The effect of optimized carbon source on the synthesis and composition of exopolysaccharides produced by Lactobacillus paracasei

Proteome trade-off between primary and secondary metabolism shapes acid stress induced bacterial exopolysaccharide production

Bacterial exopolysaccharide (EPS), as a high-value probiotic product, is known to be biosynthesized by a secondary metabolic pathway to mediate acid stress in lactic acid bacteria. However, a quantitative understanding of cellular resource coordination underlying acid stress-induced EPS production remains lacking. Systematically investigating Lactiplantibacillus plantarum HMX2, a well acknowledged EPS-producer, this study measured growth phenotypes, metabolomics, and proteomics of the target strain cultured at different pH values. Multi-omics analysis demonstrated that the EPS biosynthetic pathway was significantly up-regulated under acid stress, and pinpointed Fur as the most probable controlling transcriptional factor. Furthermore, the experimentally observed proteome re-allocation between primary metabolism and EPS biosynthesis was effectively captured by the regulatory proteome constrained flux balance analysis (RPCFBA) model via incorporating an activation function for secondary metabolism. This work, fusing the power of multi-omics analysis and genome-scale metabolic modeling, quantitatively elucidated the proteome trade-off between cellular growth and stress resistance underlying EPS production in lactic acid bacteria and shed light on the control principle of microbial secondary metabolism.

Optimization of the enrichment medium for recombinant ChIL-4-ChIL-2 in Lactococcus lactis through response surface methodology

Coccidiosis, caused by Eimeria, represents a significant challenge to the poultry industry and leads to significant economic losses to the poultry industry. Traditional anticoccidial drugs is diminishing due to drug resistance, and although live vaccines are an effective preventive and treatment means, they may cause mild infections and affect weight gain when used. Recombinant ChIL-4-ChIL-2 in Lactococcus lactis, as a new type of food-grade recombinant cytokine immunoadjuvant, characterized by its ability to enhance the immunological efficacy of live vaccines against chicken coccidiosis. In this study, using the OD600 value of the culture broth of ChIL-4-ChIL-2 in Lactococcus lactis as the index, the optimal combination of carbon and nitrogen sources and inorganic salts in the medium was determined through single-factor experiments, and the medium formula was optimized using Box-Behnken design and response surface analysis. The results of single-factor experiments indicated that the optimal carbon source, nitrogen source, and buffer salt addition amounts in the M17 medium for recombinant ChIL-4-ChIL-2 in Lactococcus lactis were as follows: 1 % mixed carbon source (with a trehalose to glucose ratio of 1:1), 7 % yeast extract powder as the nitrogen source, and 0.5 % potassium dihydrogen phosphate-sodium hydroxide as the buffer salt. Furthermore, the results of response surface methodology experiments indicate that the optimal medium formulation for recombinant ChIL-4-ChIL-2 in Lactococcus lactis is M17 medium supplemented with 1 % carbon source (glucose: trehalose = 1:1), 8 % nitrogen source (yeast extract powder), and 0.8 % buffer salts (potassium dihydrogen phosphate-sodium hydroxide). This optimized medium can significantly increase the yield of recombinant ChIL-4-ChIL-2 in Lactococcus lactis, and the OD600 value of the cell density can reach 1.103. This optimized medium provides a scientific foundation for developing a production process aimed at the large-scale production of recombinant ChIL-4-ChIL-2 in Lactococcus lactis.

Metabolic Engineering of Escherichia coli for the Improved Malonic Acid Production

Malonic acid (MA) is a high-value chemical with diverse applications in the fields of food, agriculture, medicine, and chemical synthesis. Despite the successful biosynthesis of MA has been performed in Escherichia coli, Myceliophthora thermophila, and Saccharomyces cerevisiae, the resulting MA titers remain insufficient for industrial-scale production. In this study, three distinct metabolic pathways were designed and constructed to increase MA production in E. coli. Among these, the fumaric acid pathway comprising four key enzymes including the aspartase (AspA), the decarboxylase (PanD), the β-alanine-pyruvate transaminase (Pa0132), and the succinic aldehyde dehydrogenase (YneI) was identified as the most effective for MA production. Additionally, the supplementation of fumaric acid was found to significantly improve MA production. To further enhance the MA production, metabolic engineering strategies were employed, including the deletion of the ydfG gene, responsible for encoding the malonic semialdehyde reductase, and the ptsG gene, which encodes a glucose transporter. Finally, through the optimization of fermentation conditions and feeding strategies, the engineered strain achieved an MA titer of 1.4 g/L in shake flask and 17.8 g/L in fed-batch fermentation. This study provides new insights into the industrial-scale production of MA utilizing the metabolically engineered E. coli cells.

