Investigating Safety and Technological Traits of a Leading Probiotic Species: Lacticaseibacillus paracasei

Lacticaseibacillus spp. are genetically close lactic acid bacteria species widely used in fermented products for their technological properties as well as their proven beneficial effects on human and animal health. This study, the first to include such a large collection of heterogeneous isolates (121) obtained from international collections belonging to Lacticaseibacillus paracasei, aimed to characterize the safety traits and technological properties of this important probiotic species, also making comparisons with other genetically related species, such as Lacticaseibacillus casei and Lacticaseibacillus zeae. These strains were isolated from a variety of heterogeneous sources, including dairy products, sourdoughs, wine, must, and human body excreta. After a preliminary molecular characterization using repetitive element palindromic PCR (Rep-PCR), Random Amplification of Polymorphic DNA (RAPD), and Sau-PCR, particular attention was paid to safety traits, evaluating antibiotic resistance profiles, biogenic amine (BA) production, the presence of genes related to the production of ethyl carbamate and diaminobenzidine (DAB), and multicopper oxidase activity (MCO). The technological characteristics of the strains, such as the capability to grow at different NaCl and ethanol concentrations and different pH values, were also investigated, as well as the production of bacteriocins. From the obtained results, it was observed that strains isolated from the same type of matrix often shared similar genetic characteristics. However, phenotypic traits were strain-specific. This underscored the vast potential of the different strains to be used for various purposes, from probiotics to bioprotective and starter cultures for food and feed production, highlighting the importance of conducting comprehensive evaluations to identify the most suitable strain for each purpose with the final aim of promoting human health.

Molecular and Physiological Properties of Indigenous Strains of Oenococcus oeni Selected from Nero di Troia Wine (Apulia, Italy)

The characterization of Oenococcus oeni strains isolated from Nero di Troia wine (Apulia, Italy) sampled in two distinct production areas was carried out. The two indigenous populations, consisting of 95 and 97 isolates, displayed high genetic diversity when analyzed by amplified fragments length polymorphisms (AFLP). Based on the UPGMA dendrogram obtained by AFLP analysis, the two populations displayed similar genotypes that grouped in the same clusters with a high level of similarity (>95%). One genotype was found in only one of the two areas. Representative strains of each cluster were analyzed for their enzymatic activities (esterase, β-glucosidase, and protease), assayed in whole cells, and tested for their metabolic properties (consumption of L-malic acid, citric acid, acetaldehyde, and arginine) and growth parameters. Significant differences among strains, including the reference strain ATCC BAA-1163, were observed for all of these properties. Principal component analysis evidenced phenotypic differences among strains, and well separated some of them belonging to different genotypes. Strains exhibiting the best performances in most of these traits could be further investigated in order to select possible candidates as malolactic starters for Nero di Troia wine. This study provided insights on the population structure of O. oeni of a local winemaking area useful to the understanding of the regional diversity of this bacterium, an issue not yet completely resolved

Biodiversity of Oenological Lactic Acid Bacteria: Species- and Strain-Dependent Plus/Minus Effects on Wine Quality and Safety

Winemaking depends on several elaborate biochemical processes that see as protagonist either yeasts or lactic acid bacteria (LAB) of oenological interest. In particular, LAB have a fundamental role in determining the quality chemical and aromatic properties of wine. They are essential not only for malic acid conversion, but also for producing several desired by-products due to their important enzymatic activities that can release volatile aromatic compounds during malolactic fermentation (e.g., esters, carbonyl compounds, thiols, monoterpenes). In addition, LAB in oenology can act as bioprotectors and reduce the content of undesired compounds. On the other hand, LAB can affect wine consumers’ health, as they can produce harmful compounds such as biogenic amines and ethyl carbamate under certain conditions during fermentation. Several of these positive and negative properties are species- and strain-dependent characteristics. This review focuses on these aspects, summarising the current state of knowledge on LAB’s oenological diversity, and highlighting their influence on the final product’s quality and safety. All our reported information is of high interest in searching new candidate strains to design starter cultures, microbial resources for traditional/typical products, and green solutions in winemaking. Due to the continuous interest in LAB as oenological bioresources, we also underline the importance of inoculation timing. The considerable variability among LAB species/strains associated with spontaneous consortia and the continuous advances in the characterisation of new species/strains of interest for applications in the wine sector suggest that the exploitation of biodiversity belonging to this heterogeneous group of bacteria is still rising.

