Effect of metabolic activity of lactic acid bacteria and propionibacteria on cheese protein digestibility and fatty acid profile

This study aimed at investigating the influence of different variants of bacterial starter cultures on the metabolism of the bacteria used, cheese protein digestibility, and fatty acid profile. The results revealed that lactic acid bacteria had a significant effect on the proportions of fatty acids in cheeses, with saturated fatty acids being predominant in in all cheese variants. Fatty acid proportions are complex and depend on the type of cheese culture and monoculture used. Additionally, the analysis of fatty acid composition showed variations in the proportion of saturated and unsaturated fatty acids, impacting the values of atherogenic and thrombogenic indices. Notably, the atherogenic index was highest in samples of mature cheeses obtained from a typical mesophilic cheese culture, whereas it was lowest in samples of fresh milk and mature cheeses obtained from a mesophilic cheese culture and monocultures of Lacticaseibacillus casei and Propionibacterium. The study also highlighted the influence of lactobacilli on the content of available free lysine, glycine, and methionine in cheese proteins. Mature cheeses obtained with Propionibacterium and L. casei starter cultures exhibited higher free lysine and glycine content compared with fresh cheeses and those obtained solely with the cheese culture. Additionally, mature cheeses obtained with starter cultures of mesophilic cheese culture, Propionibacterium, and L. casei had the highest free methionine content. Based on these findings, it is evident that the choice of cheese making cultures and monocultures can significantly affect the fatty acid composition and amino acid content of cheese and fresh milk, potentially bearing important health implications.

Microbial Interactions within the Cheese Ecosystem and Their Application to Improve Quality and Safety

The cheese microbiota comprises a consortium of prokaryotic, eukaryotic and viral populations, among which lactic acid bacteria (LAB) are majority components with a prominent role during manufacturing and ripening. The assortment, numbers and proportions of LAB and other microbial biotypes making up the microbiota of cheese are affected by a range of biotic and abiotic factors. Cooperative and competitive interactions between distinct members of the microbiota may occur, with rheological, organoleptic and safety implications for ripened cheese. However, the mechanistic details of these interactions, and their functional consequences, are largely unknown. Acquiring such knowledge is important if we are to predict when fermentations will be successful and understand the causes of technological failures. The experimental use of "synthetic" microbial communities might help throw light on the dynamics of different cheese microbiota components and the interplay between them. Although synthetic communities cannot reproduce entirely the natural microbial diversity in cheese, they could help reveal basic principles governing the interactions between microbial types and perhaps allow multi-species microbial communities to be developed as functional starters. By occupying the whole ecosystem taxonomically and functionally, microbiota-based cultures might be expected to be more resilient and efficient than conventional starters in the development of unique sensorial properties.

Differential Adaptation of Propionibacterium freudenreichii CIRM-BIA129 to Cow's Milk Versus Soymilk Environments Modulates Its Stress Tolerance and Proteome

Propionibacterium freudenreichii is a beneficial bacterium that modulates the gut microbiota, motility and inflammation. It is traditionally consumed within various fermented dairy products. Changes to consumer habits in the context of food transition are, however, driving the demand for non-dairy fermented foods, resulting in a considerable development of plant-based fermented products that require greater scientific knowledge. Fermented soymilks, in particular, offer an alternative source of live probiotics. While the adaptation of lactic acid bacteria (LAB) to such vegetable substrates is well documented, little is known about that of propionibacteria. We therefore investigated the adaptation of Propionibacterium freudenreichii to soymilk by comparison to cow's milk. P. freudenreichii grew in cow's milk but not in soymilk, but it did grow in soymilk when co-cultured with the lactic acid bacterium Lactobacillus plantarum. When grown in soymilk ultrafiltrate (SUF, the aqueous phase of soymilk), P. freudenreichii cells appeared thinner and rectangular-shaped, while they were thicker and more rounded in cow's milk utltrafiltrate (MUF, the aqueous phase of cow milk). The amount of extractable surface proteins (SlpA, SlpB, SlpD, SlpE) was furthermore reduced in SUF, when compared to MUF. This included the SlpB protein, previously shown to modulate adhesion and immunomodulation in P. freudenreichii. Tolerance toward an acid and toward a bile salts challenge were enhanced in SUF. By contrast, tolerance toward an oxidative and a thermal challenge were enhanced in MUF. A whole-cell proteomic approach further identified differential expression of 35 proteins involved in amino acid transport and metabolism (including amino acid dehydrogenase, amino acid transporter), 32 proteins involved in carbohydrate transport and metabolism (including glycosyltransferase, PTS), indicating metabolic adaptation to the substrate. The culture medium also modulated the amount of stress proteins involved in stress remediation: GroEL, OpuCA, CysK, DnaJ, GrpE, in line with the modulation of stress tolerance. Changing the fermented substrate may thus significantly affect the fermentative and probiotic properties of dairy propionibacteria. This needs to be considered when developing new fermented functional foods.