Sucrose improve Lactiplantibacillus plantarum LIP-1's tolerance to heat by increasing biofilm production

Optimizing the carbon source to increase biofilm production and thus boost the heat tolerance of strains is a promising strategy. However, related research is scarce. This study investigated the effects of varying glucose and sucrose amounts added to MRS medium on biofilm production and heat tolerance by Lactiplantibacillus plantarum LIP-1. Transcriptomic, proteomic, and metabolomic approaches were combined to analyze the intrinsic mechanism underlying the sucrose-induced increase in biofilm production. We then investigated the protective role of the biofilm for the strain. Compared with the control group (2 % glucose), biofilm production in the experimental group (2 % glucose+2 % sucrose) increased by 27 %, and after heat treatment (75 °C for 40 s), the experimental group demonstrated a 38 % increase in heat tolerance. Multiomic results unveiled that biofilm synthesis-related metabolism pathways were altered in the experimental group compared with the control group. When the expression of key genes and the enzymes they encode(sacA, metC, mccB, and CTH) was upregulated, L-homocysteine was synthesized. According to metabolomics results, the L-homocysteine content in the experimental group increased to twice that in the control group. This resulted in a 37 % increase in the extracellular protein content of biofilms. The biofilm inhibition test confirmed that this increase in extracellular protein content was the primary factor augmenting the strain's heat tolerance. The findings suggested that adding sucrose to MRS medium for boosting biofilm production is a viable technical approach that enhances cell tolerance to heat.

Lead biosorption and chemical composition of extracellular polymeric substances isolated from mixotrophic microalgal cultures

Extracellular polymers (EPS) produced by microalgae are considered an important factor in the process of biosorption of environmental contaminants. The study investigated the impact of mixotrophic cultivation of unicellular algae Chlorella vulgaris, Parachlorella kessleri, and Vischeria magna on the specific productivity and yield of total and soluble EPS as well as the biochemical composition and sorption properties of extracellular polymers in order to explore their potential to be used for biosorption. The results showed that the mixotrophic conditions enhanced the productivity and contributed to changes in the biochemical and monomer composition of EPS. Higher levels of total sugars, reducing sugars, protein, and phenolic compounds and reduced content of uronic acids were observed in the EPS isolated in the mixotrophic conditions. Rhamnose, xylose, mannose, glucose, and galactose were detected in the mixotrophic EPS samples. FTIR and ICP-OES were applied to characterise the structure of EPS and their role in Pb(II) removal. The results showed that the carboxyl groups and hydroxyl groups observed in the mixotrophic EPS played an important role in the Pb(II) sorption process. The EPS from the mixotrophic C. vulgaris cultures showed the highest potential for the removal of Pb(II) and the highest sorption capacity.

Current state, challenges and future orientations of the applications of lactic acid bacteria exopolysaccharide in foods

In the quest for a balanced diet and better health, the global shift towards nutrient-dense foods highlights the multiple roles of lactic acid bacteria exopolysaccharides (LAB-EPS) in improving food quality and health. This paper offers a comprehensive survey of LAB-EPS, focusing on their classification, biosynthesis pathways and application in the food industry, from dairy products to bakery products and meat. It highlights the impact of LAB-EPS on the texture and sensory qualities of food. Despite their promising prospects, these polysaccharides face various application challenges in the food industry. These include variability in EPS production among LAB strains, complexity in structure-function relationships, and limited understanding of their health benefits. In order to address these issues, the review identifies and suggests future research directions to optimize the production of LAB-EPS, elucidating their health benefit mechanisms, and expanding their application scope. In summary, this review aims to contribute to advance innovation and progress in the food industry by developing healthier food options and deepening the understanding of LAB-EPS in promoting human health.

Lactic Acid Bacteria Exopolysaccharides Unveiling Multifaceted Insights from Structure to Application in Foods and Health Promotion

