equorum, and Staphylococcus carnosus, independent of their genetic and technological profiles and BA production, were adequate for use in meat products, according to the data. Lactobacillus plantarum and Lactobacillus sakei strains could also be selected for starters.

PRACTICAL APPLICATION

The selection of coagulase-negative staphylococci and lactic acid bacteria (LAB) isolates were based on their production of biogenic amines in order to avoid this potential hazard production in meat products. The most suitable isolates could be used as safe starter cultures in meat products industry. The staphylococci and LAB selected will achieve particular organoleptic characteristics in meat products and bioprotection from pathogens.

Isolation and identification of histamine-producing Enterobacteriaceae from Qu fermentation starter for Chinese rice wine brewing

Histamine (HIS) producers in fermented wines are generally believed to be lactic acid bacteria (LAB), and other microorganisms have received little or no attention. In this work, HIS-producing bacteria were isolated from Qu fermentation starter for Chinese rice wine brewing by decarboxylase medium, and their identity was confirmed by RP-HPLC and PCR. Surprisingly, the histidine decarboxylase gene (hdc) was present in only 2 out of 26 isolates. All 26 isolates were genotyped using the randomly amplified polymorphic DNA (RAPD)-PCR assay, which revealed the presence of 21 biotypes. Single type isolates were identified via 16S rRNA sequence analysis, in some cases coupled with partial sequencing of the rpoB or dnaJ gene. All isolates belonged to the Enterobacteriaceae, and included Enterobacter asburiae, Enterobacter cloacae, Enterobacter hormaechei, Citrobacter amalonaticus and Cronobacter sakazakii. All these strains were capable of producing >3.5 mg/L of HIS in TS medium without ethanol, but did not grow in TS medium with 8% ethanol. Small-scale Chinese rice wine fermentation revealed that HIS contents exhibited the same trend as the LAB and ethanol no matter what kinds of Qu were used. However, in the early stages of fermentation (from day 2 to day 4), the HIS contents had a stronger correlation with Enterobacteriaceae (0.943) than with LAB (0.369) when the Qu fermented samples are analyzed as a whole. Moreover, the lowest HIS content was measured in Xiao Qu (Q) fermented sample at the end of fermentation, which suggests that the formation of HIS in the early stages of fermentation has a decisive effect on HIS content in the final product. Our results demonstrate that Enterobacteriaceae from Qu are an important cause for HIS formation in Chinese rice wine. Consequently, selecting Qu with a low content of Enterobacteriaceae contaminants and inhibiting the growth of Enterobacteriaceae in the early stages of fermentation are useful approaches for preventing excessive amounts of HIS formation in Chinese rice wine brewing.

Accumulation of Biogenic Amines in Wine: Role of Alcoholic and Malolactic Fermentation

Biogenic amines (BAs) are detrimental to health and originate in foods mainly from decarboxylation of the corresponding amino acid by the activity of exogenous enzymes released by various microorganisms. BAs can be generated at different stages of the wine production. Some of them are formed in the vineyard and are normal constituents of grapes with amounts varying with variety, soil type and composition, fertilization and climatic conditions during growth and degree of maturation. BAs can be also formed by the yeasts during the alcoholic fermentation (AF), as well as by the action of bacteria involved in the malolactic fermentation (MLF). As aminogenesis is a complex and multifactorial phenomenon, the studies carried out to identify the main vinification stage of BAs production yielded contradictory results. In particular, there is not a general consensus yet on which fermentation supports mostly the accumulation of BAs in wine. In this context, the aim of the present paper deals with the most recent results related with the influence of alcoholic and malolactic fermentation parameters on BAs-producer microorganism in wine.

Microorganisms in Fermented Apple Beverages: Current Knowledge and Future Directions

Production of fermented apple beverages is spread all around the world with specificities in each country. 'French ciders' refer to fermented apple juice mainly produced in the northwest of France and often associated with short periods of consumption. Research articles on this kind of product are scarce compared to wine, especially on phenomena associated with microbial activities. The wine fermentation microbiome and its dynamics, organoleptic improvement for healthy and pleasant products and development of starters are now widely studied. Even if both beverages seem close in terms of microbiome and process (with both alcoholic and malolactic fermentations), the inherent properties of the raw materials and different production and environmental parameters make research on the specificities of apple fermentation beverages worthwhile. This review summarizes current knowledge on the cider microbial ecosystem, associated activities and the influence of process parameters. In addition, available data on cider quality and safety is reviewed. Finally, we focus on the future role of lactic acid bacteria and yeasts in the development of even better or new beverages made from apples.

