Genetic mechanisms of prebiotic carbohydrate metabolism in lactic acid bacteria: Emphasis on Lacticaseibacillus casei and Lacticaseibacillus paracasei as flexible, diverse and outstanding prebiotic carbohydrate starters

Mechanistic evaluation of enhanced graphene toxicity to Bacillus induced by humic acid adsorption

The extensive application of graphene nanosheets (GNSs) has raised concerns over risks to sensitive species in the aquatic environment. The humic acid (HA) corona is traditionally considered to reduce GNSs toxicity. Here, we evaluate the effect of sorbed HA (GNSs-HA) on the toxicity of GNSs to Gram positive Bacillus tropicus. Contrary to previous data, GNSs-HA exhibits greater toxicity compared to GNSs. Multi-omics combined with sensitive bioassays and electrochemical methods reveals GNSs disrupt oxidative phosphorylation by causing physical membrane damage. This leads to the accumulation of intracellular reactive oxygen species and inhibition of ATP production, subsequently suppressing synthetic and metabolic processes and ultimately causing bacterial death. Conversely, GNSs-HA directly extracts electrons from bacteria and oxidized biomolecules due to HA-improved electron transfer. This finding suggests that the HA corona does not always mitigate the toxicity of nanoparticles, thereby introducing uncertainty over the interaction between environmental corona and nanoparticles during ecological risk evaluation.

Antineoplastic with DNA fragmentation assay and anti-oxidant, anti-inflammatory with gene expression activity of Lactobacillus plantarum isolated from local Egyptian milk products

Many lactic acid bacteria (LAB), known for their human health benefits, are derived from milk and utilized in biotherapeutic applications or for producing valuable nutraceuticals. However, the specific role of milk-associated LAB in biotherapeutics remains underexplored. To address this, eight milk product samples were randomly selected from the Egyptian market, diluted, and then cultured anaerobically on MRS agar. Subsequently, 16 suspected LAB isolates were recovered and underwent rapid preliminary identification. Among these isolates, the Lactobacillus plantarum strain with accession number (OQ547261.1) was identified due to its strong antioxidant activity depending on the DPPH assay, L. plantarum displayed notable antioxidant activities of 71.8% and 93.8% at concentrations of 125-1000 µg/mL, respectively. While ascorbic acid showed lower concentrations of 7.81, 3.9, and 1.95 µg/mL which showed activities of 45.1%, 34.2%, and 27.2%, respectively. The anti-inflammatory efficacy of L. plantarum was evaluated based on its capability to prevent hemolysis induced by hypotonic conditions. At a concentration of 1000 µg/mL, L. plantarum could reduce hemolysis by 97.7%, nearly matching the 99.5% inhibition rate achieved by the standard drug, indomethacin, at an identical concentration. Moreover, L. plantarum exhibited high hemolytic activity at 100 µg/mL (14.3%), which decreased to 1.4% at 1000 µg/mL. The abundance of phenolic acids and flavonoids was determined by high-performance liquid chromatography (HPLC) in L. plantarum. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) demonstrated that L. plantarum increased gene expression of the inflammatory marker TLR2 by 133%, and cellular oxidation markers SOD1 and SOD2 by 65% and 74.2%, respectively, while suppressing CRP expression by 33.3%. These results underscore L. plantarum's exceptional anti-inflammatory and antioxidant activities. Furthermore, L. plantarum induces cancer cell death through necrotic nuclear DNA fragmentation. These findings suggest that L. plantarum is not only suitable for nutraceutical production but also holds potential as a probiotic strain. Future research should focus on enhancing the capacity of this strain across various industries and fostering innovation in multiple fields.

