Production of a high molecular weight levan by Bacillus paralicheniformis, an industrially and agriculturally important isolate from the buffalo grass rhizosphere

Efficient Production Strategy of a Novel Postbiotic Produced by Bacillus subtilis and Its Antioxidant and Anti-Inflammatory Effects

Microbially synthesized postbiotics have unique properties and advantages; however, systematic studies on the efficient production and biological functions of postbiotics from Bacillus subtilis are limited, which greatly restricts their applications. In this study, we obtained a novel crude exopolysaccharide (EPS) postbiotic from Bacillus subtilis H4. We systematically optimized the EPS production strategy using single-factor analysis, Plackett-Burman design, the path of steepest ascent method, and response surface methodology. The optimized EPS yield was significantly improved, with a maximum yield of 15.01 g/L under the addition of 4.12% soy peptone, 8.99% sucrose, and 0.06% MnSO4. We found that EPS is a neutral, heterogeneous polysaccharide with a pyranose ring, with a molecular weight of 44,304.913 kDa and a melting point of 218 °C. It consists of glucose, galactose, arabinose, glucosamine, and mannose at a molar ratio of 58.85:19.81:14.75:10.89:6.58. EPS exhibits strong antioxidant capacities, scavenging ABTS and DPPH radicals with IC50 values of 1 and 6 mg/mL, respectively. Moreover, it shows notable anti-inflammatory properties, dramatically inhibiting the lipopolysaccharide (LPS)-induced elevation of nitric oxide (NO) levels and over-activation of the TLR4-NF-κB signaling pathway. These findings highlight the potential of EPS as a multifunctional bioactive compound, offering great promise for its application in the food, clinical, and feed industries.

Structural characteristics, biotechnological production and applications of exopolysaccharides from Bacillus sp.: A comprehensive review

Exopolysaccharides (EPS) produced by Bacillus species display various biological activities and characteristics such as anti-oxidant, immunomodulatory, anti-bacterial, and bioadhesive effects. These attributes confer Bacillus species broad potential applications in diverse fields such as food, medicine, environment, and agriculture. Moreover, Bacillus-derived EPS are easier to produce and yield higher quantities than plant-derived polysaccharides. Despite these advantages, Bacillus-derived EPS still encounter numerous obstacles in industrial production and commercial applications, including elevated costs, the absence of mature fermentation tank production procedures, and the lack of systematic in vivo and in vitro activity and metabolic evaluation. Therefore, it is essential to gain insight into the current status of structure, production, and applications of Bacillus-derived EPS for facilitating their future broader application. This paper provides a comprehensive overview of the current research on the production, separation, characteristics and applications of these related biological products. Furthermore, this paper summarizes the current challenges impeding industrial production of Bacillus-derived EPS, along with potential solutions, and their prospective applications in enhancing the attributes of beneficial biofilms, laying a solid scientific foundation for the applications of Bacillus-derived EPS in industry and agriculture.

Bacillus spp. as microbial factories for levan and fructooligosaccharide production - Recent trends

Levan is a fructan-type homopolysaccharide that has gained increasing attention due to its unique properties and promising applications. It is a fructose-based polymer produced through microbial fermentation by diverse microorganisms, including bacteria, yeasts and archaea. The ongoing research on levan mainly focuses on optimizing production processes, elucidating its biological functions, and uncover novel applications. Studies on novel microbial producer strains and fermentation conditions have led to advancements in production processes. Remarkably, the production of levan using the native producer Bacillus spp. has shown promising trends in yield and molecular weight distribution of levan and levan-type fructooligosaccharides. Ongoing studies on levan highlight the importance of understanding the complexities of levan production for commercial scalability. The present article explores the potential of Bacillus spp. as native levan producers, presenting insights into synthesis mechanisms, factors influencing the production of levan, and genetic modifications aimed at enhancing production efficiency and altering properties.