The Impact of Carvacrol on Ammonia and Biogenic Amine Production by Common Foodborne Pathogens

The impact of carvacrol at different levels (0.1%, 0.5%, and 1%) on ammonia (AMN) and biogenic amines (BAs) production by 8 common foodborne pathogens (FBPs) (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Pseudomonas aeruginosa, Listeria monocytogenes, Aeromonas hydrophila, and Salmonella Paratyphi A) was studied using a rapid high-performance liquid chromatography method. Significant differences among bacteria (P < 0.05) in AMN and BA production were observed using a tyrosine decarboxylase broth. Tyramine, dopamine, agmatine, spermine, and putrescine were the main amines produced by the bacteria. Tyramine production by P. aeruginosa was the highest (967 mg/L), whereas K. pneumoniae was the poorest tyramine producer (6.42 mg/L). AMN and BA production varied significantly depending on carvacrol levels and the specific bacterial strains. Tyramine production for all bacterial strains was significantly suppressed by addition of carvacrol at levels of 0.5% and 1%, but not 0.1%. Consequently, the effect of carvacrol on BA and AMN formation by FBP was dependent on bacterial strain as well as carvacrol level.

Lactobacillus sicerae sp. nov., a lactic acid bacterium isolated from Spanish natural cider

Strains CUPV261T and CUPV262 were isolated from ropy natural ciders of the Basque Country, Spain, in 2007. Cells are Gram-stain positive, non-spore-forming, motile rods, facultative anaerobes and catalase-negative. The strains are obligately homofermentative (final product dl-lactate) and produce exopolysaccharides from sucrose. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the highest similarity to both isolates corresponded to the type strain of Lactobacillus vini (99.1 %), followed by Lactobacillus satsumensis (96.4 %), and Lactobacillus oeni (96.2 %), and for all other established species, 16S rRNA gene sequence similarities were below 96 %. The species delineation of strains CUPV261T and CUPV262 was evaluated through RAPD fingerprinting. In addition, a random partial genome pyrosequencing approach was performed on strain CUPV261T in order to compare it with the genome sequence of Lactobacillus vini DSM 20605T and calculate indexes of average nucleotide identity (ANI) between them. Results permit the conclusion that strains CUPV261T and CUPV262 represent a novel species of the genus Lactobacillus , for which the name Lactobacillus sicerae sp. nov. is proposed. The type strain is CUPV261T ( = CECT 8227T = KCTC 21012T).

O risco das aminas biogênicas nos alimentos

Aminas biogênicas são bases orgânicas de baixo peso molecular com atividade biológica, produzidas a partir da ação da enzima descarboxilase. Microrganismos utilizados na fermentação de alimentos são capazes de produzi-las. O consumo desses compostos causam graves efeitos toxicológicos, indesejáveis para a saúde humana. Embora não exista legislação específica sobre a quantidade máxima permitida de aminas em alimentos e bebidas, a presença e o acumulo destes compostos é de grande importância. O objetivo desta revisão é evidenciar a necessidade de mais estudos e discutir a presença de aminas biogênicas em alimentos variados.

The influences of natural zeolite (cliptinolite) on ammonia and biogenic amine formation by foodborne pathogen

The influence of natural zeolite on biogenic amines (BAs) and ammonia (AMN) production by eight common gram negative and positive foodborne pathogens (FBP) were investigated in histidine decarboxylase broth (HDB). Presence of 1% zeolite in the HDB resulted in significantly higher AMN production. Histamine (HIS) production by gram positive bacteria was as low as 0.5 mg/L, whereas Escherichia coli produced 18.96 mg/L of HIS. The use of zeolite also significantly suppressed HIS accumulation by E. coli, Pseudomonas aeruginosa, S. paratyphi A (P < 0.05), although zeolite addition stimulated HIS production by K. pneumonia and Aeromonas hydrophila. The range of tyramine (TYR) production by gram positive bacteria was 1.19 and 4.06 mg/L for Enteroccus faecalis and Listeria monocytogenes respectively. The results of study showed that the effect of zeolite on BAs and AMN production was dependent on bacterial strains, as well as zeolite concentrations used.

PRACTICAL APPLICATION

Natural zeolites are the main absorptive, low-cost material used in agriculture and industry. Although the effect of zeolite on ammonia formation in some industrial systems is well known, there is limited information regarding the impact of zeolite on biogenic amine (BA) production by foodborne pathogens. The data presented in this article will help us to understand the impact of natural zeolite on BA and ammonia production by eight common foodborne pathogens.

Does Oenococcus oeni produce histamine?

The presence of histamine in wine and other fermented foods may pose a toxicological risk for consumers. Production of histamine by Oenococcus oeni, which is the main agent of malolactic fermentation in wine and thus very important for the wine industry, has been extensively analyzed with contradictory results. If histamine production by O. oeni strains is a widespread trait, enological practices will be affected and the use of non-producing commercial O. oeni starters should be strongly recommended to avoid histamine production during winemaking. However, a review of published data showed that most evidence strongly supports the view that O. oeni is not responsible for histamine production in wine. We therefore propose the adoption of common analytical methods and the introduction of publicly-available validated histamine-producing O. oeni reference strains as a common positive control in assays to resolve this important issue.

