Evaluation of lactic acid bacteria strains isolated from fructose-rich environments for their mannitol-production and milk-gelation abilities

Synergistic effect of the coculture of Leuconostoc pseudomesenteroides and Lactococcus lactis, isolated from honeybees, on the generation of plant-based dairy alternatives based on soy, pea, oat, and potato drinks

The production of plant-based dairy alternatives has been majorly focused on the improvement of sensorial, technological and nutritional properties, to be able to mimic and replace milk-based fermented products. The presence of off-flavours and antinutrients, the lack of production of dairy-like flavours or the metabolic inaccessibility of plant proteins are some of the challenges to overcome to generate plant-based dairy alternatives. However, in the present study, it is demonstrated how the synergistic effect of two LAB strains, when cocultured, can simultaneously solve those challenges when fermenting in four different plant-based raw materials: soy, pea, oat, and potato drinks (SPOP). The fermentation was performed through the mono- and co-culture of the two LAB strains isolated from Apis mellifera (honeybee): Leuconostoc pseudomesenteroides NFICC 2004 and Lactococcus lactis NFICC 2005. Firstly, the coculture of both strains demonstrated to increase the acidification rate of the four plant matrices. Moreover, L. pseudomesenteroides (LP) demonstrated to in situ produce high concentrations of mannitol when fructose was present as C-source. Furthermore, L. pseudomesenteroides, which encoded for PII-proteinase, demonstrated to break down SPOP proteins, releasing free amino acids that were used by L.lactis (LL) for growth and metabolism. Lastly, the analysis of their co-metabolic volatile performance showed the principal ability of removal of the main off-flavours found in SPOP, such as hexanal, 1-octen-3-ol, 2-pentylfuran, pentanal, octanal, heptanal, and nonanal, mainly led by L. pseudomesenteroides, as well as the production of dairy-like flavours, such as diacetyl and 3-methyl-1-butanol, triggered by L. lactis metabolism. Overall, these findings endorsed the use of honeybee isolated strains as starter cultures, demonstrated the potential of coupling genotypes and phenotypes of multiple strains to improve the organoleptic properties suggesting a potential of combining plant-based matrices for the generation of future high-quality plant-based dairy alternatives.

Selecting autochthonous lactic acid bacteria for co-inoculation in Chinese bayberry wine production: Stress response, starter cultures application and volatilomic study

This study focused on isolating and characterising autochthonous lactic acid bacteria (LAB) from spontaneously fermented Chinese bayberry (CB) and their potential application in CB wine fermentation in co-inoculation with yeast starter cultures. Numerous LAB, including Lactiplantibacillus (Lp.) plantarum (9), Limosilactobacillus (Lb.) fermentum (6), Lactococcus (Lc.) lactis (3), Enterococcus (Ec.) hirae (1), Leuconostoc (Le.) mesenteroides (1), and Weissella (Ws.) cibaria (1), were isolated and identified. The isolated strains Lp. plantarum ZFM710 and ZFM715, together with Lb. fermentum ZFM720 and ZFM722, adapted well to unfavourable fermentation environment, including ethanol, osmolality, and acidity stresses, were selected for producing CB wine by co-inoculation with Saccharomyces cerevisiae. During fermentation, the presence of LAB promoted the development of S. cerevisiae, while the population dynamics of LAB in different groups at different stages showed strain-specific differences. Fermentation trials involving LAB yielded a lower ethanol concentration except for Lp. plantarum ZFM715. Compared to the pure S. cerevisiae fermented sample, the addition of LAB led to a clear modulation in organic acid composition. Lb. fermentum strains in co-fermentation led to significant decreases in each classified group of aroma compounds, while Lp. plantarum ZFM715 significantly increased the complexity and intensity of aroma compounds, as well as the intensities of fruity and floral notes. The study selects interesting strains for the design of starter cultures for use in CB wine production, underlining the interest in the selection of autochthonous LAB in fruit wines, with the aim of improving the adaptation of bacteria to specific environmental conditions and shaping the unique traits of the finished products.

