Microbial quality and direct PCR identification of lactic acid bacteria and nonpathogenic Staphylococci from artisanal low-acid sausages

Detection of six species of lactic acid bacteria and six species of gram-positive catalase-positive cocci from low-acid fermented sausages (fuets and chorizos) was assessed by species-specific PCR. Without enrichment, Lactobacillus sakei and Lactobacillus curvatus were detected in 11.8% of the samples, and Lactobacillus plantarum and Staphylococcus xylosus were detected in 17.6%. Enriched samples allowed the detection of L. sakei and S. xylosus in all of the samples (100%) and of Enterococcus faecium in 11.8% of the sausages. The percentages of L. curvatus, L. plantarum, Staphylococcus carnosus, and Staphylococcus epidermidis varied depending on the sausage type. L. curvatus was detected in 80% of fuets and in 57% of chorizos. L. plantarum was found in 50% of fuets and 100% of chorizos. S. epidermidis was detected in only 11.8% of fuets, and S. carnosus was detected in only 5.9% of chorizos. Lactococcus lactis, Staphylococcus warneri, and Staphylococcus simulans were not detected in any sausage type. From a microbiological point of view, 70.6% of the samples could be considered of high quality, as they had low counts of Enterobacteriaceae and did not contain any of the food-borne pathogens assayed.     

Microbial Ecology of the Soppressata of Vallo di Diano, a Traditional Dry Fermented Sausage from Southern Italy, and In Vitro and In Situ Selection of Autochthonous Starter Cultures

The microbial ecology of “soppressata of Vallo di Diano,” a traditional dry fermented sausage from southern Italy, was studied by using both culture-dependent and culture-independent approaches. The ripened fermented sausages were characterized by high microbial loads of both staphylococci and lactobacilli. Using PCR-denaturing gradient gel electrophoresis (PCR-DGGE) targeting the variable V3 and V1 regions of the 16S rRNA gene and direct DNA sequencing, it was possible to identify Staphylococcus xylosus, S. succinus, and S. equorum among the staphylococci and Lactobacillus sakei and L. curvatus within the lactobacilli. Moreover, Debaryomyces hansenii was the main yeast species found by targeting the yeast 26S rRNA gene by PCR-DGGE. Selected strains of S. xylosus, L. sakei, and L. curvatus were characterized for their technological properties in the ripening conditions of the fermented sausages so as to select an autochthonous starter formulation. The selection included the determination of nitrate reductase, lipolytic, and antioxidant activity and proteolysis with myofibrillar and sarcoplasmic protein fractions. Such properties were evaluated in both in vitro and in situ assays; the latter were performed by using each strain as a starter in the laboratory-scale manufacture of soppressata of Vallo di Diano and by monitoring the microbiological and chemical changes at the end of ripening. The results show differences between the in vitro and in situ selection results and indicate that in situ evaluation of the technological performance of specific strains is better suited to selecting autochthonous starter cultures for fermented-meat products than in vitro evaluation.     

Study of the Ecology of Fresh Sausages and Characterization of Populations of Lactic Acid Bacteria by Molecular Methods

In this study, a polyphasic approach was used to study the ecology of fresh sausages and to characterize populations of lactic acid bacteria (LAB). The microbial profile of fresh sausages was monitored from the production day to the 10th day of storage at 4°C. Samples were collected on days 0, 3, 6, and 10, and culture-dependent and -independent methods of detection and identification were applied. Traditional plating and isolation of LAB strains, which were subsequently identified by molecular methods, and the application of PCR-denaturing gradient gel electrophoresis (DGGE) to DNA and RNA extracted directly from the fresh sausage samples allowed the study in detail of the changes in the bacterial and yeast populations during storage. Brochothrix thermosphacta and Lactobacillus sakei were the main populations present. In particular, B. thermosphacta was present throughout the process, as determined by both DNA and RNA analysis. Other bacterial species, mainly Staphylococcus xylosus, Leuconostoc mesenteroides, and L. curvatus, were detected by DGGE. Moreover, an uncultured bacterium and an uncultured Staphylococcus sp. were present, too. LAB strains isolated at day 0 were identified as Lactococcus lactis subsp. lactis, L. casei, and Enterococcus casseliflavus, and on day 3 a strain of Leuconostoc mesenteroides was identified. The remaining strains isolated belonged to L. sakei. Concerning the yeast ecology, only Debaryomyces hansenii was established in the fresh sausages. Capronia mansonii was initially present, but it was not detected after the first 3 days. At last, L. sakei isolates were characterized by randomly amplified polymorphic DNA PCR and repetitive DNA element PCR. The results obtained underlined how different populations took over at different steps of the process. This is believed to be the result of the selection of the particular population, possibly due to the low storage temperature employed.     