Lactic acid bacteria (LAB) exopolysaccharides (EPSs) have garnered significant scientific interest due to their multifaceted roles in food technology and health promotion. This comprehensive review systematically examines the structural classification of LAB EPSs, emphasizing distinctions between homo-and heteropolysaccharides, as well as the influence of substituent groups (e. g., acetyl, phosphate) on their physicochemical and bioactive properties. Advanced isolation methodologies, including ethanol precipitation and ultrafiltration, coupled with characterization techniques such as nuclear magnetic resonance (NMR) spectroscopy and atomic force microscopy (AFM), are vital for deciphering their chemical and physical characteristics. The biosynthesis pathway, governed by eps operons and modulated by environmental factors (e.g., carbon sources, Ca2+), are discussed as targets for genetic engineering to enhance yield and functionality. Functionally, LAB EPSs display antioxidant, immunomodulatory, anti-tumor, anti-viral, and anti-biofilm activities, with demonstrated applications as natural additives in the food industry, prebiotics, and drug delivery systems. Despite their potential, challenges such as cost-effective production and regulatory hurdles persist. Future research should prioritize the elucidation of molecular mechanisms, clinical validation of health claims, and sustainable bioprocessing innovations to fully harness the transformative potential of LAB EPSs across food, pharmaceutical, and agricultural industries.

In Vitro Cholesterol-Lowering Bioactivity, Synthetic Pathway, and Structural Characterization of Exopolysaccharide Synthesized by Schleiferilactobacillus harbinensis Z171

A strain identified as Schleiferilactobacillus harbinensis was isolated from Chinese sauerkraut, and its exopolysaccharide (EPS) exhibited excellent in vitro cholesterol-lowering bioactivity. Besides, the whole genome of this strain and the structure characteristics of the purified EPS were investigated in this study. S. harbinensis Z171 presented a strong EPS production capacity, with five nucleotide sugar biosynthesis pathways regulated by an EPS synthesis gene cluster. Structural characterization revealed that the purified fraction F-EPS1A was a neutral polysaccharide with a molecular weight of 6.4 × 104 Da. The structure of F-EPS1A contained a backbone that comprised blocks of four 1,2-linked and three 1,3-linked alpha mannose units. Some 1,2-linked alpha mannose residues were branched at C6 with side chains formed by single alpha mannose or a disaccharide consisting of 1,6-linked alpha mannose residues. The structural characteristics endowed F-EPS1A with a high level of cholesterol-lowering bioactivity. In addition, whole genome analysis indicated that S. harbinensis Z171 possessed a strong EPS production capacity. These findings suggested that the EPS produced by S. harbinensis Z171 could be applied as a potential cholesterol-lowering prebiotic agent or supplement in functional food.

Impact of GOS and 2'-FL on the production and structural composition of membrane-associated exopolysaccharides by B. adolescentis and B. infantis

Bifidobacteria, which are increasingly linked to health benefits to the host, produce structurally complex exopolysaccharides which are considered to be effector molecules responsible for health effects. It is currently not clear how the bacterial growth conditions, and especially the carbon source, affect the structural composition of the EPS. Here we present our investigations into the impact of the addition of 2'-fucosyllactose (2'-FL) and galactooligosaccharides (GOS), which are non-digestible carbohydrates added to infant formula, as the sole carbon source during the growth of B. adolescentis and B. infantis. Intriguingly, B. adolescentis produced EPS with larger molecular weights in the presence of GOS or a mixture of GOS/2'-FL. B. infantis showed increased growth levels in the presence of 2'-FL, and also produced an α-1,4-glucan polymer, whose amount was increased when grown on GOS. These findings highlight the species-specific effects of growth conditions on EPS structures.

Sucrose contributed to the biofilm formation of Tetragenococcus halophilus and changed the biofilm structure

Based on the previous research results that the addition of sucrose in the medium improved the biofilm formation of Tetragenococcus halophilus, the influence of sucrose on biofilm formation was explored. Moreover, the influence of exogenous expression of related genes sacA and galE from T. halophilus on the biofilm formation of L. lactis NZ9000 was investigated. The results showed that the addition of sucrose in the medium improved the biofilm formation, the resistance of biofilm cells to freeze-drying stress, and the contents of exopolysaccharides (EPS) and eDNA in the T. halophilus biofilms. Meanwhile, the addition of sucrose in the medium changed the monosaccharide composition of EPS and increased the proportion of glucose and galactose in the monosaccharide composition. Under 2.5% (m/v) salt stress condition, the expression of gene sacA promoted the biofilm formation and the EPS production of L. lactis NZ9000 with the sucrose addition in the medium and changed the EPS monosaccharide composition. The expression of gene galE up-regulated the proportion of rhamnose, galactose, and arabinose in the monosaccharide composition of EPS, and down-regulated the proportion of glucose and mannose. This study will provide a theoretical basis for regulating the biofilm formation of T. halophilus, and provide a reference for the subsequent research on lactic acid bacteria biofilms.