Lactic acid production by Lactobacillus casei using a sequence of seasonally available fruit wastes as sustainable carbon sources

Introduction: Lactic acid (LA) production from fossil resources is unsustainable owing to their depletion and environmental concerns. Thus, this study aimed to optimize the production of LA by Lactobacillus casei in a cultured medium containing fruit wastes (FWs) from agro-industries and second cheese whey (SCW) from dairy production, supplemented with maize steep liquor (MSL, 10% v/v) as the nitrogen source. Methods: The FWs were selected based on seasonal availability [early summer (early ripening peach), full summer (melon), late summer (pear), and early autumn (apple)] and SCW as annual waste. Small-scale preliminary tests as well as controlled fermenter experiments were performed to demonstrate the potential of using various food wastes as substrates for LA fermentation, except for apple pomace. Results and discussion: A 5-cycle repeated batch fermentation was conducted to optimize waste utilization and production, resulting in a total of 180.56 g/L of LA with a volumetric productivity of 0.88 g/L∙h. Subsequently, mechanical filtration and enzymatic hydrolysis were attempted. The total amount of LA produced in the 5-cycle repeated batch process was 397.1 g/L over 288 h, achieving a volumetric productivity of 1.32 g/L∙h. These findings suggest a promising biorefinery process for low-cost LA production from agri-food wastes.

The role of fermentation with lactic acid bacteria in quality and health effects of plant-based dairy analogues

The modern food industry is undergoing a rapid change with the trend of production of plant-based food products that are more sustainable and have less impact on nature. Plant-based dairy analogues have been increasingly popular due to their suitability for individuals with milk protein allergy or lactose intolerance and those preferring a plant-based diet. Nevertheless, plant-based products still have insufficient nutritional quality, undesirable structure, and earthy, green, and bean-like flavor compared to dairy products. In addition, most plant-based foods contain lesser amounts of essential nutrients, antinutrients limiting the bioavailability of some nutrients, and allergenic proteins. Novel processing technologies can be applied to have a homogeneous and stable structure. On the other hand, fermentation of plant-based matrix with lactic acid bacteria can provide a solution to most of these problems. Additional nutrients can be produced and antinutrients can be degraded by bacterial metabolism, thereby increasing nutritional value. Allergenic proteins can be hydrolyzed reducing their immunoreactivity. In addition, fermentation has been found to reduce undesired flavors and to enhance various bioactivities of plant foods. However, the main challenge in the production of fermented plant-based dairy analogues is to mimic familiar dairy-like flavors by producing the major flavor compounds other than organic acids, yielding a flavor profile similar to those of fermented dairy products. Further studies are required for the improvement of the flavor of fermented plant-based dairy analogues through the selection of special microbial cultures and formulations.

Galactooligosaccharides: Synthesis, metabolism, bioactivities and food applications

Prebiotics are non-digestible ingredients that exert significant health-promoting effects on hosts. Galactooligosaccharides (GOS) have remarkable prebiotic effects and structural similarity to human milk oligosaccharides. They generally comprise two to eight sugar units, including galactose and glucose, which are synthesized from substrate lactose by microbial β-galactosidase. Enzyme sources from probiotics have received particular interest because of their safety and potential to synthesize specific structures that are particularly metabolized by intestinal probiotics. Owing to advancements in modern analytical techniques, many GOS structures have been identified, which vary in degree of polymerization, glycosidic linkage, and branch location. After intake, GOS adjust gut microbiota which produce short chain fatty acids, and exhibit excellent biological activities. They selectively stimulate the proliferation of probiotics, inhibit the growth and adhesion of pathogenic bacteria, alleviate gastrointestinal, neurological, metabolic and allergic diseases, modulate metabolites production, and adjust ion storage and absorption. Additionally, GOS are safe and stable, with high solubility and clean taste, and thus are widely used as food additives. GOS can improve the appearance, flavor, taste, texture, viscosity, rheological properties, shelf life, and health benefits of food products. This review systemically covers GOS synthesis, structure identifications, metabolism mechanisms, prebiotic bioactivities and wide applications, focusing on recent advances.

Effect of sugar content on characteristic flavour formation of tomato sour soup fermented by Lacticaseibacillus casei H1 based on non-targeted metabolomics analysis

To reveal the formation mechanism of the characteristic flavour of tomato sour soup (TSS), metabolomics based on UHPLC-Q-TOF/MS was used to investigate the effect of sugar addition on TSS metabolomics during fermentation with Lacticaseibacillus casei H1. A total of 254 differentially abundant metabolites were identified in the 10% added-sugar group, which mainly belonged to organic acids and derivatives, fatty acyls, and organic oxygen compounds. Metabolic pathway analysis revealed that alanine aspartate and glutamate metabolism, valine leucine and isoleucine metabolism and butanoate metabolism were the potential pathways for the flavour of TSS formation. Lactic acid, acetic acid, Ala, Glu and Asp significantly contributed to the acidity and umami formation of TSS. This study showed that sugar regulation played an important role in the formation of the characteristic TSS flavour during fermentation, providing important support for understanding the formation mechanism of organic acids as the main characteristic flavour of TSS.