Genomic and physiological insights into the lifestyle of Bifidobacterium species from water kefir

Water kefir is a fermented beverage employing a natural microbial consortium, which harbours bifidobacteria, namely Bifidobacterium aquikefiri and Bifidobacterium tibiigranuli. However, little information is available on their metabolic properties or role in the consortium. In this study, we combined genomic and physiologic investigations to predict and characterize the properties of these organisms and their possible role in the consortium. When comparing the genomes of these psychrotrophic organisms with that of the three selected mesophilic probiotic Bifidobacterium strains, we could find 143 genes shared by the 3 known isolates of bifidobacteria from water kefir that do not occur in the probiotic strains. These include genes involved in acid and oxygen tolerance. In addition, their genomically predicted carbohydrate usage and transport suggest adaptation to sucrose and other plant-related sugars. Furthermore, they proved prototrophic for all amino acids in vitro, which enables them to cope with the strong amino acid limitation in water kefir.

Proteomic Analysis of Lactobacillus nagelii in the Presence of Saccharomyces cerevisiae Isolated From Water Kefir and Comparison With Lactobacillus hordei

Water kefir is a slightly alcoholic and traditionally fermented beverage, which is prepared from sucrose, water, kefir grains, and dried or fresh fruits (e.g., figs). Lactobacillus (L.) nagelii, L. hordei, and Saccharomyces (S.) cerevisiae are predominant and stable lactic acid bacteria and yeasts, respectively, isolated from water kefir consortia. The growth of L. nagelii and L. hordei are improved in the presence of S. cerevisiae. In this work we demonstrate that quantitative comparative proteomics enables the investigation of interactions between LAB and yeast to predict real-time metabolic exchange in water kefir. It revealed 73 differentially expressed (DE) in L. nagelii TMW 1.1827 in the presence of S. cerevisiae. The presence of the yeast induced changes in the changes in the carbohydrate metabolism of L. nagelii and affected reactions involved in NAD⁺/NADH homeostasis. Furthermore, the DE enzymes involved in amino acid biosynthesis or catabolism predict that S. cerevisiae releases glutamine, histidine, methionine, and arginine, which are subsequently used by L. nagelii to ensure its survival in the water kefir consortium. In co-culture with S. cerevisiae, L. nagelii profits from riboflavin, most likely secreted by the yeast. The reaction of L. nagelii to the presence of S. cerevisiae differs from that one of the previously studied L. hordei, which displays 233 differentially expressed proteins, changes in citrate metabolism and an antidromic strategy for NAD⁺/NADH homeostasis. So far, aggregation promotion factors, i.e., formation of a specific glucan and bifunctional enzymes were only detected in L. hordei.

Occurrence of ethyl carbamate in three types of Chinese wines and its possible reasons

A total of 75 wines including 30 white wines, 31 red wines, and 14 sparkling wines were obtained from several regions in China (Sinkiang, Tonghua, Huailai, Yantai, Changli, Shanxi, Gansu, and Ningxia). Ethyl carbamate (EC) was detected by gas chromatography mass spectrometry. The EC concentration ranged from less than 1.16 to 38.56 μg/L, and the concentrations in 17 wines exceeded the U.S. limit for table wines (15 μg/L). The concentrations of EC increased in the order of white, red, and sparkling wines with the corresponding mean concentrations of 6.12, 9.22, and 14.03 μg/L. The relationship between EC concentration and wine type suggested that EC concentrations in wines might be affected by vinification patterns, most likely due to the difference between EC precursors in different vinification processes. This work provides a novel clue for EC contamination in different wines.