Investigation on the exopolysaccharide production from blueberry juice fermented with lactic acid bacteria: Optimization, fermentation characteristics and Vis-NIR spectral model

The exopolysaccharide production from blueberry juice fermented were investigated. The highest exopolysaccharide yield of 2.2 ± 0.1 g/L (increase by 32.5 %) was reached under the conditions of temperature 26.5 °C, pH 5.5, inoculated quantity 5.4 %, and glucose addition 9.1 % using the artificial neural network and genetic algorithm. Under the optimal conditions, the viable cell counts and total acids were increased by 2.0 log CFU/mL and 1.6 times, respectively, while the content of phenolics and anthocyanin was decreased by 9.26 % and 7.86 %, respectively. The changes of these components affected the exopolysaccharide biosynthesis. The absorption bands of -OH and -CH associated with the main functional groups of exopolysaccharide were detected by Visible near-infrared spectroscopy. The prediction model based on spectrum results was constructed. Competitive adaptive reweighted sampling and the random forest were used to enhance the model's prediction performance with the value of RC = 0.936 and RP = 0.835, indicating a good predictability of exopolysaccharides content during fermentation.

Assessment of the Safety and Exopolysaccharide Synthesis Capabilities of Bacillus amyloliquefaciens D189 Based on Complete Genome and Phenotype Analysis

Exopolysaccharides (EPS) are natural macromolecular carbohydrates with good functional activity and physiological activities, which can be utilized as an emulsifier, viscosity enhancer, stabilizer, gelling agent, and water retention agent in a wide range of food products. In this study, the whole genome of Bacillus amyloliquefaciens D189, an EPS-producing bacteria, was sequenced. The result showed that D189 contains a single, circular chromosome of 3,963,356 bp with an average GC content of 45.74% and 3996 coding genes. The gene annotation results showed that D189 is a potentially safe strain and confirmed to be safe associated with hemolytic assay, and antibiotic resistance test. Meanwhile, D189 genome possessed 240 genes related to carbohydrate metabolism. More importantly, D189 could transport 9 sugars and contained a complete biosynthetic pathway for 8 nucleotide sugars. Based on the validation experiments, strain D189 could metabolize 8 sugars (glucose, sucrose, trehalose, fructose, cellobiose, maltose, mannitol, and N-acetyl-D-glucosamine) to produce EPS, with the highest yield of 1.212 g/L when sucrose was the carbon source. Therefore, the whole genome sequencing preliminarily elucidated the physiological mechanism of EPS, providing several pathways for engineering D189 to further enhance the yield of EPS.

Challenges and opportunities in bioprocessing of gellan gum: A review

Gellan gum (GG) - the microbial exopolysaccharide is increasingly being adopted into drug development, tissue engineering, and food and pharmaceutical products. In spite of the commercial importance and expanding application horizon of GG, little attention has been directed toward the exploration of novel microbial cultures, development of advanced screening protocols, strain engineering, and robust upstream or downstream processes. This comprehensive review not only attempts to summarize the existing knowledge pool on GG bioprocess but also critically assesses their inherent challenges. The process optimization design augmented with advanced machine learning modeling tools, widely adopted in other microbial bioprocesses, should be extended to GG. The unification of mechanistic insight into data-driven modeling would help to formulate optimal feeding and process control strategies.

Exopolysaccharide from Lacticaseibacillus paracasei alleviates gastritis in Helicobacter pylori-infected mice by regulating gastric microbiota

Introduction

Many probiotics have the ability to produce extracellular polysaccharides (EPS). EPS derived from these probiotics has been confirmed to regulate the host intestinal microecological balance and alleviate the symptoms of diseases caused by gastrointestinal microecological imbalance.

Results

Lactic acid bacteria (LAB) strain with good exopolysaccharide (EPS) producing ability, namely, Lacticaseibacillus paracasei ZFM54 (L. paracasei ZFM54) was screened. The fermentation conditions of L. paracasei ZFM54 for EPS production were optimized. The EPS54 was characterized by chemical component and monosaccharide composition determination, UV, FT-IR and NMR spectra analysis. Cango red, SEM, AFM and XRD analysis were conducted to characterize the structure of EPS54. The EPS54 effectively reduced the colonization of Helicobacter pylori to AGS cells and recovered the cell morphology. EPS54 could also effectively alleviate the gastritis in the H. pylori-infected mice by down-regulating the mRNA expression levels of pro-inflammatory cytokines IL-6, IL-8, IL-1β and TNF-α and up-regulating the mRNA expression of inflammatory cytokine IL-10 in gastric cells. EPS54 was also found to be able to positively regulate the structure of gastric microbiota.