Food peptidomic analysis of bovine milk fermented by Lacticaseibacillus casei LBC 237: In silico prediction of bioactive peptides and anticancer potential

Bioactive peptides, which exhibited diverse biological activities such as anti-cancer, anti-inflammatory, bactericidal, antiviral, and quorum sensing properties, were considered promising alternative therapeutic agents. Sourced from various raw materials, particularly foods, these peptides garnered significant interest. In this context, the study focused on exploring bioactive peptides derived from bovine whole milk fermentation by Lacticaseibacillus casei LBC 237. Comprehensive peptidomic analysis and in silico predictions, with a specific emphasis on anti-cancer properties, were conducted. The study categorized peptides into BP-LBC, originating from the metabolism of L. casei LBC 237 and not matching any sequence in the Bos taurus database, and BP-MILK, matching a sequence in the Bos taurus database. Among the 143 identified peptides with potential biological activity, 33.56% were attributed to BP-LBC, while 66.43% originated from BP-MILK, demonstrating the important contribution of proteins in bovine milk in the generation of bioactive peptides. Hydrophobic peptides, enriched in Leucine, Lysine, and Proline, dominated both fractions, significantly influencing their functional properties. Pearson correlation analysis revealed inverse relationships between bioactive peptides, molecular weight, and anti-tumor activity in BP-MILK. The DGKVWEESLK peptide exhibited in silico activity against 10 different cancer cell lines. Studying the bioactive properties of peptides from familiar sources enhances the connection between food science and human health. In addition, in silico studies have been crucial in deepening our understanding of the bioactive potential of these peptides and their mode of action.

CRISPR-Cas systems of lactic acid bacteria and applications in food science

CRISPR-Cas (Clustered regularly interspaced short palindromic repeats-CRISPR associated proteins) systems are widely distributed in lactic acid bacteria (LAB), contributing to their RNA-mediated adaptive defense immunity. The CRISPR-Cas-based genetic tools have exhibited powerful capability. It has been highly utilized in different organisms, accelerating the development of life science. The review summarized the components, adaptive immunity mechanisms, and classification of CRISPR-Cas systems; analyzed the distribution and characteristics of CRISPR-Cas system in LAB. The review focuses on the development of CRISPR-Cas-based genetic tools in LAB for providing latest development and future trend. The diverse and broad applications of CRISPR-Cas systems in food/probiotic industry are introduced. LAB harbor a plenty of CRISPR-Cas systems, which contribute to generate safer and more robust strains with increased resistance against bacteriophage and prevent the dissemination of plasmids carrying antibiotic-resistance markers. Furthermore, the CRISPR-Cas system from LAB could be used to exploit novel, flexible, programmable genome editing tools of native host and other organisms, resolving the limitation of genetic operation of some LAB species, increasing the important biological functions of probiotics, improving the adaptation of probiotics in complex environments, and inhibiting the growth of foodborne pathogens. The development of the genetic tools based on CRISPR-Cas system in LAB, especially the endogenous CRISPR-Cas system, will open new avenues for precise regulation, rational design, and flexible application of LAB.

Lacticaseibacillus paracasei CCFM1222 Ameliorated the Intestinal Barrier and Regulated Gut Microbiota in Mice with Dextran Sulfate Sodium-Induced Colitis

Lacticaseibacillus paracasei has been regarded as a probiotic bacterium because of its role in anti-inflammatory properties and maintenance of intestinal barrier permeability. Here, we explored the anticolitic effects and mechanism of L. paracasei CCFM1222. The results showed that L. paracasei CCFM1222 supplementation could suppress the disease activity index (DAI) and colon length shortening in colitis mice, accompanied by a moderate increase in colonic tight junction proteins (ZO-1, occludin and claudin-1). L. paracasei CCFM1222 intervention significantly suppressed the levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) and significantly elevated the activities of antioxidant enzymes (including SOD, GSH-Px, and CAT) in the colon by regulating the TLR4/MyD88/NF-κB and Nrf2 signaling pathways in colitis mice. In addition, L. paracasei CCFM1222 significantly shifted the gut microbiota, including elevating the abundance of Catabacter, Ruminiclostridium 9, Alistipes, and Faecalibaculum, as well as reducing the abundance of Mucispirillum, Escherichia-Shigella, and Salmonella, which was associated with the improvement of colonic barrier damage. Overall, these results suggest that L. paracasei CCFM1222 is a good candidate for probiotic of improving colonic barrier damage and associated diseases.