Wine composition plays an important role in the control of carcinogenic precursor formation by Lactobacillus hilgardii X₁B

BACKGROUND

Lactobacillus hilgardii, a wine lactic acid bacterium, is able to use arginine, through the arginine deiminase pathway with the formation of citrulline, a precursor of the carcinogen ethyl carbamate. The influence of different Argentine wine varieties (Merlot, Cabernet Sauvignon and Malbec), on bacterial growth and arginine metabolism was examined. Furthermore, the effect of different components normally present in wines on the enzyme activities of the arginine deiminase system was determined.

RESULTS

Malbec wine under all conditions assayed (33, 50 and 100% supplemented wine:basal media) showed higher arginine consumption and citrulline production than the other wines, as well as the highest bacterial growth and survival of Lactobacillus hilgardii X₁B. Glucose and L-malic inhibited both arginine deiminase enzymes while fructose and citric acid only inhibited arginine deiminase. The red wines assayed in this study had different composition, and this is an explanation for the different behavior of the bacterium.

CONCLUSION

The highest citrulline production in Malbec wine could be correlated with its lower concentrations of glucose, fructose, citric and phenolic acid than the other wines. Therefore, a wine with lower concentration of these sugars and acids could be dangerous due to the formation of ethyl carbamate precursors.

Effect of ethanol and low pH on citrulline and ornithine excretion and arc gene expression by strains of Lactobacillus brevis and Pediococcus pentosaceus

The accumulation of citrulline and ornithine in wine or beer as a result of the arginine catabolism of some lactic acid bacteria (LAB) species increases the risk of ethyl carbamate and putrescine formation, respectively. Several LAB species, which are found as spoilage bacteria in alcoholic beverages, have been reported to be arginine degrading. This study evaluates the effect of ethanol content and low pH on the excretion of citrulline and ornithine by two strains belonging to the potential contaminant species Lactobacillus brevis and Pediococcus pentosaceus. In the conditions that most affected cell viability, arginine consumption per cell increased noticeably, indicating that arginine utilization may be a stress responsive mechanism. L. brevis showed a higher accumulation of ornithine in the media than P. pentosaceus. In the presence of ethanol, a higher expression of the arcC gene was found in P. pentosaceus, which resulted in a lower excretion of citrulline and ornithine than in L. brevis. This suggests that L. brevis is more likely to produce these amino acids, which are precursors of ethyl carbamate and putrescine.

Metabolomics reveals alterations in both primary and secondary metabolites by wine bacteria

Lactic acid bacteria (LAB) were isolated from Korean Meoru (Vitis coigneties) wine and identified as Lactobacillus plantarum meoru0711 (KACC 91436C). The fermentative behavior and metabolic effects of L. plantarum during malolactic fermentation (MLF) were compared with those of the commercial Oenococcus oeni strain through 1H NMR- and GC-based metabolic profiling. Twenty-two primary metabolites of amino acids, carbohydrates, and organic acids, and 55 secondary metabolites of volatile compounds were identified in wines by 1H nuclear magnetic resonance (NMR) spectroscopy and gas chromatography (GC), respectively. Principal component analysis (PCA) revealed that malolactic (ML)-fermented and non-ML-fermented wines, and wines ML-fermented with O. oeni and L. plantarum were clearly differentiated. Both the primary and secondary metabolites were responsible for these differentiations. Compared to non-MLF wines, MLF wines were characterized by increased levels of primary metabolites such as lactic acid, phenylalanine, uracil, ornithine, alanine, threonine, leucine, isoleucine, and valine with decreased levels of monosaccharides, glycerol, malic, and citric acids. In addition, higher levels of secondary metabolites such as butanal, ethyl isobutylate, isobutanol, isoamyl acetate, 2-butanoate ethyl ester, isoamyl alcohol, ethyl hexanoate, glycine, acetic acid, and benzaldehyde characterized the MLF wine. Higher levels of primary metabolites such as tyrosine, monosaccharides, glycerol, alanine, 2,3-butanediol, valine, and leucine, and of secondary metabolites such as propyl acetate, isobutanol, isoamyl acetate, 1-butanol, ethyl hexanoate, prenyl alcohol, glycine, 2-hexen-1-ol, ethyl octanoate, acetic acid, benzaldehyde, and butyric, together with lower levels of lactic acid, were observed in the wines fermented by L. plantarum compared with those by O. oeni. This present study demonstrates that different genera of LAB affect both the primary and second metabolites in wine. Moreover, metabolomics with multivariate statistical analysis provide insight into wine fermentation.

