Labeling quality and molecular characterization studies of products containing Lactobacillus spp. strains

Recent and Advanced DNA-Based Technologies for the Authentication of Probiotic, Protected Designation of Origin (PDO) and Protected Geographical Indication (PGI) Fermented Foods and Beverages

The authenticity of probiotic products and fermented foods and beverages that have the status of protected designation of origin (PDO) or geographical indication (PGI) can be assessed via numerous methods. DNA-based technologies have emerged in recent decades as valuable tools to achieve food authentication, and advanced DNA-based methods and platforms are being developed. The present review focuses on the recent and advanced DNA-based techniques for the authentication of probiotic, PDO and PGI fermented foods and beverages. Moreover, the most promising DNA-based detection tools are presented. Strain- and species-specific DNA-based markers of microorganisms used as starter cultures or (probiotic) adjuncts for the production of probiotic and fermented food and beverages have been exploited for valuable authentication in several detection methods. Among the available technologies, propidium monoazide (PMA) real-time polymerase chain reaction (PCR)-based technologies allow for the on-time quantitative detection of viable microbes. DNA-based lab-on-a-chips are promising devices that can be used for the on-site and on-time quantitative detection of microorganisms. PCR-DGGE and metagenomics, even combined with the use of PMA, are valuable tools allowing for the fingerprinting of the microbial communities, which characterize PDO and PGI fermented foods and beverages, and they are necessary for authentication besides permitting the detection of extra or mislabeled species in probiotic products. These methods, in relation to the authentication of probiotic foods and beverages, need to be used in combination with PMA, culturomics or flow cytometry to allow for the enumeration of viable microorganisms.

Characterization of Bifidobacterium asteroides Isolates

Bifidobacteria have long been recognized as bacteria with probiotic and therapeutic features. The aim of this work is to characterize the Bifidobacterium asteroides BA15 and BA17 strains, isolated from honeybee gut, to evaluate its safety for human use. An in-depth assessment was carried out on safety properties (antibiotic resistance profiling, β-hemolytic, DNase and gelatinase activities and virulence factor presence) and other properties (antimicrobial activity, auto-aggregation, co-aggregation and hydrophobicity). Based on phenotypic and genotypic characterization, both strains satisfied all the safety requirements. More specifically, genome analysis showed the absence of genes encoding for glycopeptide (vanA, vanB, vanC-1, vanC-2, vanD, vanE, vanG), resistance to tetracycline (tetM, tetL and tetO) and virulence genes (asa1, gelE, cylA, esp, hyl).

Spotlight on the Compositional Quality of Probiotic Formulations Marketed Worldwide

On the worldwide market, a great number of probiotic formulations are available to consumers as drugs, dietary supplements, and functional foods. For exerting their beneficial effects on host health, these preparations should contain a sufficient amount of the indicated living microbes and be pathogen-free to be safe. Therefore, the contained microbial species and their amount until product expiry are required to be accurately reported on the labels. While commercial formulations licensed as drugs are subjected to rigorous quality controls, less stringent regulations are generally applied to preparations categorized as dietary supplements and functional foods. Many reports indicated that the content of several probiotic formulations does not always correspond to the label claims in terms of microbial identification, number of living organisms, and purity, highlighting the requirement for more stringent quality controls by manufacturers. The main focus of this review is to provide an in-depth overview of the microbiological quality of probiotic formulations commercialized worldwide. Many incongruences in the compositional quality of some probiotic formulations available on the worldwide market were highlighted. Even if manufacturers carry at least some of the responsibility for these inconsistencies, studies that analyze probiotic products should be conducted following recommended and up-to-date methodologies.

Evaluation of Dietary Supplements Containing Viable Bacteria by Cultivation/MALDI-TOF Mass Spectrometry and PCR Identification

The insufficient quality of products containing beneficial live bacteria in terms of content and viability of labelled microorganisms is an often-reported problem. The aim of this work was to evaluate the quality of dietary supplements containing viable bacteria available in Slovenian pharmacies using plate counting, matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and species- or subspecies-specific PCR with DNA isolated from consortia of viable bacteria, from individual isolates, or directly from the products. Twelve percent of the products (3 of 26) contained insufficient numbers of viable bacteria. Eighty-three of the labelled species (111 in total) were confirmed by PCR with DNA from the product; 74% of these were confirmed by PCR with DNA from viable consortium, and 65% of these were confirmed by MALDI-TOF MS analysis of colonies. Certain species in multi-strain products were confirmed by PCR with DNA from viable consortia but not by MALDI-TOF MS, suggesting that the number of isolates examined (three per labelled strain) was too low. With the exception of Lacticaseibacillus casei and closely related species (Lacticaseibacillus rhamnosus and Lacticaseibacillus zeae), PCR and MALDI-TOF identification results agreed for 99% of the isolates examined, although several MALDI-TOF results had lower score values (1.700-1.999), indicating that the species identification was not reliable. The species L. zeae, which appeared in 20 matches of the Biotyper analysis, was identified as L. rhamnosus by PCR. The MALDI-TOF MS analysis was also unsuccessful in detecting Lactobacillus acidophilus La-5 and Bacillus coagulans due to missing peaks and unreliable identification, respectively. Mislabelling was detected by both methods for two putative L. casei strains that turned out to belong to the species Lacticaseibacillus paracasei. PCR remains more successful in subspecies-level identification as long as the database of MALDI-TOF MS spectra is not expanded by building in-house databases. The lack of positive PCR results with viable consortia or colonies, but positive PCR results with DNA isolated directly from the products observed in 10% (11/112) of the labelled strains, suggests the presence of non-culturable bacteria in the products. MALDI-TOF MS is a faster and simpler alternative to PCR identification, provided that a sufficient number of colonies are examined. Generation of in-house library may further improve the identification accuracy at the species and sub-species level.