Probiotic-loaded seed mucilage-based edible coatings for fresh pistachio fruit preservation: an experimental and modeling study

In this study, Lallemantia royleana mucilage (LRM) based edible coating containing 1.5 × 108 and 3 × 109 CFU/mL Lacticaseibacillus casei XN18 (Lbc1.5 and Lbc3) was designed to improve the quality and shelf-life of fresh pistachio. The fresh pistachios were coated with LRM + Lbc and their physicochemical, microbial, and sensory properties were evaluated after 1-, 5-, 15-, 25-, and 35-day storage at 4 °C. By the end of storage day, in comparison to control, the presence of probiotic isolate in the edible coating (particularly LRM + Lbc3) led to a marked decrease in fungal growth (3.1 vs. 5.8 Log CFU/g), weight loss (6.7 vs. 8.1%), and fat oxidation (0.19 vs. 0.98 meq O2/kg), and preserved total chlorophylls (8.1 vs. 5.85 mg/kg) and phenols (31.5 vs. 20.32 mg GAE/100 g), and antioxidant activity (38.95 vs. 15.18%) of samples during storage period. Furthermore, LRM + Lbc3-coated samples had a probiotic number above the recommended level (6.85-9.29 log CFU/g) throughout storage. The pistachios coated with probiotic-enriched edible coatings were greatly accepted by panelists. In the next section, Gaussian Process Regression (GPR) was used for predicting some parameters including: weight loss, TSS, Fat content, PV, Soluble carbohydrate content, Viability, Total phenolic compounds, Antioxidant activity, Mold and yeast, Total chlorophylls, Total carotenoids, Color, Odor and Overall acceptance. The results indicated that, there is a good agreement between the actual and predicted data by GPR model and it can be used for similar situation to decrease the cost of laboratory tests and increase the respond of analysis.

Isolation, Characterization, and Safety Evaluation of the Novel Probiotic Strain Lacticaseibacillus paracasei IDCC 3401 via Genomic and Phenotypic Approaches

This study aimed to explore the safety and properties of Lacticaseibacillus paracasei IDCC 3401 as a novel probiotic strain via genomic and phenotypic analyses. In whole-genome sequencing, the genes associated with antibiotic resistance and virulence were not detected in this strain. The minimum inhibitory concentration test revealed that L. paracasei IDCC 3401 was susceptible to all the antibiotics tested, except for kanamycin. Furthermore, the strain did not produce toxigenic compounds, such as biogenic amines and D-lactate, nor did it exhibit significant toxicity in a single-dose acute oral toxicity test in rats. Phenotypic characterization of carbohydrate utilization and enzymatic activities indicated that L. paracasei IDCC 3401 can utilize various nutrients, allowing it to grow in deficient conditions and produce health-promoting metabolites. The presence of L. paracasei IDCC 3401 supernatants significantly inhibited the growth of enteric pathogens (p < 0.05). In addition, the adhesion ability of L. paracasei IDCC 3401 to intestinal epithelial cells was found to be as superior as that of Lacticaseibacillus rhamnosus GG. These results suggest that L. paracasei IDCC 3401 is safe for consumption and provides health benefits to the host.