Detection of arc genes related with the ethyl carbamate precursors in wine lactic acid bacteria

Trace amounts of the carcinogen ethyl carbamate can appear in wine by the reaction of ethanol with compounds such as citrulline and carbamyl phosphate, which are produced from arginine degradation by some wine lactic acid bacteria (LAB). In this work, the presence of arc genes for the arginine-deiminase pathway was studied in several strains of different species of LAB. Their ability to degrade arginine was also studied. To detect the presence of arc genes, degenerate primers were designed from the alignment of protein sequences in already sequenced LAB. The usefulness of these degenerate primers has been proven by sequencing some of the amplified PCR fragments and searching for homologies with published sequences of the same species and related ones. Correlation was found between the presence of genes and the ability to degrade arginine. Degrading strains included all heterofermentative lactobacilli, Oenococcus oeni , Pediococcus pentosaceus , and some strains of Leuconostoc mesenteroides and Lactobacillus plantarum .

Amino acids profile of sugar cane spirit (cachaça), rum, and whisky

An analytical procedure for the separation and quantification of 20 amino acids in cachaças has been developed involving C18 solid phase cleanup, derivatization with o-phthalaldehyde/2-mercaptoethanol, and reverse phase liquid chromatography with fluorescence detection. The detection limit was between 0.0050 (Cys) and 0.25 (Ser)mgL(-1), whereas the recovery index varies from 69.5 (Lys) to 100 (Tyr)%. Relative standard deviations vary from 1.39 (Trp) to 13.4 (Glu)% and from 3.08 (Glu) to 13.5 (His) for the repeatability and intermediate precision, respectively. From the quantitative profile of amino acids in 41 cachaças, 5 rums, and 12 whisky samples, the following order of amino acids in significant quantities is observed: Gly=Ser<Cys<Ile<His<Pro=Asp<Asn<Tyr for cachaça; Phe<Glu=Gln=Val=Ala<His=Gly=Thr=Arg=Tyr<Asn=Ser=Lys=Pro<Cys=Asp for rum; and Ala=Asn<Trp<Gln=His=Met=Ile=Cys<Thr<Asp=Leu<Phe=Lys<Ser=Gly=Tyr=Val<Glu=Pro<Arg for whisky samples.

Impact of winemaking practices on arginine and citrulline metabolism during and after malolactic fermentation

AIMS

To study arginine degradation and carcinogenic ethyl carbamate precursor citrulline formation during and after malolactic fermentation (MLF).

METHODS AND RESULTS

MLF was induced in white wine with two commercial Oenococcus oeni strains under different winemaking conditions regarding the type of alcoholic fermentation (spontaneous, induced) and the lees management (racked, on lees). Arginine degradation and citrulline formation did not occur during malic acid degradation in any treatment. In five of the six treatments in which arginine degradation took place, it occurred 3 weeks after malic acid depletion and significant amounts of citrulline were formed. Presence of yeast lees in wines led to increased citrulline formation.