Conclusion

The EPS 54 from L. paracasei ZFM54 can alleviate gastritis in H. pylori-infected mice by modulating the gastric microbiota.

Effects of different stress conditions on the production, bioactivities, physicochemical and structural characteristics of exopolysaccharides synthetized by Schleiferilactobacillus harbinensis Z171

This study systematically investigated the effects of stress conditions including temperature, pH, H2O2, NaCl, antibiotics on the production and in vitro cholesterol-lowering activity of the exopolysaccharide (EPS) synthetized by Schleiferilactobacillus harbinensis Z171. Additionally, the influences of the optimal stress condition combined with different carbon sources on EPS production were examined, shedding light on the structural characteristics, physicochemical properties and bioactivities of EPSs. The results demonstrated that the EPS produced under H2O2 stress was optimal and presented excellent resistance to simulated gastric juice and α-amylase. Three main fractions, denoted as G-EPS1, F-EPS1 and S-EPS1, were isolated by cellulose DEAE-52 chromatography from crude EPSs synthetized using glucose, fructose and sucrose as carbon sources, respectively. Among them, F-EPS1 possessed the highest cholesterol-lowering, antioxidant and hypoglycemic activities, with the highest molecular weight 91.03 kDa, largest particle size 40.14 nm and apparent viscosity 288.2 mPa·s. Three EPSs exhibited irregular sheet-like and granular structures with good thermal stability. Structural characterization of F-EPS1a (a purified fraction from F-EPS1) revealed that it was a mannan mainly composed of →2)-α-D-Manp-(1→, →3)-α-Manp-(1→ and →2,6)-α-D-Manp-(1→ with branch chains containing α-D-Manp-(1→. F-EPS1a has more potential to be a natural cholesterol-lowering, hypoglycemic and antioxidant supplements in the food industry.

Gut bacterium promotes host fitness in special ecological niche by affecting sugar metabolism in Drosophila suzukii

As an important fruit pest of global significance, Drosophila suzukii occupies a special ecological niche, with the characteristics of high sugar and low protein contents. This niche differs from those occupied by other fruit-damaging Drosophila species. Gut bacteria substantially impact the physiology and ecology of insects. However, the contribution of gut microbes to the fitness of D. suzukii in their special ecological niche remains unclear. In this study, the effect of Klebsiella oxytoca on the development of D. suzukii was examined at physiological and molecular levels. The results showed that, after the removal of gut microbiota, the survival rate and longevity of axenic D. suzukii decreased significantly. Reintroduction of K. oxytoca to the midgut of D. suzukii advanced the development level of D. suzukii. The differentially expressed genes and metabolites between axenic and K. oxytoca-reintroduced D. suzukii were enriched in the pathways of carbohydrate metabolism. This advancement was achieved through an increased glycolysis rate and the regulation of the transcript level of key genes in the glycolysis/gluconeogenesis pathway. Klebsiella oxytoca is likely to play an important role in increasing host fitness in their high-sugar ecological niche by stimulating the glycolysis/gluconeogenesis pathway. As a protein source, bacteria can also provide direct nutrition for D. suzukii, which depends on the quantity or biomass of K. oxytoca. This result may provide a new target for controlling D. suzukii by inhibiting sugar metabolism through eliminating the effect of K. oxytoca and thus disrupting the balance of gut microbial communities.

Improved production of lactiplantibacillus plantarum RO30 exopolysaccharide (REPS) by optimization of process parameters through statistical experimental designs

BACKGROUND

In investigating of (exopolysaccharide) EPS from unconventional sources, lactic acid bacteria have a vital role due to their generally recognized as safe (GRAS) status. EPSs have diverse applications such as drug delivery, antimicrobial activity, surgical implants, and many more in many sectors. Despite being important, the main hindrance to the commercial application of these significant biopolymers is low productivity. Therefore, this study primarily focuses on optimizing physio-chemical conditions to maximize the previously produced EPS from probiotic Lactiplantibacillus plantarum RO30 (L. plantarum RO30) using one factor at a time (OFAT) and method Response Surface Methodology (RSM).

RESULTS

The EPS obtained from L. plantarum RO30 named REPS. The medium formulation for REPS production using the OFAT method revealed that sucrose (20 g/L, beef extract (25 g/L), and ammonium sulfate at 4 g/L concentration were the optimum carbon, organic and inorganic nitrogen sources, and REPS yield was increased up to 9.11 ± 0.51 g/L. RSM experiments revealed that, a greatly significant quadratic polynomial attained from the Central Composite Design (CCD) model was fruitful for specifying the most favorable cultural conditions that have significant consequences on REPS yield. The maximal amount of REPS (10.32 g/L) was formed by: sucrose (40 g/L), beef extract (25 g/L), pH (5.5), incubation temperature (30 °C), and incubation period (72 h). A high closeness was obtained between the predicted and experimental values and it displayed the efficiency of the RSM.