Safety assessment of Bifidobacterium longum JDM301 based on complete genome sequences

AIM

To assess the safety of Bifidobacterium longum (B. longum) JDM301 based on complete genome sequences.

METHODS

The complete genome sequences of JDM301 were determined using the GS 20 system. Putative virulence factors, putative antibiotic resistance genes and genes encoding enzymes responsible for harmful metabolites were identified by blast with virulence factors database, antibiotic resistance genes database and genes associated with harmful metabolites in previous reports. Minimum inhibitory concentration of 16 common antimicrobial agents was evaluated by E-test.

RESULTS

JDM301 was shown to contain 36 genes associated with antibiotic resistance, 5 enzymes related to harmful metabolites and 162 nonspecific virulence factors mainly associated with transcriptional regulation, adhesion, sugar and amino acid transport. B. longum JDM301 was intrinsically resistant to ciprofloxacin, amikacin, gentamicin and streptomycin and susceptible to vancomycin, amoxicillin, cephalothin, chloramphenicol, erythromycin, ampicillin, cefotaxime, rifampicin, imipenem and trimethoprim-sulphamethoxazol. JDM301 was moderately resistant to bacitracin, while an earlier study showed that bifidobacteria were susceptible to this antibiotic. A tetracycline resistance gene with the risk of transfer was found in JDM301, which needs to be experimentally validated.

CONCLUSION

The safety assessment of JDM301 using information derived from complete bacterial genome will contribute to a wider and deeper insight into the safety of probiotic bacteria.

Characterization of the tyramine-producing pathway in Sporolactobacillus sp. P3J

A sporulated lactic acid bacterium (LAB) isolated from cider must was shown to harbour the tdc gene encoding tyrosine decarboxylase. The isolate belonged to the Sporolactobacillus genus and may correspond to a novel species. The ability of the tdc-positive strain, Sporolactobacillus sp. strain P3J, to produce tyramine in vitro was demonstrated by using HPLC. A 7535 bp nucleotide sequence harbouring the putative tdc gene was determined. Analysis of the obtained sequence showed that four tyramine production-associated genes [tyrosyl-tRNA synthetase (tyrS), tyrosine decarboxylase (tdc), tyrosine permease (tyrP) and Na(+)/H(+) antiporter (nhaC)] were present and were organized as already described in other tyramine-producing LAB. This operon was surrounded by genes showing the highest identities with mobile elements: a putative phage terminase and a putative transposase (downstream and upstream, respectively), suggesting that the tyramine-forming trait was acquired through horizontal gene transfer. Transcription analyses of the tdc gene cluster suggested that tyrS and nhaC are expressed as monocistronic genes while tdc would be part of a polycistronic mRNA together with tyrP. The presence of tyrosine in the culture medium induced the expression of all genes except for tyrS. A clear correlation was observed between initial tyrosine concentration and tyramine production combined with an increase in the final pH reached by the culture. Finally, cloning and expression of the tyrP gene in Lactococcus lactis demonstrated that its product catalyses the exchange of tyrosine and tyramine.

Occurrence of biogenic amine-forming lactic acid bacteria in wine and cider

A collection of 810 lactic acid bacteria (LAB) strains isolated from wine and cider was screened for potential biogenic amine (BA) producers by combining molecular and phenotypic approaches. A newly developed multiplex PCR method allowed for the simultaneous detection of four genes involved in the production of histamine (histidine decarboxylase, hdc), tyramine (tyrosine decarboxylase, tyrdc) and putrescine (via either ornithine decarboxylase, odc, or agmatine deiminase, agdi) while TLC and HPLC analysis allowed for BA-production determination. One hundred and fifty-eight LAB strains were monitored by the molecular/phenotypic double approach and revealed a good correlation between genotypic and phenotypic data. Eighteen per cent of the tested strains were positive for at least one BA target gene with up to three detected simultaneously, in particular amongst Lactobacillus brevis and Lactobacillus hilgardii isolates for the tyrdc and agdi genes. The most frequent gene corresponded to the agdi gene detected in 112 strains (14% of all LAB strains) of 10 different LAB species. The tyrdc gene was detected in 67 strains represented by 7 different LAB species (8% overall), especially those isolated from wine. Lower levels of hdc(+) (2% of strains) and especially odc(+) (0.5% of strains) strains were observed. Interestingly, species that have never been described to carry BA-producing pathway genes were identified in this study. Furthermore, only one cadaverine-producer was detected and corresponded to Lactobacillus 30a, a collection strain not found in fermented beverages, although cadaverine is commonly detected in wines.