CONCLUSIONS

This study suggests that arginine metabolism is inhibited in oenococci at low pH values (< 3.5) and that in the postalcoholic fermentation phase, citrulline formation from arginine degradation can be avoided if MLF is induced by pure cultures of O. oeni with inhibition of the bacterial biomass after malic acid depletion. Residual yeast lees in the wine have been identified as a significant risk factor for increased citrulline formation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Conclusions drawn from this study allow reducing the risk of carcinogenic ethyl carbamate formation from citrulline excretion by wine lactic acid bacteria.

Influence of ethanol and low pH on arginine and citrulline metabolism in lactic acid bacteria from wine

The aim of this work was to study the effects of ethanol on cell growth and arginine and citrulline metabolism in two heterofermentative lactic acid bacteria from wine, and to determine their possible association with the formation of ethyl carbamate (EC), a carcinogenic compound. Lactobacillus hilgardii X1B is able to utilize arginine and citrulline, while Oenococcus oeni m can only use citrulline, a precursor of EC. Growth of both microorganisms was partially inhibited by 10 and 15% (v/v) ethanol. Specific arginine consumption by L. hilgardii increased when the pH value diminished from 6.5 to 3.8, but was not affected by an increasing ethanol concentration. However, the ethanol concentration affected the specific citrulline consumption of both microorganisms. Arginine metabolism by L. hilgardii X1B increased the amount of citrulline, thus allowing production of EC in the medium. Citrulline utilization by both microorganisms, at all pH values studied, indirectly inhibited the formation of EC; indeed, one of the precursors had practically disappeared after 48 h of incubation. Due to its ability to form precursors, L. hilgardii X1B has the potential to contribute to EC formation, whereas citrulline utilization by O. oeni m in the presence of ethanol may contribute to diminishing the formation of EC. Rapid degradation of citrulline in the presence of ethanol by O. oeni m is important from a toxicological point of view, because it is important to keep the EC levels as low as possible.

Wine volatile and amino acid composition after malolactic fermentation: effect of Oenococcus oeni and Lactobacillus plantarum starter cultures

Red wine amino acids and volatile compounds were analyzed before and after malolactic fermentation carried out by four different starter cultures of the species Oenococcus oeni and Lactobacillus plantarum. The purpose of this study was to determine whether differences can be attributed to the lactic acid bacteria strain used in this important step of the wine-making process. The malolactic cultures selected for this study were indigenous wine lactic acid bacteria strains. The data were evaluated using different multivariate analysis techniques. Results showed different malolactic behaviors for O. oeni and L. plantarum and significant metabolic differences between both species. A degree of diversity was found within each lactic acid bacteria group, since wines presented specific characteristics depending on the lactic acid bacteria strain used. In all cases, malolactic fermentation seemed to modify the amino acid and volatile composition of the wine.

Molecular characterization of Oenococcus oeni genes encoding proteins involved in arginine transport

AIMS

This work was carried out to complete the sequence of the arc cluster involved in arginine catabolism in Oenococcus oeni, and particularly to characterize the genes encoding proteins involved in arginine transport.

METHODS AND RESULTS

Using molecular cloning, two loci encoding proteins involved in the arginine-ornithine antiport were isolated. Their expression patterns were monitored by RT-PCR to study the influence of arginine on their transcription. Polycistronic mRNAs were detected. PCR performed directly on colonies with primer pairs specific of arc genes was used to discriminate strains able/unable to degrade arginine.

CONCLUSIONS

Oenococcus oeni contains two arcD loci encoding similar proteins. Their expression is not influenced by arginine and polycistronic messengers were detected. The inability to use arginine is due to a lack of genetic information encoding proteins of the arginine deiminase pathway.

SIGNIFICANCE AND IMPACT OF THE STUDY

The constitutive expression of arcD genes points to the positive role of arginine on O. oeni cell growth. The occasional presence of all the arc ABCD genes together in O. oeni strains might provide insights into the growth rate variability within this species.