Structural elucidation and physicochemical properties of litchi polysaccharide with the promoting effect on exopolysaccharide production by Weissella confusa

Exopolysaccharide (EPS), as a secondary metabolite of microorganisms, has been commonly used in the dairy industry to replace the traditional stabilizers. However, the EPS production by microorganism is generally low, which limits its application. A litchi polysaccharide (Lzp2-2) with the promoting effect on EPS production by Weissella confusa was purified. The SEM and FT-IR analysis indicated that Lzp2-2 displayed a compact netlike structure and typical bands of carbohydrates. The structure of Lzp2-2 was further elucidated, which was comprised of a major backbone structure [→3)-β-D-Galp-(1→6)-β-D-Galp-(1 → 6)-β-D-Galp-(1 → 3)-β-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 3)-α-D-Glcp-(1→] linked with two side chains [α-L-Araf-(1 → 5)-α-L-Araf-(1→, and β-D-Glcp-(1 → or α-L-Araf-(1→] at the O-3 and O-6) of β-D-Galp-(1→, respectively. Finally, Lzp2-2 was applied as an additive to the medium of yoghurt fermented by W. confusa. The results indicated Lzp2-2 not only promoted the EPS production to improve the viscosity, texture and mouthfeel of yoghurt, but also facilitated the generation of other secondary metabolites (volatile organic compounds), thus elevating the flavor of yoghurt.

The quest for the perfect loaf of sourdough bread continues: Novel developments for selection of sourdough starter cultures

Sourdough fermentation, one of the oldest unit operations in food production, is currently experiencing a revival in bread production at the household, artisanal, and the industrial level. The expanding use of sourdough fermentation in bread production and the adaptation of fermentation to large scale industrial bread production also necessitate the development of novel starter cultures. Developments in the last years also have expanded the tools that are used to assess the metabolic potential of specific strains, species or genera of the Lactobacillaceae and have identified multiple ecological and metabolic traits as clade-specific. This review aims to provide an overview on the clade-specific metabolic potential of members of the Lactobacillaceae for use in sourdough baking, and the impact of these clade-specific traits on bread quality. Emphasis is placed on carbohydrate metabolism, including the conversion of sucrose and starch to soluble polysaccharides, conversion of amino acids, and the metabolism of organic acids. The current state of knowledge to compose multi-strain starter cultures (synthetic microbial communities) that are suitable for back-slopping will also be discussed. Taken together, the communication outlines the current tools for selection of microbes for use in sourdough baking.

New progress in the identifying regulatory factors of exopolysaccharide synthesis in lactic acid bacteria

The exopolysaccharides (EPSs) of lactic acid bacteria (LAB) have presented various bioactivities and beneficial characteristics, rendering their vast commercial value and attracting a broad interest of researchers. The diversity of EPS structures contributes to the changes of EPS functions. However, the low yield of EPS of LAB has severely limited these biopolymers' comprehensive studies and applications in different areas, such as functional food, health and medicine fields. The clarification of biosynthesis mechanism of EPS will accelerate the synthesis and reconstruction of EPS. In recent years, with the development of new genetic manipulation techniques, there has been significant progress in the EPS biosynthesis mechanisms in LAB. In this review, the structure of LAB-derived EPSs, the EPS biosynthesis basic pathways in LAB, the EPS biosynthetic gene cluster, and the regulation mechanism of EPS biosynthesis will be summarized. It will focus on the latest progress in EPS biosynthesis regulation of LAB and provide prospects for future related developments.

The digestive behavior of pectin in human gastrointestinal tract: a review on fermentation characteristics and degradation mechanism

Pectin is widely spread in nature and it develops an extremely complex structure in terms of monosaccharide composition, glycosidic linkage types, and non-glycosidic substituents. As a non-digestible polysaccharide, pectin exhibits resistance to human digestive enzymes, however, it is easily utilized by gut microbiota in the large intestine. Currently, pectin has been exploited as a novel functional component with numerous physiological benefits, and it shows a promising prospect in promoting human health. In this review, we introduce the regulatory effects of pectin on intestinal inflammation and metabolic syndromes. Subsequently, the digestive behavior of pectin in the upper gastrointestinal tract is summarized, and then it will be focused on pectin's fermentation characteristics in the large intestine. The fermentation selectivity of pectin by gut bacteria and the effects of pectin structure on intestinal microecology were discussed to highlight the interaction between pectin and bacterial community. Meanwhile, we also offer information on how gut bacteria orchestrate enzymes to degrade pectin. All of these findings provide insights into pectin digestion and advance the application of pectin in human health.