Characterization of the Structural Gene Encoding Nisin F, a New Lantibiotic Produced by a Lactococcus lactis subsp. lactis Isolate from Freshwater Catfish (Clarias gariepinus)

Lactococcus lactis F10, isolated from freshwater catfish, produces a bacteriocin (BacF) active against Staphylococcus aureus, Staphylococcus carnosus, Lactobacillus curvatus, Lactobacillus plantarum, and Lactobacillus reuteri. The operon encoding BacF is located on a plasmid. Sequencing of the structural gene revealed no homology to other nisin genes. Nisin F is described.     

Genetic screening of Lactobacillus sakei and Lactobacillus curvatus strains for their peptidolytic system and amino acid metabolism, and comparison of their volatilomes in a model system

A total of 51 Lactobacillus sakei and 28 Lactobacillus curvatus strains from different origins were screened for their potential to produce biogenic amines (BAs), and for their diversity of peptidolytic systems and specific aminotransferases (AraT, BcaT) that initiate amino acid conversion to volatiles relevant for aroma formation in meat products. The profiles of volatiles formed (volatilomes) were analysed in the headspace of fermentations by solid phase microextraction followed by GC-MS analysis. Tyramine-forming potential was detected only within L. curvatus and was strain-dependent. Histamine decarboxylase (HDC) activity could only be detected in one L. sakei strain, previously described as histidine decarboxylase positive (HDC⁺). Peptide transporters and peptidases were nearly ubiquitous in L. sakei and only a few strains lacked single peptidases. In L. curvatus, differences were detected in the occurrence of peptidase genes detected with PCR primers derived from L. sakei. All strains lacked known aminotransferases specific for branched-chain amino acids (BCAAs) and aromatic amino acids (ACAAs). Although L. sakei is suggested as a genetically very heterogenous species, and relatedness between L. curvatus and L. sakei at the genomic level is rather low, they appeared to be nearly uniform in the genes forming the peptidolytic system. The volatilomes of L. sakei and L. curvatus strains were qualitatively nearly identical. However, slight differences in the formation of single volatile compounds and the interaction with staphylococci may impact upon sausage fermentation which occurs over a period of many weeks. Among the compounds expected to contribute to the aroma were dimethyldisulphide, 3-methyl-1-butanol, acetic acid, 1-butanol and butanoic acid.     

Changes in the Composition of Volatile Compounds during Aging of Dry-cured Sausages

The change in the composition of volatile components during aging and storage of dry-cured sausages containing a mixture of Lactobacillus plantarumand Staphylococcus carnosusas fermenting cultures was studied by high-performance capillary gas chromatography and gas chromatography-mass spectrometry. A total of 52 compounds were identified. It was found that sausage storage is accompanied by a significant increase in the concentration of flavoring aldehydes. The terpene concentration monotonically increases with sausage aging and storage.     

Rapid Quantitative Detection of Lactobacillus sakei in Meat and Fermented Sausages by Real-Time PCR

A quick and simple method for quantitative detection of Lactobacillus sakei in fermented sausages was successfully developed. It is based on Chelex-100-based DNA purification and real-time PCR enumeration using a TaqMan fluorescence probe. Primers and probes were designed in the L. sakei 16S-23S rRNA intergenic transcribed spacer region, and the assay was evaluated using L. sakei genomic DNA and an artificially inoculated sausage model. The detection limit of this technique was approximately 3 cells per reaction mixture using both purified DNA and the inoculated sausage model. The quantification limit was established at 30 cells per reaction mixture in both models. The assay was then applied to enumerate L. sakei in real samples, and the results were compared to the MRS agar count method followed by confirmation of the percentage of L. sakei colonies. The results obtained by real-time PCR were not statistically significantly different than those obtained by plate count on MRS agar (P > 0.05), showing a satisfactory agreement between both methods. Therefore, the real-time PCR assay developed can be considered a promising rapid alternative method for the quantification of L. sakei and evaluation of the implantation of starter strains of L. sakei in fermented sausages.     