Recent trends in lactic acid-producing microorganisms through microbial fermentation for the synthesis of polylactic acid

Polylactic acid (PLA) is a range of unique bioplastics that are bio-based and biodegradable. PLA is currently driving market expansion for lactic acid (LA) due to its high demand as a building block in production. One of the most practical and environmentally benign techniques for synthesising PLA is through enzymatic polymerisation of microbial LA monomers. However, microbial LA fermentation does have some limitations. Firstly, it requires the use of a nutritionally rich medium. Secondly, LA production can be disrupted by bacteriophage infection or other microorganisms. Lastly, the yield can be low due to the formation of by-products through heterofermentative pathway. Considering the potential use of PLA as a replacement for conventional petrochemical-based polymers in industrial applications, researchers are focused on exploring the diversity of LA-producing microorganisms from various niches. Their goal is to study the functional properties of these microorganisms and their ability to produce industrially valuable metabolites. This review highlights the advantages and disadvantages of lactic acid-producing microorganisms used in microbial fermentation for PLA synthesis.

Food gels: principles, interaction mechanisms and its microstructure

Food hydrogels are important materials having great scientific interest due to biocompatibility, safety and environment-friendly characteristics. In the food industry, hydrogels are widely used due to their three-dimensional crosslinked networks. Furthermore, they have attracted great attention due to their wide range of applications in the food industry, such as fat replacers, encapsulating agents, target delivery vehicles, and many more. In addition to basic and recent knowledge on food hydrogels, this review exclusively focuses on sensorial perceptions, nutritional significance, body interactions, network structures, mechanical properties, and potential hydrogel applications in food and food-based matrices. Additionally, this review highlights the structural design of hydrogels, which provide the forward-looking idea for future applications of food hydrogels (e.g., 3D or 4D printing).

Genomic diversity in Fructobacillus spp. isolated from fructose-rich niches

The Fructobacillus genus is a group of obligately fructophilic lactic acid bacteria (FLAB) that requires the use of fructose or another electron acceptor for their growth. In this work, we performed a comparative genomic analysis within the genus Fructobacillus by using 24 available genomes to evaluate genomic and metabolic differences among these organisms. In the genome of these strains, which varies between 1.15- and 1.75-Mbp, nineteen intact prophage regions, and seven complete CRISPR-Cas type II systems were found. Phylogenetic analyses located the studied genomes in two different clades. A pangenome analysis and a functional classification of their genes revealed that genomes of the first clade presented fewer genes involved in the synthesis of amino acids and other nitrogen compounds. Moreover, the presence of genes strictly related to the use of fructose and electron acceptors was variable within the genus, although these variations were not always related to the phylogeny.

Fructose-induced topographical changes in fructophilic, pseudofructophilic and non-fructophilic lactic acid bacterial strains with genomic comparison

Fructophilic Lactic Acid Bacteria (FLAB), Fructobacillus fructosus DPC7238 and pseudofructophilic Leuconostoc mesenteroides DPC7261 and non-FLAB Limosilactobacillus reuteri DSM20016 strains were studied for their growth and morphological evolution as a function of increased fructose concentrations (0, 25, and 50% w/v) in the media. A comparison of the genomics of these strains was carried out to relate observed changes and understand fructose-rich adaptations. The viability of FLAB strains were reduced by approx. 50% at a 50% fructose concentration, while the Limosilactobacillus reuteri strain was reduced to approx. 98%. Electron microscopy demonstrated that FLAB strain, Fructobacillus. fructosus and pseudofructophilic Leuc. mesenteroides, were intact but expanded in the presence of high fructose in the medium. Limosilactobacillus reuteri, on the other hand, ruptured as a result of excessive elongation, resulting in the formation of cell debris when the medium contained more than 25% (w/v) fructose. This was entirely and quantitatively corroborated by three-dimensional data obtained by scanning several single cells using an atomic force microscope. The damage caused the bacterial envelope to elongate lengthwise, thus increasing width size and lower height. The cell surface became comparatively smoother at 25% fructose while rougher at 50% fructose, irrespective of the strains. Although Fructobacillus fructosus was highly fructose tolerant and maintained topological integrity, it had a comparatively smaller genome than pseudofructophilic Leuc. mesenteroides. Further, COG analysis identified lower but effective numbers of genes in fructose metabolism and transport of Fructobacillus fructosus, essentially needed for adaptability in fructose-rich niches.