Effects of Lactobacillus fermentation on Eucheuma spinosum polysaccharides: Characterization and mast cell membrane stabilizing activity

Eucheuma polysaccharides have varieties of biological activities. However, it is accompanied by problems like large molecular weight, high viscosity, and low utilization. Here, we first prepared fermented Eucheuma spinosum polysaccharides (F-ESP) by Lactobacillus fermentation, compared with low-temperature freeze-thaw ESP (L-ESP) prepared by the freeze-thaw method, explored the composition and structural characteristics of F-ESP and L-ESP, and evaluation of the ability of different samples to inhibit mast cell degranulation using classical mast cell model. Then, the activity of L-ESP and F-ESP in vivo was preliminarily evaluated using a passive cutaneous anaphylaxis model. Two kinds of F-ESP named F1-ESP-3 and F2-ESP-3 were obtained by fermentation of Eucheuma spinosum with the selected strains of Lactobacillus.sakei subsp.sakei and Lactobacillus.rhamnosus. Compared with the purified component L-ESP-3, the monosaccharide composition of F1-ESP-3 contains more glucuronic acid, the molecular weight reduced from >600 kDa (L-ESP-3) to 28.30 kDa (F1-ESP-3) and 33.58 kDa (F2-ESP-3), F1-ESP-3 has higher solubility and lower apparent viscosity. Fermentation did not destroy the functional groups and structure of ESP. Moreover, F1-ESP-3 significantly inhibited RBL-2H3 cell degranulation by reducing depolymerization of F-actin and Ca²⁺ influx. F1-ESP-3 reduced the symptoms of mast cell-mediated passive cutaneous anaphylaxis, indicating that F1-ESP-3 may have better anti-allergic activity in vivo.

Inulin increases the EPS biosynthesis of Lactobacillus delbrueckii ssp. bulgaricus LDB-C1

OBJECTIVE

Its eps gene cluster, the antioxidant activity and monosaccharide composition of exopolysaccharides, the expression levels of related genes at different fermentations were analyzed for clarifying the exopolysaccharide biosynthesis mechanism of Lactobacillus delbrueckii subsp. bulgaricus LDB-C1.

RESULTS

The comparison analysis of eps gene clusters indicated that the gene clusters present diversity and strain specificity. The crude exopolysaccharides from LDB-C1 exhibited a good antioxidant activity. Compared with glucose, fructose, galactose, and fructooligosaccharide, inulin significantly improved the exopolysaccharide biosynthesis. The structures of EPSs were significantly different under different carbohydrate fermentation conditions. Inulin obviously increased the expressions of most EPS biosynthesis related genes at fermentation 4 h.

CONCLUSION

Inulin accelerated the beginning of the exopolysaccharide production in LDB-C1, and the enzymes promoted by inulin was beneficial for the accumulation of exopolysaccharide at the whole fermentation process.

Journey of the Probiotic Bacteria: Survival of the Fittest

This review aims to bring a more general view of the technological and biological challenges regarding production and use of probiotic bacteria in promoting human health. After a brief description of the current concepts, the challenges for the production at an industrial level are presented from the physiology of the central metabolism to the ability to face the main forms of stress in the industrial process. Once produced, these cells are processed to be commercialized in suspension or dried forms or added to food matrices. At this stage, the maintenance of cell viability and vitality is of paramount for the quality of the product. Powder products requires the development of strategies that ensure the integrity of components and cellular functions that allow complete recovery of cells at the time of consumption. Finally, once consumed, probiotic cells must face a very powerful set of physicochemical mechanisms within the body, which include enzymes, antibacterial molecules and sudden changes in pH. Understanding the action of these agents and the induction of cellular tolerance mechanisms is fundamental for the selection of increasingly efficient strains in order to survive from production to colonization of the intestinal tract and to promote the desired health benefits.