Molecular Characterization of tet(M) Genes in Lactobacillus Isolates from Different Types of Fermented Dry Sausage

The likelihood that products prepared from raw meat and milk may act as vehicles for antibiotic-resistant bacteria is currently of great concern in food safety issues. In this study, a collection of 94 tetracycline-resistant (Tc^r) lactic acid bacteria recovered from nine different fermented dry sausage types were subjected to a polyphasic molecular study with the aim of characterizing the host organisms and the tet genes, conferring tetracycline resistance, that they carry. With the (GTG)₅-PCR DNA fingerprinting technique, the Tc^r lactic acid bacterial isolates were identified as Lactobacillus plantarum, L. sakei subsp. carnosus, L. sakei subsp. sakei, L. curvatus, and L. alimentarius and typed to the intraspecies level. For a selection of 24 Tc^r lactic acid bacterial isolates displaying unique (GTG)₅-PCR fingerprints, tet genes were determined by means of PCR, and only tet(M) was detected. Restriction enzyme analysis with AccI and ScaI revealed two different tet(M) allele types. This grouping was confirmed by partial sequencing of the tet(M) open reading frame, which indicated that the two allele types displayed high sequence similarities (>99.6%) with tet(M) genes previously reported in Staphylococcus aureus MRSA 101 and in Neisseria meningitidis, respectively. Southern hybridization with plasmid profiles revealed that the isolates contained tet(M)-carrying plasmids. In addition to the tet(M) gene, one isolate also contained an erm(B) gene on a different plasmid from the one encoding the tetracycline resistance. Furthermore, it was also shown by PCR that the tet(M) genes were not located on transposons of the Tn916/Tn1545 family. To our knowledge, this is the first detailed molecular study demonstrating that taxonomically and genotypically diverse Lactobacillus strains from different types of fermented meat products can be a host for plasmid-borne tet genes.     

Culture-Dependent and -Independent Methods To Investigate the Microbial Ecology of Italian Fermented Sausages

In this study, the microbial ecology of three naturally fermented sausages produced in northeast Italy was studied by culture-dependent and -independent methods. By plating analysis, the predominance of lactic acid bacteria populations was pointed out, as well as the importance of coagulase-negative cocci. Also in the case of one fermentation, the fecal enterocci reached significant counts, highlighting their contribution to the particular transformation process. Yeast counts were higher than the detection limit (>100 CFU/g) in only one fermented sausage. Analysis of the denaturing gradient gel electrophoresis (DGGE) patterns and sequencing of the bands allowed profiling of the microbial populations present in the sausages during fermentation. The bacterial ecology was mainly characterized by the stable presence of Lactobacillus curvatus and Lactobacillus sakei, but Lactobacillus paracasei was also repeatedly detected. An important piece of evidence was the presence of Lactococcus garvieae, which clearly contributed in two fermentations. Several species of Staphylococcus were also detected. Regarding other bacterial groups, Bacillus sp., Ruminococcus sp., and Macrococcus caseolyticus were also identified at the beginning of the transformations. In addition, yeast species belonging to Debaryomyces hansenii, several Candida species, and Willopsis saturnus were observed in the DGGE gels. Finally, cluster analysis of the bacterial and yeast DGGE profiles highlighted the uniqueness of the fermentation processes studied.     

Effect of mixed starter cultures fermentation on the characteristics of silver carp sausages

To improve the quality and functionality and increase the utilization of silver carp (Hypophthalmichthys molitrix) muscle, three groups of silver carp sausages inoculated with the combinations of Staphylococcus xylosus-12 with Lactobacillus plantarum-15, Pediococcus pentosaceus-ATCC33316, and Lactobacillus casei subsp. casei-1.001, and a batch without any starter (control) were prepared. During the 48 h fermentation at 30°C, silver carp sausages inoculated with mixed starter cultures resulted in a rapid pH decrease, suppression in the growth of Enterobacteriaceae, Pseudomonas, yeasts and molds, and exhibited higher texture profiles (hardness, gumminess, springiness, and chewiness) and whiteness than the control (P < 0.05). The changes in non-protein nitrogen (NPN), free amino acid and SDS-PAGE indicated severe hydrolysis of muscle protein occurred during fermentation. Polyunsaturated fatty acids were higher in quantity in sausages with cultures compare to the control. No significant differences for taste, texture, and appearance were found among batches with mixed starters. The sausage inoculated with the combination of Lactobacillus plantarum-15, S. xylosus-12, and Lactobacillus casei subsp. casei-1.001 (S-PXC) gained highest scores for flavor and overall acceptability. There was an apparent positive correlation (r = 0.87) between the NPN and the overall acceptability in sausages, whereas pH value showed a significantly negative correlations (r = –0.89 to −0.99, P < 0.05) with taste, flavor, texture, appearance, and overall acceptability.     