Beneficial Propionibacteria within a Probiotic Emmental Cheese: Impact on Dextran Sodium Sulphate-Induced Colitis in Mice

BACKGROUNDS AND AIMS

Inflammatory Bowel Diseases (IBD), including Ulcerative Colitis (UC), coincide with alterations in the gut microbiota. Consumption of immunomodulatory strains of probiotic bacteria may induce or prolong remission in UC patients. Fermented foods, including cheeses, constitute major vectors for bacteria consumption. New evidences revealed anti-inflammatory effects in selected strains of Propionibacterium freudenreichii. We thus hypothesized that consumption of a functional cheese, fermented by such a strain, may exert a positive effect on IBD.

METHODS

We investigated the impact of cheese fermented by P. freudenreichii on gut inflammation. We developed an experimental single-strain cheese solely fermented by a selected immunomodulatory strain of P. freudenreichii, CIRM-BIA 129. We moreover produced, in industrial conditions, an Emmental cheese using the same strain, in combination with Lactobacillus delbrueckii CNRZ327 and Streptococcus thermophilus LMD-9, as starters. Consumption of both cheeses was investigated with respect to prevention of Dextran Sodium Sulphate (DSS)-induced colitis in mice.

RESULTS

Consumption of the single-strain experimental cheese, or of the industrial Emmental, both fermented by P. freudenreichii CIRM-BIA 129, reduced severity of subsequent DSS-induced colitis, weight loss, disease activity index and histological score. Both treatments, in a preventive way, reduced small bowel Immunoglobulin A (IgA) secretion, restored occludin gene expression and prevented induction of Tumor Necrosis Factor α (TNFα), Interferon γ (IFNγ) and Interleukin-17 (IL-17).

CONCLUSIONS

A combination of immunomodulatory strains of starter bacteria can be used to manufacture an anti-inflammatory cheese, as revealed in an animal model of colitis. This opens new perspectives for personalised nutrition in the context of IBD.

A bioinformatics pipeline integrating predictive metagenomics profiling for the analysis of 16S rDNA/rRNA sequencing data originated from foods

The recent advances in molecular biology, such as the advent of next-generation sequencing (NGS) platforms, have paved the way to new exciting tools which rapidly transform food microbiology. Nowadays, NGS methods such as 16S rDNA/rRNA metagenomics or amplicon sequencing are used for the taxonomic profiling of the food microbial communities. Although 16S rDNA/rRNA NGS-based microbial data are not suited for the investigation of the functional potential of the identified operational taxonomic units as compared to shotgun metagenomics, advances in the bioinformatics discipline allow now the performance of such studies. In this paper, a bioinformatics workflow is described integrating predictive metagenomics profiling with specific application to food microbiology data. Bioinformatics tools pertinent to each sub-module of the pipeline are suggested as well. The published 16S rDNA/rRNA amplicon data originated from an Italian Grana-type cheese, using an NGS platform, was employed to demonstrate the predictive metagenomics profiling approach. The pipeline identified the microbial community and the changes that occurred in the microbial profile during manufacture of the food product studied (taxonomic profiling). The workflow also indicated significant changes in the functional profiling of the community. The tool may help to investigate the functional potential, alterations, and interactions of a microbial community. The proposed workflow may also find an application in the investigation of the ecology of foodborne pathogens encountered in various food products.

Current advances in biological production of propionic acid

Propionic acid and its derivatives are considered "Generally Recognized As Safe" food additives and are generally used as an anti-microbial and anti-inflammatory agent, herbicide, and artificial flavor in diverse industrial applications. It is produced via biological pathways using Propionibacterium and some anaerobic bacteria. However, its commercial chemical synthesis from the petroleum-based feedstock is the conventional production process bit results in some environmental issues. Novel biological approaches using microorganisms and renewable biomass have attracted considerable recent attention due to economic advantages as well as great adaptation with the green technology. This review provides a comprehensive overview of important biotechnological aspects of propionic acid production using recent technologies such as employment of co-culture, genetic and metabolic engineering, immobilization technique and efficient bioreactor systems.

Microbe-microbe interactions in mixed culture food fermentations

Most known natural and industrial food fermentation processes are driven by either simple or complex communities of microorganisms. Obviously, these fermenting microbes will not only interact with the fermentable substrate but also with each other. These microbe-microbe interactions are complex but thought to be crucial for obtaining the desired product characteristics. Microbial interactions are mediated through a variety of molecular and physiological mechanisms. Examples of interaction mechanisms which have an impact on the outcome of food fermentation processes will be discussed. Finally, the technological and scientific challenges associated with the production and propagation of complex mixed starter cultures are briefly addressed. Research on the composition and functionality of complex microbial consortia is gaining momentum and will open new avenues for controlling and improving food fermentation processes, and developing new applications for mixed cultures.