CONCLUSION

This study was conducted to reinforce REPS production in the probiotic LAB L. plantarum RO30 by utilizing various experimental parameters. The maximum REPS yield of 10.32 g/L was attained under the circumstances optimized in the study.

The structure, characterization and immunomodulatory potential of exopolysaccharide produced by Planococcus rifietoensis AP-5 from deep-sea sediments of the Northwest Pacific

Polysaccharides derived from microorganisms exhibit diverse structures and bioactivities, making them promising candidates for the treatment of various diseases. However, marine-derived polysaccharides and their activities are relatively little known. In this work, fifteen marine strains were isolated from surface sediments in the Northwest Pacific Ocean for screening of EPS production. Planococcus rifietoensis AP-5 produced a maximum yield of EPS at 4.80 g/L. The purified EPS (referred to as PPS) had a molecular weight of 51,062 Da and contained amino, hydroxyl, and carbonyl groups as its major functional groups. PPS primarily consisted of →3)-α-D-Galp-(1 → 4)-α-D-Manp-(1 → 2)-α-D-Manp-(1 → 4)-α-D-Manp-(1 → 4,6)-α-D-Glcp-(1 → 6)-β-D-Galp-(1→, with a branch consisting of T-β-D-Glcp-(1→. Additionally, surface morphology of PPS was hollow, porous, and sphere-like stack. PPS primarily contained C, N, and O elements, with a surface area of 33.76 m2/g, a pore volume of 0.13 cc/g, and a pore diameter of 1.69 nm, respectively. Based on the TG curve, the degradation temperature of PPS was measured to be 247 °C. Furthermore, PPS demonstrated immunomodulatory activity through dose-dependently upregulating the expression level of cytokines. It significantly enhanced the cytokine secretion at a concentration of 5 μg/mL. To sum up, this study offers valuable insights for screening marine polysaccharide-based immunomodulators.

Microbial Exopolysaccharide Composites in Biomedicine and Healthcare: Trends and Advances

Microbial exopolysaccharides (EPSs), e.g., xanthan, dextran, gellan, curdlan, etc., have significant applications in several industries (pharma, food, textiles, petroleum, etc.) due to their biocompatibility, nontoxicity, and functional characteristics. However, biodegradability, poor cell adhesion, mineralization, and lower enzyme activity are some other factors that might hinder commercial applications in healthcare practices. Some EPSs lack biological activities that make them prone to degradation in ex vivo, as well as in vivo environments. The blending of EPSs with other natural and synthetic polymers can improve the structural, functional, and physiological characteristics, and make the composites suitable for a diverse range of applications. In comparison to EPS, composites have more mechanical strength, porosity, and stress-bearing capacity, along with a higher cell adhesion rate, and mineralization that is required for tissue engineering. Composites have a better possibility for biomedical and healthcare applications and are used for 2D and 3D scaffold fabrication, drug carrying and delivery, wound healing, tissue regeneration, and engineering. However, the commercialization of these products still needs in-depth research, considering commercial aspects such as stability within ex vivo and in vivo environments, the presence of biological fluids and enzymes, degradation profile, and interaction within living systems. The opportunities and potential applications are diverse, but more elaborative research is needed to address the challenges. In the current article, efforts have been made to summarize the recent advancements in applications of exopolysaccharide composites with natural and synthetic components, with special consideration of pharma and healthcare applications.

Feeding Lactic Acid Bacteria with Different Sugars: Effect on Exopolysaccharides (EPS) Production and Their Molecular Characteristics

Exopolysaccharides (EPS) are complex molecules produced by some microorganisms and used in foods as texturizers and stabilizers, their properties depending on their chemical structure. In this work, three different lactic acid bacteria (LAB), were tested for their ability to produce EPS, by using five different mono- and disaccharides as their sole carbon source. The growth and acidifying ability were analysed, the EPSs were quantified by the official method AOAC 991.43, and their chemical structure was investigated. The amount of EPS varied from 0.71 g/L to 2.38 g/L, and maltose was the best sugar for EPS production by Lacticaseibacillus paracasei 2333. Lacticaseibacillus rhamnosus 1019 produced the highest amount when fed with lactose, whereas the EPS amount of Lactobacillus bulgaricus 1932 was not significantly different depending on the sugar type. The EPS chains consisted of fructose, galactose, glucose, mannose, ribose, glucosamine, galactosamine, and in some cases rhamnose in different proportions, depending on the strain and carbon source. The molecular weight of EPS ranged from <10 KDa to >500 KDa and was again highly dependent on the strain and the sugar used, suggesting the possibility of growing different strains under different conditions to obtain EPS with different potential applications in the food system.