Macroalgal biomass as a potential resource for lactic acid fermentation

Lactic acid is an essential platform chemical with various applications in the chemicals, food, pharmaceutical, and cosmetic industries. Currently, the demand for lactic acid is driven by the role of lactic acid as the starting material for the production of bioplastic polylactide. Microbial fermentation for lactic acid production is favored due to the production of enantiomerically pure lactic acid required for polylactide synthesis, as opposed to the racemic mixture obtained via chemical synthesis. The utilization of first-generation feedstock for commercial lactic acid production is challenged by feedstock costs and sustainability issues. Macroalgae are photosynthetic benthic aquatic plants that contribute tremendously towards carbon capture with subsequent carbon-rich biomass production. Macroalgae are commercially cultivated to extract hydrocolloids, and recent studies have focused on applying biomass as a fermentation feedstock. This review provides comprehensive information on the design and development of sustainable and cost-effective, algae-based lactic acid production. The central carbon regulation in lactic acid bacteria and the metabolism of seaweed-derived sugars are described. An exhaustive compilation of lactic acid fermentation of macroalgae hydrolysates revealed that lactic acid bacteria can effectively ferment the mixture of sugars present in the hydrolysate with comparable yields. The environmental impacts and economic prospects of macroalgal lactic acid are analyzed. Valorization of the vast amounts of spent macroalgal biomass residue post hydrocolloid extraction in a biorefinery is a viable strategy for cost-effective lactic acid production.

Effects of post-fermentation on the flavor compounds formation in red sour soup

Red Sour Soup (RSS) is a traditional fermented food in China. After two rounds of fermentation, sour soup has a mellow flavor. However, the microbial composition and flavor formation processes in post-fermentation in RSS are unclear. This study investigates the bacteria composition of RSS during the post-fermentation stage (0–180 days) using high-throughput sequencing. The results show that lactic acid bacteria (LAB) are dominant during the post-fermentation process, and their abundance gradually increases with fermentation time. Additionally, gas chromatography-mass spectrometry was used to detect volatile flavor compounds in the post-fermentation process. Seventy-seven volatile flavor compounds were identified, including 24 esters, 14 terpenes, 9 aromatic hydrocarbons, 9 alkanes, 6 heterocyclic compounds, 3 alcohols, 3 acids, 3 ketones, 2 phenols, 2 aldehydes, 1 amine, and 1 other. Esters and aromatic hydrocarbons are the main volatile compounds in RSS during the post-fermentation process. Orthogonal partial least squares screening and correlation analysis derived several significant correlations, including 48 pairs of positive correlations and 19 pairs of negative correlations. Among them, Acetobacter spp., Clostridium spp. and Sporolactobacillus spp. have 15, 14, 20 significant correlation pairs, respectively, and are considered the most important bacterial genera post-fermentation. Volatile substances become abundant with increasing fermentation time. LAB are excessive after more than 120 days but cause a drastic reduction in volatile ester levels. Thus, the post-fermentation time should be restricted to 120 days, which retains the highest concentrations of volatile esters in RSS. Overall, these findings provide a theoretical basis to determine an optimal post-fermentation time duration, and identify essential bacteria for manufacturing high-quality starter material to shorten the RSS post-fermentation processing time.

Comparative genomic analysis of Lacticaseibacillus paracasei SMN-LBK from koumiss

Lacticaseibacillus paracasei SMN-LBK, which was isolated in Xinjiang, has been shown to be a probiotic strain and used as the auxiliary starter for dairy fermentation. Comparative genomic analysis was performed to investigate the metabolic preference and ethanol tolerance mechanisms of L. paracasei SMN-LBK. The results of comparative genomics showed that L. paracasei strains had high conservation and genetic diversity. SMN-LBK encoded various genes related to carbohydrate and amino acid metabolism pathways, which endow this strain with good fermentation potential. In addition, 6 CRISPR sequences and 8 cas proteins were found in SMN-LBK, and these could play vital roles in the immune system. Furthermore, a unique cluster of potential secondary metabolism genes related to bacteriocins was detected in the genome of SMN-LBK, and this could be important for the preservation of fermented foods. Multiple genes related to alcohol tolerance were also identified. In conclusion, our study explained the traits that were previously demonstrated for SMN-LBK as phenotypes and provided a theoretical basis for the application of SMN-LBK in the food industry.

The antimicrobial and bioactive properties of lactobionic acid

Lactobionic acid (LBA) is a bioactive molecule that has generated keen interest in different industries. However, its future application in the food area is one of the most promising. Chemically, it is a polyhydroxy acid formed by the union of two molecules (galactose and gluconic acid) linked by an ether-bond, showing many interesting and unusual properties due to its structure and composition, although it is traditionally known in the food industry for its chelating, moisturizing, gelling, and antioxidant properties. There has been much research into the production of LBA, either by microbial fermentation or biocatalytic approaches such as enzymatic synthesis, but its use in foodstuffs, to produce new functional products and to evaluate its antimicrobial activity against food-borne pathogens, is a relatively new topic that has attracted the interest of the international research community recently. Furthermore, in spite of the potential of LBA, it has been approved only by the US Food and Drug Administration, and for its use as the salt form, but the publication of new comprehensive studies, able to agglutinate all the new food-related LBA research results, could disseminate knowledge about this compound and have an influence on its current regulation status. The aim of the present review is to describe the most recent advances and research on its antimicrobial potential, as well as summarizing the significant aspects that make LBA a promising bioactive compound for the food sector. © 2022 Society of Chemical Industry.