In vivo monitoring of Lactiplantibacillus plantarum in the nasal and vaginal mucosa using infrared fluorescence

Lactic acid bacteria (LAB) of the genus Lactiplantibacillus have been explored as potential mucosal vaccine vectors due to their ability to elicit an immune response against expressed foreign antigens and to their safety. However, tools for monitoring LAB distribution and persistence at the mucosal surfaces are needed. Here, we characterize Lactiplantibacillus plantarum bacteria expressing the infrared fluorescent protein IRFP713 for exploring their in vivo distribution in the mucosa and potential use as a mucosal vaccine vector. This bacterial species is commonly used as a vaginal probiotic and was recently found to have a niche in the human nose. Three different fluorescent L. plantarum strains were obtained using the nisin-inducible pNZRK-IRFP713 plasmid which contains the nisRK genes, showing stable and constitutive expression of IRFP713 in vitro. One of these strains was further monitored in BALB/c mice using near-infrared fluorescence, indicating successful colonization of the nasal and vaginal mucosae for up to 72 h. This study thus provides a tool for the in vivo spatiotemporal monitoring of lactiplantibacilli, allowing non-invasive bacterial detection in these mucosal sites. KEY POINTS: • Stable and constitutive expression of the IRFP713 protein was obtained in different L. plantarum strains. • IRFP713⁺ L. plantarum 3.12.1 was monitored in vivo using near-infrared fluorescence. • Residence times observed after intranasal and vaginal inoculation were 24-72 h.

Mannitol Production by Heterofermentative Lactic Acid Bacteria: a Review

Obesity, diabetes, and other cardiovascular diseases are directly related to the high consumption of processed sugars with high caloric content. The current food industry has novel trends related to replacing highly caloric sugars with non-caloric or low-calorie sweeteners. Mannitol, a polyol, represents a suitable substitute because it has a low caloric content and does not induce a glycemic response, which is crucial for diabetic people. Consequently, this polyol has multiple applications in the food, pharmaceutical, and medicine industries. Mannitol can be produced by plant extraction, chemical or enzymatic synthesis, or microbial fermentation. Different in vitro processes have been developed regarding enzymatic synthesis to obtain mannitol from fructose, glucose, or starch-derived substrates. Various microorganisms such as yeast, fungi, and bacteria are applied for microbial fermentation. Among them, heterofermentative lactic acid bacteria (LAB) represent a reliable and feasible alternative due to their metabolic characteristics. In this regard, the yield and productivity of mannitol depend on the culture system, the growing conditions, and the culture medium composition. In situ mannitol production represents a novel approach to decrease the sugar content in food and beverages. Also, genetic engineering offers an interesting option to obtain mannitol-producing strains. This review presents and discusses the most significant advances that have been made in the mannitol production through fermentation by heterofermentative LAB, including the pertinent and critical analysis of culture conditions considering broth composition, reaction systems, and their effects on productivities and yields.

Draft Genome Sequences of Fructobacillus fructosus DPC 7238 and Leuconostoc mesenteroides DPC 7261, Mannitol-Producing Organisms Isolated from Fructose-Rich Honeybee-Resident Flowers on an Irish Farm

Certain bacterial species, including some fructophilic lactic acid bacteria, are known to naturally produce the sugar alcohol mannitol. Here, we announce the draft genome sequences of the mannitol-producing organisms Fructobacillus fructosus DPC 7238 and Leuconostoc mesenteroides DPC 7261, which were isolated from fructose-rich honeybee-resident flowers found on an Irish farm.

Certain bacterial species, including some fructophilic lactic acid bacteria, are known to naturally produce the sugar alcohol mannitol. Here, we announce the draft genome sequences of the mannitol-producing organisms Fructobacillus fructosus DPC 7238 and Leuconostoc mesenteroides DPC 7261, which were isolated from fructose-rich honeybee-resident flowers found on an Irish farm.