Exopolysaccharide-producing Lacticaseibacillus paracasei strains isolated from kefir as starter for functional dairy products

Exopolysaccharides (EPS) produced by lactic acid bacteria are molecules of great interest for the dairy food industry. Lacticaseibacillus paracasei CIDCA 8339, CIDCA 83123, and CIDCA 83124 are potentially probiotic strains isolated from kefir grains whose EPS-production on MRS broth is dependent on incubation temperature. The aim of the present work is to evaluate the effect of fermentation temperature on the characteristics of EPS produced in milk by L. paracasei strains and the consequent impact on the rheological properties of the fermented products. Additionally, the protective effect of these EPS against Salmonella infection was evaluated in vitro. Acid gels with each strain were obtained by milk fermentation at 20°C, 30°C, and 37°C evidencing for all the strains a reduction in growth and acidification rate at lower temperature. Lacticaseibacillus paracasei CIDCA 83123 showed low fermentation rate at all temperatures requiring between 3 and 8 days to obtain acids gels, whereas CIDCA 8339 and 83124 needed between 24 and 48 h even when the temperature was 20°C. Fermentation temperature led to changes in crude EPS characteristics of the three strains, observing an increase in the relative amount of the high molecular weight fraction when the fermentation temperature diminished. Additionally, EPS₈₃₁₂₄ and EPS₈₃₁₂₃ presented modifications in monosaccharide composition, with a reduction of rhamnose and an increase of amino-sugars as temperature rise. These changes in the structure of EPS₈₃₁₂₄ resulted in an increase of the apparent viscosity of milks fermented at 20°C (223 mPa.s) and 30°C (217 mPa.s) with respect to acid gels obtained at 37°C (167 mPa.s). In order to deepen the knowledge on EPS characteristics, monosaccharide composition of low and high molecular weight EPS fractions were evaluated. Finally, it was evidenced that the preincubation of intestinal epithelial cells Caco-2/TC-7 with EPS₈₃₃₉ and EPS₈₃₁₂₄ partially inhibit the association and invasion of Salmonella. In light of these results, it can be concluded that the selection of the EPS-producing strain along with the appropriate fermentation conditions could be an interesting strategy to improve the technological properties of these L. paracasei fermented milks with potential protective effects against intestinal pathogens.

Effect of fermentation pH on the structure, rheological properties, and antioxidant activities of exopolysaccharides produced by Alteromonas australica QD

The pH value was essential for the growth and metabolism of microorganisms. Acidic pH exopolysaccharide (AC-EPS) and alkaline pH exopolysaccharide (AL-EPS) secreted by A. australica QD mediated by pH were studied in this paper. The total carbohydrate content and molecular weight of AC-EPS (79.59% ± 2.24% (w/w), 8.374 × 10⁵ Da) and AL-EPS (82.48% ± 1.46% (w/w), 6.182 × 10⁵ Da) were estimated and compared. In AC-EPS, mannose (3.78%) and galactose (3.24%) content was more, while the proportion of glucuronic acid was less in comparison to AL-EPS. The scanning electron microscopy revealed the structural differences among the AC-EPS and AL-EPS. Thermogravimetric analysis showed degradation temperatures of 272.8 °C and 244.9 °C for AC-EPS and AL-EPS, respectively. AC-EPS was found to exhibit better rheological properties and emulsifying capabilities, while AL-EPS had superior antioxidant activities. Overall, both AC-EPS and AL-EPS have the potential to be used as emulsifiers and biological antioxidants.

Characterization and Immunological Activity of Exopolysaccharide from Lacticaseibacillus paracasei GL1 Isolated from Tibetan Kefir Grains