Authenticity of probiotic foods and dietary supplements: A pivotal issue to address

The market of probiotic foods and supplements is growing rapidly but frequently the commercialized products are not compliant with their labels in terms of claimed probiotic strain(s) and labeled number of viable probiotic cells, thus mining the authenticity of these probiotic products.In this review, we provide an up-to-date overview of: (i) the current regulatory aspects, (ii) the consistency of probiotic foods and supplements with their labels, (iii) the implications of mislabeling on the quality, safety and functionality of these products and (iv) the available and most promising methods to assess the authenticity of these products, taking into account the need to discriminate among the different physiological states probiotics might be in the carrier matrices. It arises that authenticity of probiotic foods and supplements is an urgent issue, of industrial and legislation relevance, that need to be addressed. A plethora of methods are available to reach this goal, each with its own advantages and disadvantages. Protocols that combine the use of propidium monoazide (PMA) with metagenomics or polyphasic approaches including the PMA real time PCR or flow cytometry (for the viability assessment) and the whole genome sequence analysis (for the identification and typing of the probiotic strain) are the most promising that should be standardized and used by producers and regulators.

In vitro inhibitory activity of Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 alone or in combination against bacterial and Candida reference strains and clinical isolates

Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 are two strains frequently used as probiotic components in food supplements. The decrease of potentially pathogenic gastrointestinal microorganisms is one of their claimed mechanisms. The aim of this study was to investigate their ability, alone or in combination, to inhibit in vitro the growth of Gram-negative, Gram-positive and Candida reference strains and clinical isolates, using different methods. The cell-free supernatants were obtained by centrifugation and filtration from single or mixed broth cultures and the inhibitory activity was tested using both agar-well diffusion and broth microdilution methods. In order to get some preliminary information about the chemical nature of the active metabolites released in the supernatants, the inhibitory activity was investigated after neutralization, heat and proteolytic treatments. The highest inhibitory activity was shown by the untreated supernatant obtained from broth culture of the two probiotic strains, especially against bacterial reference strains and clinical isolates. This supernatant showed inhibitory activity towards Candida species, too. A decreased inhibitory activity was observed for the supernatants obtained from single cultures and after proteolytic treatment, against bacterial reference strains. The study suggests that the combination of B. longum BB536 and L. rhamnosus HN001 could represent a possible alternative against gastrointestinal and urinary pathogens either as prophylaxis or as treatment.

Status of microbial based cleaning products in statutory regulations and ecolabelling in Europe, the USA, and Canada

Cleaning products containing living microorganisms as active ingredients are increasingly being used in household, professional and industrial cleaning applications. Microorganisms can degrade soiling associated with dirt, food residues, and grease by enzymatic and metabolic action and out-compete microorganisms associated with odor problems. Their potential for odor control seems to result in a competitive advantage over conventional chemically-based cleaning products. Moreover, producers of microbial-based cleaning products (MBCPs) claim that their products are less harmful to the environment. These promising prospects have triggered interest from consumer and environmental organizations, professional users, and regulators in understanding if there are also possible negative health and environmental impacts which require attention and how the safety of these products is ensured. Unfortunately, there is little information on these issues in the public domain. Moreover, regulatory oversight in Europe is essentially limited to pathogenic properties in the context of worker protection. Canada, in contrast, has a regulatory framework in place to assess risks to human health and the environment from the manufacture, import and/or use of new microorganisms contained in MBCPs. In the absence of mandatory standards, safety assessment and hygienic practices seem to vary considerably across companies. Recently developed ecolabelling standards are - for the time being - the only option for transparent compliance to minimum standards in terms of safety as well as assessments of manufacturer information by third parties. These standards highlight in particular the need for precise taxonomic information for assessing the pathogenic properties and the need to ensure the absence of potentially harmful microorganisms as contaminants. Ecolabelling standards are, however, voluntary and do not cover all relevant safety issues. In order to develop a more comprehensive set of mandatory standards for health and safety, a number of areas would benefit from further research (e.g. the role in plant pathogenicity and other environmental properties of the microorganisms used; the relevance of chronic exposure to dusts and aerosols containing vegetative cells and spores; the relevance of strains which belong to species known to include opportunistic pathogens and possible hazards for particularly sensitive risk groups). Improved knowledge in these areas will contribute to a predictable level of product safety.