Effect of Coix Seed Extracts on Growth and Metabolism of Limosilactobacillus reuteri

Coix seed (Coix lachryma-jobi L.) is an important nourishing food and traditional Chinese medicine. The role of their bioactive constituents in physiology and pharmacology has received considerable scientific attention. However, very little is known about the role of coix seed bioactive components in the growth of Limosilactobacillus reuteri (L. reuteri). This study aimed to evaluate the effects of coix seed extract (CSE) on the growth, acidifying activity, and metabolism of L. reuteri. The results showed that CSE can increase the growth and acidifying activity of L. reuteri compared with the control group. During the stationary phase, the viable bacteria in the medium supplemented with coix seed oil (CSO, 13.72 Log₁₀ CFU/mL), coix polysaccharide (CPO, 12.24 Log₁₀ CFU/mL), and coix protein (CPR, 11.91 Log₁₀ CFU/mL) were significantly higher (p < 0.05) than the control group (MRS, 9.16 Log₁₀ CFU/mL). CSE also enhanced the biosynthesis of lactic acid and acetic acid of L. reuteri. Untargeted metabolomics results indicated that the carbohydrate metabolism, amino acid metabolism, and nucleotide metabolism activities of L. reuteri were increased after adding CSE. Furthermore, CSE increased the accumulation of bioactive metabolites, such as phenyl lactic acid, vitamins, and biotin. Overall, CSE may have prebiotic potential and can be used to culture L. reuteri with high viable bacteria.

The Carbohydrate Metabolism of Lactiplantibacillus plantarum

Lactiplantibacillus plantarum has a strong carbohydrate utilization ability. This characteristic plays an important role in its gastrointestinal tract colonization and probiotic effects. L. plantarum LP-F1 presents a high carbohydrate utilization capacity. The genome analysis of 165 L. plantarum strains indicated the species has a plenty of carbohydrate metabolism genes, presenting a strain specificity. Furthermore, two-component systems (TCSs) analysis revealed that the species has more TCSs than other lactic acid bacteria, and the distribution of TCS also shows the strain specificity. In order to clarify the sugar metabolism mechanism under different carbohydrate fermentation conditions, the expressions of 27 carbohydrate metabolism genes, catabolite control protein A (CcpA) gene ccpA, and TCSs genes were analyzed by quantitative real-time PCR technology. The correlation analysis between the expressions of regulatory genes and sugar metabolism genes showed that some regulatory genes were correlated with most of the sugar metabolism genes, suggesting that some TCSs might be involved in the regulation of sugar metabolism.

Influence of Oat β-Glucan on the Survival and Proteolytic Activity of Lactobacillus rhamnosus GG in Milk Fermentation: Optimization by Response Surface

β-glucans come from cereals that have been located within compounds with prebiotic activity. They have presented several bioactivities that have determined their high functional value. The aim of this study was to identify the influence of oat β-glucan on the survival and proteolytic activity of Lactobacillus rhamnosus GG in a milk fermentation through an experimental design to optimize the process. For β-glucan extraction after dry milling of oats, two methods were applied: with and without enzymatic inactivation of the semolina. The highest extraction yield (45.25 g/L) was obtained with enzymatic inactivation. For the optimization of survival and proteolytic activity, a central design composed of axial points with two factors on three levels was used. Control factors were β-glucan and inoculum concentrations. According to response surface, the best survival growth rate of probiotic was observed with 4.38% of inoculum and 22.46 g/L of β-glucan, and the highest production of free amino groups was observed with 4.18% of inoculum and 22.71 g/L of β-glucan. Thus, β-glucan promotes the proteolytic activity of Lb. rhamnosus GG in milk fermentation.