Sequencing and expression analysis of sakacin genes in Lactobacillus curvatus strains

In this study, we focused our investigation on two strains of Lactobacillus curvatus, L442 and LTH1174, which are able to produce bacteriocins. L. curvatus LTH1174 is widely studied for its capability to produce curvacin A, while L. curvatus L442 was isolated from traditional Greek fermented sausages and was shown to possess a strong inhibitory activity toward Listeria monocytogenes. By polymerase chain reaction, we were able to target in both strains the genes for the production of sakacin P and sakacin Q, sppA and sppQ, respectively, both encoded chromosomally. While sppA was found to be conserved when compared with other sakacin P genes, sppQ showed a deletion of about 15 nucleotides when aligned with sequences obtained from Lactobacillus sakei. This difference did not affect the activity of sakacin Q as determined by testing sensitive strains. Expression analysis highlighted that sakacin P was expressed in L. curvatus L442 but not in L. curvatus LTH1174. Curing experiments were performed on L. curvatus LTH1174 to study the effect of the megaplasmid, present in this strain. In the plasmid-cured strain, expression of the sppA gene was detected. sppQ was expressed in both plasmid-cured and wild-type L. curvatus LTH1174, although expression was higher in the plasmid-cured strain.     

Characterization of a Theta-Type Plasmid from Lactobacillus sakei: a Potential Basis for Low-Copy-Number Vectors in Lactobacilli

The complete nucleotide sequence of the 13-kb plasmid pRV500, isolated from Lactobacillus sakei RV332, was determined. Sequence analysis enabled the identification of genes coding for a putative type I restriction-modification system, two genes coding for putative recombinases of the integrase family, and a region likely involved in replication. The structural features of this region, comprising a putative ori segment containing 11- and 22-bp repeats and a repA gene coding for a putative initiator protein, indicated that pRV500 belongs to the pUCL287 subfamily of theta-type replicons. A 3.7-kb fragment encompassing this region was fused to an Escherichia coli replicon to produce the shuttle vector pRV566 and was observed to be functional in L. sakei for plasmid replication. The L. sakei replicon alone could not support replication in E. coli. Plasmid pRV500 and its derivative pRV566 were determined to be at very low copy numbers in L. sakei. pRV566 was maintained at a reasonable rate over 20 generations in several lactobacilli, such as Lactobacillus curvatus, Lactobacillus casei, and Lactobacillus plantarum, in addition to L. sakei, making it an interesting basis for developing vectors. Sequence relationships with other plasmids are described and discussed.     

Linoleate isomerase activity occurs in lactic acid bacteria strains and is affected by pH and temperature

Aims: To investigate the ability of lactic acid bacteria (LAB) to convert linoleic acid (LA) and α‐linolenic acid (α‐LNA) to conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA), respectively. To assess pH and temperature influences on CLA and CLNA production by Lactobacillus sakei LMG 13558. Methods and Results: A screening of 48 LAB yielded one Lactobacillus curvatus, five Lactobacillus plantarum and four Lact. sakei strains displaying linoleate isomerase (LAI) activity. CLNA conversion percentages varied largely (1–60%). CLA conversion, occurring in three strains, was lower (2–5%). The LAI gene sequences of the ten LAI‐positive strains shared 75–99% identity with the LAI gene sequence of a Lact. plantarum AS1.555. At pH 6·2, CLA and CLNA production by Lact. sakei LMG 13558 was higher at 30°C than at 20 and 25°C. At pH 5·5 (30°C) or 37°C (pH 6·2), LA was not converted and α‐LNA only slightly converted. Conclusions: LAB show strain‐dependent LAI activity. Production of CLA and CLNA is affected by pH and temperature, as shown for Lact. sakei LMG 13558. Significance and Impact of the Study: Several LAB produce CLA and/or CLNA, as shown for Lact. sakei and Lact. curvatus for the first time. These findings offer potential for the manufacturing of fermented functional foods.     