Enhanced effects of levan hydrogels and bovine grafts on guided bone regeneration: In-vitro and in-vivo analysis

This study was performed to evaluate the regenerative capabilities of levan hydrogels when combined with conventional bone graft materials (Bio-Oss®) in guided bone regeneration (GBR). With the growing interest in the application of levan polysaccharide for regenerative purposes over the last decade, a noticeable gap in in-vivo validations remains. This research therefore fills this gap by utilizing the cytocompatibility and cell proliferation potential of levan hydrogels and marks a preliminary effort in its use in combination with Bio-Oss® for bone regeneration, which was examined both in-vitro and in-vivo for the first time. Considerable increases in cell viability (nearly 180 %) attributed to the addition of levan hydrogels alone and with Bio-Oss® (2:2) was detected. In parallel, a histological examination revealed a significant increase in new bone formation compared with the administration of Bio-Oss® alone. The results conclusively demonstrate for the first time that the combination of levan hydrogel with Bio-Oss® results in histopathologically superior new bone formation compared to Bio-Oss® used alone. Additionally, this combination promoted greater osteoblast density and neovascularization. These outcomes not only emphasize the potential of levan hydrogels in enhancing GBR but also suggest their broader applicability in bone regeneration strategies.

Biopolymer-Levan Characterization in Bacillus Species Isolated from Traditionally Fermented Soybeans (Thua Nao)

Bacterial levans are biopolymers composed of fructose units linked by β-2,6 glycosidic bonds that are degradable, nontoxic and flexible, representing a green technology with significant applications across various industries. Fermented soybeans are a common source of bacteria-producing polysaccharides. In this study, Bacillus siamensis KKSB4, Bacillus velezensis KKSB6 and Bacillus amyloliquefaciens KKSB7 isolated from traditionally fermented soybean (Thua-nao), along with B. velezensis strain 5.18 isolated from Jerusalem artichoke were investigated for their levansucrase activity and subsequent levan production. B. siamensis KKSB4, B. amyloliquefaciens KKSB7 and B. velezensis strain 5.18 exhibited the highest enzyme activity at 30% sucrose, whereas B. velezensis KKSB6 demonstrated optimal activity at 20% sucrose. Characterization of the levans using Fourier transform infrared spectroscopy (FTIR) revealed the peak at 3310.02, 1122.42, 1011.14, and 923.89 cm-1, corresponding to the O-H group in fructose, C-O-H stretching, C-O-C stretching vibrations, and pyranose ring structures, respectively. 13C NMR spectrum of levan aligned with the reference spectrum of B. siamensis, showing proton shifts at H3 (4.19 ppm), H4 (4.10 ppm), H5(3.96 ppm), H6a (3.89 ppm), H1a (3.76 ppm), H1b (3.67 ppm), and H6b (3.56 ppm). All strains produced high molecular weight levans (107-108 Da) with thermal stability, exhibiting melting temperatures exceeding 200 °C. The levans also demonstrated high water and oil holding capacities of over 100%, attributed to their large molecular complexes. Additionally, they exhibited antioxidant activity by scavenging DPPH radicals and oxidizing ABTS, particularly B. siamensis KKSB4 and B. velezensis KKSB6, although low FRAP activity was observed. Furthermore, the levans were produced by B. siamensis KKSB4 and B. velezensis KKSB6 promoted the growth of Streptococcus thermophilus DKT-3, suggesting its potential prebiotic properties. This work highlights B. siamensis KKSB4 and B. velezensis KKSB6 is an outstanding candidate for levan production with diverse functional properties.

In Vitro and In Vivo Interventions Reveal the Health Benefits of Levan-Type Exopolysaccharide Produced by a Fish Gut Isolate Lactobacillus reuteri FW2

Microorganisms synthesize diverse types of exopolysaccharides (EPSs). EPSs with varying structural and physical properties can demonstrate unique health benefits, which allow for their tailored applications as functional foods such as prebiotics. Levan, a fructose-based EPS, is gaining considerable attention as an effective prebiotic to support the growth of beneficial gut bacteria. Consequently, this enhances digestive health, boosts the immune system, and reduces the risk of chronic diseases. Unfortunately, limited studies are available on levan-type EPSs to demonstrate their role as prebiotics. Therefore, in this study, we conducted in vitro and in vivo experiments, concerning intestinal cell integrity and metabolic syndrome, to assess the therapeutic potential of levan derived from Lactobacillus reuteri FW2. The in vitro experimental results revealed that levan improved the survival of impaired HT-29 epithelial cells of the intestine and also exerted antioxidant effects. In the in vivo experiments, mice fed with levan-supplemented feed exhibited low body weight gain, blood glucose, and serum cholesterol levels compared to the control group. These findings highlight the biotherapeutic potential of L. reuteri FW2-derived levan for improving metabolic syndrome and its associated aspects. It also signifies the need for a further detailed investigation based on clinical trials to include levan in dietary supplements for improved health and well-being.