Challenges in the addition of probiotic cultures to foods

Probiotic cultures are increasingly being added to foods in order to develop products with health-promoting properties. Although the literature is abundant on the beneficial effects of bifidobacteria and Lactobacillus acidophilus on health, little information is available on the challenges industry faces in adding these probiotic cultures to food products. The aim of this article is to examine seven issues that should be addressed when developing functional foods: 1) type or form of probiotic that should be used; 2) addition level required to have a beneficial effect; 3) toxicity; 4) effect of the processing steps on viability; 5) determination, in the product, of the cell populations added; 6) stability during storage; 7) changes in sensory properties of the foods.

Influence of Starter Culture Ratios and Warm Room Treatment on Free Fatty Acid and Amino Acid in Swiss Cheese

Quantification of water-soluble volatile free fatty acids (FFA) and free amino acids (FAA) was performed as a ripening index and an indirect measure of flavor development in Swiss-type cheeses. The objective of this research was to assess the effect of warm room treatment (WRT) and usage ratio of starter cultures, Streptococcus thermophilus and Lactobacillus helveticus vs. propionibacteria, on the concentration of FFA and FAA in pilot plant-scale Swiss cheese. A capillary gas chromatograph equipped with a flame ionization detector was used for the analysis of FFA in Swiss cheese. Free amino acids were analyzed by the Cd-ninhydrin method. Starter culture ratios did not affect development of FAA during the cheese ripening. However, duration of WRT had an effect on the concentration of FAA in the Swiss cheese. Free amino acids increased considerably during WRT. A continuous increase in FAA was shown during 70-d ripening time after WRT. The concentrations of C2:0 and C3:0 fatty acids were affected by starter culture ratios after 2-wk WRT, but these differences had mostly disappeared after 3-wk WRT. Similar concentrations of FFA and FAA reported in previous studies were developed in Swiss cheese with a 3-wk WRT and a 0.33:1 ratio of Streptococcus thermophilus and Lactobacillus helveticus to propionibacteria.

Effect of Lactobacillus helveticus and Propionibacterium freudenrichii ssp. shermanii combinations on propensity for split defect in Swiss cheese

One of the least controlled defects in Swiss cheese is development of splits that appear during refrigerated storage after cheese is removed from the warm room. Such fissures, or cracks, in the body of the cheese can be as short as 1 cm, or long enough to span a 90-kg block. A 2 x 2 x 2 factorial experiment was used to determine the effect of different Lactobacillus helveticus/Propionibacterium freudenreichii ssp. shermanii starter culture combinations on the occurrence of split defect in Swiss cheese. Eights vats of cheese were made in summer and eight in winter. Each 90-kg block of cheese was cut into twenty-four 4-kg blocks and graded based on the presence of splits. Only small variations were found in the composition of cheeses made during the same season. There were no correlations between moisture, pH, fat, protein, calcium, lactose contents, D/L lactate ratio, or protein degradation that could be used to predict splits after 90 d of storage. However, cheese made in the summer had 2% higher moisture content and a greater prevalence of splits. There was a sixfold increase in amount of downgraded cheese between the best and worst culture combinations used during cheese manufacture. After 90-d storage, 14 to 90% of cheese had splits in the summer, and 1 to 6% in the winter. Split formation increased with time from 60 to 120 d of storage and extent of split formation was influenced by both the lactobacilli and propionibacteria cultures used.

Peptides identified during Emmental cheese ripening: origin and proteolytic systems involved

To determine the proteolytic changes occurring during Emmental cheese ripening, peptides released in cheese aqueous phase were analyzed by reversed-phase HPLC and identified by tandem mass spectrometry sequencing, for which different strategies were illustrated by some examples. Among the 91 peptides identified, most of them arose from alpha(s1)- (51) and beta-caseins (28), and a few arose from alpha(s2)- (9) and kappa-caseins (1). An attempt was made to correlate the released peptides with the proteolytic systems potentially involved during Emmental cheese manufacture. Besides the well-known action of plasmin on beta- and alpha(s2)-caseins, and in the absence of residual fungal coagulant from Endothia parasitica, two other proteinases seem to be involved in the hydrolysis of alpha(s1)-casein in Emmental cheese: cathepsin D originated from milk and cell-envelope proteinase from thermophilic starters. Moreover, peptidases from starters were also active throughout ripening, presumably like those from nonstarter lactic acid bacteria, in contrast to those from propionic acid bacteria.