Two exopolysaccharide fractions (GL1-E1 and GL1-E2) of Lacticaseibacillus paracasei GL1 were isolated with the molecular weights of 3.9 × 105 Da and 8.2 × 105 Da, respectively. Both fractions possessed mannose, glucose, and galactose in molar ratios of 1.16:1.00:0.1, and 3.81:1.00:0.12, respectively. A structural arrangement of two fractions was proposed by methylation, one-dimensional and two-dimensional nuclear magnetic resonance experiments. The backbone of GL1-E1 consisted of →4)-α-D-Glcp(1→, →3,4)-α-D-Manp(1→, →3,6)-α-D-Manp(1→, →6)-α-D-Manp(1→, and →6)-α-D-Galp(1→ with α-D-Glcp at branching point. The backbone of GL1-E2 consisted of →4)-α-D-Glcp(1→, →3,4)-α-D-Manp(1→, →3,6)-α-D-Manp(1→, →6)-α-D-Manp(1→, →6)-α-D-Galp(1→, and →4)-β-D-Manp(1→, and the side chain also consisted of α-D-Manp residue. In addition, the differential scanning calorimetry (DSC) analysis indicated that both GL1-E1 and GL1-E2 had good thermal stability. Furthermore, the two fractions could promote the viability of RAW264.7 cells and exert an immunomodulatory role by enhancing phagocytosis, increasing nitric oxide (NO) release and promoting the expression of cytokines.

A newly-constructed bifunctional bacterial consortium for removing butyl xanthate and cadmium simultaneously from mineral processing wastewater: Experimental evaluation, degradation and biomineralization

Due to the technological limitations associated with beneficiation technology, large amounts of flotation reagents and heavy metals remain in mineral processing wastewater. Unfortunately, however, no treatment methods are available to mitigate the resulting pollution by them. In this study, a bacterial consortium SDMC (simultaneously degrade butyl xanthate and biomineralize cadmium) was constructed in an effort to simultaneously degrade butyl xanthate (BX) and biomineralize cadmium (Cd) by screening and domesticating two different bacterial species including Hypomicrobium and Sporosarcina. SDMC is efficient in removing the combined pollution due to BX and Cd with a 100% degradation rate for BX and 99% biomineralization rate for Cd within 4 h. Besides, SDMC can tolerate high concentrations of Fe(III) (0-40 mg/L). It has an excellent ability to utilize Fe(III) for enhanced removal of the combined pollutants. SDMC can effectively remove pollutants with a pH range of 6-9. Further, we discussed pathways for potential degradation and biomineralization: Cd(BX)₂-Cd²⁺, BX^-; BX^--CS₂, butyl perxanthate (BPX); Cd²⁺-(Ca0.67,Cd0.33)CO₃. The removal of the combined pollutants primarily entails decomposition, degradation, and biomineralization, C-O bond cleavage, and microbially induced carbonate precipitation (MICP). SDMC is a simple, efficient, and eco-friendly bifunctional bacterial consortium for effective treatment of BX-Cd combined pollution in mineral processing wastewater.

Exopolysaccharides synthesized by lactic acid bacteria: biosynthesis pathway, structure-function relationship, structural modification and applicability

Probiotics and their fermentation products are increasingly been focused on due to their health-boosting effects. Exopolysaccharides (EPS) synthetized by lactic acid bacteria (LAB) are widely applied as texture modifiers in dairy, meat and bakery products owning to their improved properties. Moreover, LAB-derived EPS have been confirmed to possess diverse physiological bioactivities including antioxidant, anti-biofilm, antiviral, immune-regulatory or antitumor. However, the low production and high acquisition cost hinder their development. Even though LAB-derived EPS have been extensively studied for their production-improving, there are only few reports on the systematic elucidation and summary of the relationship among biosynthesis pathway, strain selection, production parameter, structure-function relationship. Therefore, a detailed summary on biosynthesis pathway, production parameter and structure-function relationship of LAB-derived EPS is provided in this review, the structural modifications together with the current and potential applications are also discussed in this paper.

Chicken manure-based bioponics: Effects of acetic acid supplementation on nitrogen and phosphorus recoveries and microbial communities

Bioponics has the potential to recover nutrients from organic waste streams, such as chicken manure and digestate with high volatile fatty acid (VFA) contents through crop production. Acetic acid, a dominant VFA, was supplemented weekly (0, 500, 1000, and 1500 mg/L) in a chicken manure-based bioponic system, and its effect on the performance of bioponics (e.g., plant yield and nitrogen and phosphorus availabilities) was examined. Microbial communities were analyzed using 16S rRNA gene sequencing, and the functional gene abundances were predicted using PICRUSt. Although acetic acid negatively affected plant yield, no significant difference (p > 0.05) was noted in the average nitrogen or phosphorus concentration. In terms of nutrient recovery, the bioponic systems still functioned well, although higher concentrations of acetic acid decreased plant yield and altered the bacterial communities in plant roots and chicken manure sediments. These data suggest that an acetic acid concentration of < 500 mg/L or a longer loading interval is recommended for the effective operation of chicken manure and digestate-based bioponics.