Cell walls, a comparative view of the composition of cell surfaces of plants, algae and microorganisms

While evolutionary studies indicate that the most ancient groups of organisms on Earth likely descended from a common wall-less ancestor, contemporary organisms lacking a carbohydrate-rich cell surface are exceedingly rare. By developing a cell wall to cover the plasma membrane, cells were able to withstand higher osmotic pressures, colonise new habitats and develop complex multicellular structures. This way, the cells of plants, algae and microorganisms are covered by a cell wall, which can generally be defined as a highly complex structure whose main framework is usually composed of carbohydrates. Rather than static structures, they are highly dynamic and serve a multitude of functions that modulate vital cellular processes, such as growth and interactions with neighbouring cells or the surrounding environment. Thus, despite its vital importance for many groups of life, it is striking that there are few comprehensive documents comparing the cell wall composition of these groups. Thus, the aim of this review was to compare the cell walls of plants with those of algae and microorganisms, paying particular attention to their polysaccharide components. It should be highlighted that, despite the important differences in composition, we have also found numerous common aspects and functionalities.

Rhizosphere bacterial exopolysaccharides: composition, biosynthesis, and their potential applications

Bacterial exopolysaccharides (EPS) are biopolymers of carbohydrates, often released from cells into the extracellular environment. Due to their distinctive physicochemical properties, biocompatibility, biodegradability, and non-toxicity, EPS finds applications in various industrial sectors. However, the need for alternative EPS has grown over the past few decades as lactic acid bacteria's (LAB) low-yield EPS is unable to meet the demand. In this case, rhizosphere bacteria with the diverse communities in soil leading to variations in composition and structure, are recognized as a potential source of EPS applicable in various industries. In addition, media components and cultivation conditions have an impact on EPS production, which ultimately affects the quantity, structure, and biological functions of the EPS. Therefore, scientists are currently working on manipulating bacterial EPS by developing cultures and applying abiotic and biotic stresses, so that better production of exopolysaccharides can be attained. This review highlights the composition, biosynthesis, and effects of environmental factors on EPS production along with the potential applications in different fields of industry. Ultimately, an overview of potential future paths and tactics for improving EPS implementation and commercialization is pointed out.

Metabolites of blueberry roots at different developmental stages strongly shape microbial community structure and intra-kingdom interactions at the root-soil interface

The rhizosphere microorganisms of blueberry plants have long coexisted with their hosts under distinctively acidic soil conditions, exerting a profound influence on host performance through mutualistic symbiotic interactions. Meanwhile, plants can regulate rhizosphere microorganisms by exerting host effects to meet the functional requirements of plant growth and development. However, it remains unknown how the developmental stages of blueberry plants affect the structure, function, and interactions of the rhizosphere microbial communities. Here, we examined bacterial communities and root metabolites at three developmental stages (flower and leaf bud development stage, fruit growth and development stage, and fruit maturation stage) of blueberry plants. The results revealed that the Shannon and Chao 1 indices as well as community composition varied significantly across all three developmental stages. The relative abundance of Actinobacteria significantly increased by 10 % (p < 0.05) from stage 1 to stage 2, whereas that of Proteobacteria decreased significantly. The co-occurrence network analysis revealed a relatively complex network with 1179 edges and 365 nodes in the stage 2. Niche breadth was highest at stage 2, while niche overlap tended to increase as the plant developed. Furthermore, the untargeted metabolome analysis revealed that the number of differential metabolites of vitamins, nucleic acids, steroids, and lipids increased between stage 1 to stage2 and stage 2 to stage 3, while those for differential metabolites of carbohydrates and peptides decreased. Significant changes in expression levels of levan, L-glutamic acid, indoleacrylic acid, oleoside 11-methyl ester, threo-syringoylglycerol, gingerglycolipid B, and bovinic acid were highly correlated with the bacterial community structure. Collectively, our study reveals that significant alterations in dominant bacterial taxa are strongly correlated with the dynamics of root metabolites. These findings lay the groundwork for developing prebiotic products to enhance the beneficial effects of root microorganisms and boosting blueberry productivity via a sustainable approach.