Effect of hematin on the activities of nitrite reductase and catalase in lactobacilli

The effect of the addition of hematin on the activities of nitrite reductase and catalase was studied with cell suspensions of strains of lactobacillus species. In cells of Lactobacillus plantarum grown under aerobic or anaerobic conditions nitrite reductase was present. This activity was not exhibited by cells of L. curvatus and only rarely by L. sake. In addition, catalase activity was detected in aerobically grown cells only, with all strains of L. plantarum and L. sake; again L. curvatus was devoid of this activity. Ammonia was formed as the main product of nitrite reduction by L. plantarum. With lactate as the electron donor, the end products of carbohydrate catabolism were carbon dioxide, acetoin and acetate. The activities of nitrite reductase and catalase in strains of lactobacillus species may be used for optimizing the quality of starter cultures applied for the production of raw sausages.     

Multiresistance of Staphylococcus xylosus and Staphylococcus equorum from Slovak Bryndza cheese

Staphylococcus xylosus, Staphylococcus equorum, and Staphylococcus epidermidis strains were isolated from Bryndza cheese and identified using PCR method. The antimicrobial susceptibility of these strains was assessed using disc diffusion method and broth microdilution method. The highest percentage of resistance was detected for ampicillin and oxacillin, and in contrary, isolates were susceptible or intermediate resistant to ciprofloxacin and chloramphenicol. Fourteen of the S. xylosus isolates (45 %) and eleven of the S. equorum isolates (41 %) exhibited multidrug resistance. None of the S. epidermidis isolate was multiresistant. The phenotypic resistance to oxacillin was verified by PCR amplification of the gene mecA.     

Evaluation of Numerical Analysis of Random Amplified Polymorphic DNA (RAPD)-PCR as a Method to Differentiate Lactobacillus plantarum and Lactobacillus pentosus

Lactobacillus plantarum and Lactobacillus pentosus grouped into one protein profile cluster at r ≥ 0.70, separate from Lactobacillus casei, Lactobacillus sake, and Lactobacillus curvatus. Similar sugar fermentation reactions were recorded for representative strains of L. plantarum and L. pentosus. Representative strains, including the type of each species, were selected from the different protein profile clusters and their genetic relatedness determined by using numerical analysis of random amplified polymorphic DNA (RAPD)-PCR. The type strains of L. plantarum (ATCC 14917^T) and L. pentosus (NCFB 363^T) displayed different RAPD profiles and grouped into two independent clusters, well separated from L. casei, L. curvatus, and L. sake. Numerical analysis of RAPD-PCR proved a reliable and accurate method to distinguish between strains of L. plantarum and L. pentosus.     

Effects of Different Spices Used in Production of Fermented Sausages on Growth of and Curvacin A Production by Lactobacillus curvatus LTH 1174

Lactobacillus curvatus LTH 1174, a fermented sausage isolate, produces the listericidal bacteriocin curvacin A. The effect of different spices relevant for the production of fermented sausages was investigated in vitro through laboratory fermentations with a meat simulation medium and an imposed pH profile relevant for Belgian-type fermented sausages. The influence on the growth characteristics and especially on the kinetics of curvacin A production with L. curvatus LTH 1174 was evaluated. Pepper, nutmeg, rosemary, mace, and garlic all decreased the maximum specific growth rate, while paprika was the only spice that increased it. The effect on the lag phase was minor except for nutmeg and especially for garlic, which increased it, yet garlic was stimulatory for biomass production. The maximum attainable biomass concentration (X_max) was severely decreased by the addition of 0.40% (wt/vol) nutmeg, while 0.35% (wt/vol) garlic or 0.80% (wt/vol) white pepper increased X_max. Nutmeg decreased both growth and bacteriocin production considerably. Garlic was the only spice enhancing specific bacteriocin production, resulting in higher bacteriocin activity in the cell-free culture supernatant. Finally, lactic acid production was stimulated by the addition of pepper, and this was not due to the manganese present because an amount of manganese that was not growth limiting was added to the growth medium. Addition of spices to the sausage mixture is clearly a factor that will influence the effectiveness of bacteriocinogenic starter cultures in fermented-sausage manufacturing.     