Sustainable production of heavy metal-binding levan by a subarctic permafrost thaw lake Pseudomonas strain 2ASCA

Pseudomonas strain 2ASCA isolated in subarctic Québec, Canada, produced a cell membrane bound levan-type exopolymer (yield 1.17 g/L), after incubation in growth media containing 6 % sucrose (w/v) at temperature of 15 °C for 96 h. The objective of this study was to optimize levan production by varying the growth parameters. Moreover, the polymer's chemical characterization has been studied with the aim of increasing knowledge and leading to future applications in many fields, including heavy metal remediation. Higher levan yields (7.37 g/L) were reached by setting up microbial fermentation conditions based on the re-use of the molasses obtained from sugar beet processing. Spectroscopy analyses confirmed the levan-type nature of the exopolymer released by strain 2ASCA, consisting of a β-(2,6)-linked fructose repeating unit. Gel permeation chromatography revealed that the polymer has a molecular weight of 13 MDa. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) showed that the levan sequestered with a strong affinity Cr(III), which has never been previously reported, highlighting an interesting biosorption potential. In addition, SEM analysis revealed the formation of nanoparticles in acidified water solution.

Inulin from halophilic archaeon Haloarcula: Production, chemical characterization, biological, and technological properties

Halophilic archaea are capable of producing fructans, which are fructose-based polysaccharides. However, their biochemical characterization and biological and technological properties have been scarcely studied. The aim of this study was to evaluate the production, chemical characterization, biological and technological properties of a fructan inulin-type biosynthesized by a halophilic archaeon. Fructan extraction was performed through ethanol precipitation and purification by diafiltration. The chemical structure was elucidated using Fourier Transform-Infrared Spectroscopy and Nuclear Magnetic Resonance (NMR). Haloarcula sp. M1 biosynthesizes inulin with an average molecular weight of 8.37 × 106 Da. The maximal production reached 3.9 g of inulin per liter of culture within seven days. The glass transition temperature of inulin was measured at 138.85 °C, and it exhibited an emulsifying index of 36.47 %, which is higher than that of inulin derived from chicory. Inulin from Haloarcula sp. M1 (InuH) demonstrates prebiotic capacity. This study represents the first report on the biological and technological properties of inulin derived from halophilic archaea.

Exopolysaccharides Producing Bacteria: A Review

Bacterial exopolysaccharides (EPS) are essential natural biopolymers used in different areas including biomedicine, food, cosmetic, petroleum, and pharmaceuticals and also in environmental remediation. The interest in them is primarily due to their unique structure and properties such as biocompatibility, biodegradability, higher purity, hydrophilic nature, anti-inflammatory, antioxidant, anti-cancer, antibacterial, and immune-modulating and prebiotic activities. The present review summarizes the current research progress on bacterial EPSs including their properties, biological functions, and promising applications in the various fields of science, industry, medicine, and technology, as well as characteristics and the isolation sources of EPSs-producing bacterial strains. This review provides an overview of the latest advances in the study of such important industrial exopolysaccharides as xanthan, bacterial cellulose, and levan. Finally, current study limitations and future directions are discussed.

Production and characterization of microbial levan using sugarcane (Saccharum spp.) juice and chicken feather peptone as a low-cost alternate medium

An alternate medium consisting of sugarcane juice (SJ) (Saccharum spp.) and chicken feather peptone (CFP) was employed for microbial synthesis of levan. SJ has considerable amounts of vital minerals, vitamins, and amino acids in addition to its major constituent, sucrose. Meanwhile, CFP is also a rich source of essential nutrients such as amino acids, micro and macro elements. Amino acids present in SJ and CFP, such as glutamic acid, arginine, aspartic acid, asparagine and elements such as Ca, Mg favoured the cell growth and levan production. In this present work, levan was produced using Bacillus subtilis MTCC 441 in five different media, namely, sucrose along with defined nutrients (M1), Sugarcane Juice without nutrients (M2), SJ with defined nutrients (M3), SJ along with chicken feather peptone (M4) and sucrose without nutrient (M5). Alternative nutrient medium using SJ and CFP (M4) showed a promising levan yield of 0.32 ± 0.01 g of levan/g of sucrose consumed, which is 64% of the theoretical levan yield possible. Levan produced was characterized using Nuclear Magnetic Resonance (NMR) and Gel Permeation Chromatography (GPC). There is a change in low molecular weight fractions of levan obtained from SJ and CFP medium compared to the defined medium. Produced levan from the composite medium exhibited strong antioxidant activity and was biocompatible when tested against endothelial cells. The substrate cost was 20% lower than the cost of defined medium. Thus, a composite medium made of SJ and CFP can serve as an alternate low-cost medium for microbial fermentation.