Bacterial Community Structure and Location in Stilton Cheese

The microbial diversity occurring in Stilton cheese was evaluated by 16S ribosomal DNA analysis with PCR-denaturing gradient gel electrophoresis. DNA templates for PCR experiments were directly extracted from the cheese as well as bulk cells harvested from a variety of viable-count media. The variable V3 and V4-V5 regions of the 16S genes were analyzed. Closest relatives of Lactococcus lactis, Enterococcus faecalis, Lactobacillus plantarum, Lactobacillus curvatus, Leuconostoc mesenteroides, Staphylococcus equorum, and Staphylococcus sp. were identified by sequencing of the DGGE fragments. Fluorescently labeled oligonucleotide probes were developed to detect Lactococcus lactis, Lactobacillus plantarum, and Leuconostoc mesenteroides in fluorescence in situ hybridization (FISH) experiments, and their specificity for the species occurring in the community of Stilton cheese was checked in FISH experiments carried out with reference cultures. The combined use of these probes and the bacterial probe Eub338 in FISH experiments on Stilton cheese sections allowed the assessment of the spatial distribution of the different microbial species in the dairy matrix. Microbial colonies of bacteria showed a differential location in the different parts of the cheese examined: the core, the veins, and the crust. Lactococci were found in the internal part of the veins as mixed colonies and as single colonies within the core. Lactobacillus plantarum was detected only underneath the surface, while Leuconostoc microcolonies were homogeneously distributed in all parts observed. The combined molecular approach is shown to be useful to simultaneously describe the structure and location of the bacterial flora in cheese. The differential distribution of species found suggests specific ecological reasons for the establishment of sites of actual microbial growth in the cheese, with implications of significance in understanding the ecology of food systems and with the aim of achieving optimization of the fermentation technologies as well as preservation of traditional products.     

Microbial characterisation of fermented meat products from the Sicilian swine breed “Suino Nero Dei Nebrodi”

Two traditional sausage products (“salsiccia” and “salame”) processed from the raw meat of the Black Sicilian swine “Suino Nero dei Nebrodi” were microbiologically investigated during the manufacturing and ripening stages. Both products were dominated by lactic acid bacteria (LAB), especially rod-shaped types. The concentration of enterococci was consistent in salame. Coagulase-negative cocci increased slower than LAB. Yeasts showed an increasing trend during the ripening of both products. Enterobacteriaceae were counted at a constant level of about 10⁵ CFU/g in both products, while pseudomonads diminished during ripening. Coagulase-positive staphylococci, Listeria monocytogenes and Salmonella spp. were not detected at the end of the ripening process. Characterisation of LAB at the strain and species level revealed that Lactococcus lactis was found only in the meat mixture, while Lactobacillus sakei and various enterococci persisted during the monitoring period. Some LAB strains isolated from sausages were also identified on the surface of the factory equipment. Two strains (Lactobacillus sakei SS106A and Enterococcus faecalis SS91) were characterised by their anti-Listeria properties due to bacteriocin-like inhibitory substance production. A multiple strain starter composed of Lactobacillus sakei and enterococci has been proposed to maintain the typical characteristics of the two fermented meat products microbiologically investigated in this study.     

Using Surface Plasmon Resonance Technology to Screen Interactions Between Exopolysaccharides and Milk Proteins

Surface plasmon resonance-based biosensors enable the interaction between biomolecules to be monitored in real time with a label-free assay format. In the present study, the technique was used to assess the interaction between exopolysaccharides (EPS) and different milk proteins. The EPS were derived from three homopolysaccharide (HoPS)-producing Lactobacilli strains; Lactobacillus sakei, Lactobacillus plantarum, and Lactobacillus salvarius. The purified milk proteins applied were β-casein, β-lactoglobulin, and κ-casein. The results show that the binding capacity depends on the pH and decreases with increasing pH. HoPS from L. salvarius and L. sakei provided the highest binding response and interacted with κ-casein at all the tested pH values, i.e. in the range 4.0−5.5, and with β-casein at pH 4.0−5.0. When examined at pH 4.0, only HoPS from L. salvarius and L. sakei interacted with β-lactoglobulin. Under the tested conditions, HoPS from L. plantarum showed always either a lower binding response or no binding at all compared with HoPS from L. salvarius and L. sakei.