A Novel EPS-Producing Strain of Bacillus licheniformis Isolated from a Shallow Vent Off Panarea Island (Italy)

Exopolysaccharide production by salt-tolerant bacteria: Recent advances, current challenges, and future prospects

Natural biopolymers derived from exopolysaccharides (EPSs) are considered eco-friendly and sustainable alternatives to available traditional synthetic counterparts. Salt-tolerant bacteria inhabiting harsh ecological niches have evolved a number of unique adaptation strategies allowing them to maintain cellular integrity and assuring their long-term survival; among these, producing EPSs can be adopted as an effective strategy to thrive under high-salt conditions. A great diversity of EPSs from salt-tolerant bacteria have attracted widespread attention recently. Because of factors such as their unique structural, physicochemical, and functional characteristics, EPSs are commercially valuable for the global market and their application potential in various sectors is promising. However, large-scale production and industrial development of these biopolymers are hindered by their low yields and high costs. Consequently, the research progress and future prospects of salt-tolerant bacterial EPSs must be systematically reviewed to further promote their application and commercialization. In this review, the structure and properties of EPSs produced by a variety of salt-tolerant bacterial strains isolated from different sources are summarized. Further, feasible strategies for solving production bottlenecks are discussed, which provides a scientific basis and direct reference for more scientific and rational EPS development.

Production of exopolysaccharides from Bacillus licheniformis, a thermophilic bacteria from hot spring of Jharkhand

Thermophiles are the microorganisms which thrive under extreme conditions such as high temperature, making them significant for scientific interest. This study provides information based on isolation of thermophilic strain from Surajkund and Ramkund, hot spring of Jharkhand at 50, 60 and 70 °C. Two of the best isolates were used for the extraction of exopolysaccharides. Additionally, the lyophilized product obtained was further analyzed for protein and total sugar estimation. The FTIR analysis revealed the presence of different functional groups such as hydroxyl, C-H stretching, vibration of aliphatic CH2 and glycosidic linkage, thus proving the product obtained from bacteria was an exopolysaccharides The FESEM analysis of exopolysaccharides show varying surface morphology that is from porous to globular structure. Based on 16S rRNA sequences, the isolates from Surajkund (ON795919) and Ramkund (ON795916) were different strains of Bacillus licheniformis. This is the first report on exopolysaccharide secreting thermophilic strain from these hot springs.

Exopolysaccharides produced by Bacillus spp. inhibit biofilm formation by Staphylococcus aureus strains associated with bovine mastitis

Bovine mastitis is a costly disease in the dairy sector worldwide. Here the objective was to identify and characterize anti-biofilm compounds produced by Bacillus spp. against S. aureus associated with bovine mastitis. Results showed that cell-free supernatants of three Bacillus strains (out of 33 analysed) reduced S. aureus biofilm formation by approximately 40 % without affecting bacterial growth. The anti-biofilm activity was associated with exopolysaccharides (EPS) secreted by Bacillus spp. The EPS decreased S. aureus biofilm formation in a dose-dependent manner, inhibiting biofilm formation by 83 % at 1 mg/mL. The EPS also showed some biofilm disruption activity (up to 36.4 %), which may be partially mediated by increased expression of the aur gene. The characterization of EPS produced by Bacillus velezensis 87 and B. velezensis TR47II revealed macromolecules with molecular weights of 31.2 and 33.7 kDa, respectively. These macromolecules were composed mainly of glucose (mean = 218.5 μg/mg) and mannose (mean = 241.5 μg/mg) and had similar functional groups (pyranose ring, beta-type glycosidic linkage, and alkynes) as revealed by FT-IR. In conclusion, this study shows the potential applications of EPS produced by B. velezensis as an anti-biofilm compound that could contribute to the treatment of bovine mastitis caused by S. aureus.

Exploring Extremophiles from Bulgaria: Biodiversity, Biopolymer Synthesis, Functional Properties, Applications

Bulgaria stands out as a country rich in diverse extreme environments, boasting a remarkable abundance of mineral hot waters, which positions it as the second-largest source of such natural resources in Europe. Notably, several thermal and coastal solar salterns within its territory serve as thriving habitats for thermophilic and halophilic microorganisms, which offer promising bioactive compounds, including exopolysaccharides (EPSs). Multiple thermophilic EPS producers were isolated, along with a selection from several saltern environments, revealing an impressive taxonomic and bacterial diversity. Four isolates from three different thermophilic species, Geobacillus tepidamans V264, Aeribacillus pallidus 418, Brevibacillus thermoruber 423, and Brevibacillus thermoruber 438, along with the halophilic strain Chromohalobacter canadensis 28, emerged as promising candidates for further exploration. Optimization of cultivation media and conditions was conducted for each EPS producer. Additionally, investigations into the influence of aeration and stirring in laboratory bioreactors provided valuable insights into growth dynamics and polymer synthesis. The synthesized biopolymers showed excellent emulsifying properties, emulsion stability, and synergistic interaction with other hydrocolloids. Demonstrated biological activities and functional properties pave the way for potential future applications in diverse fields, with particular emphasis on cosmetics and medicine. The remarkable versatility and efficacy of biopolymers offer opportunities for innovation and development in different industrial sectors.

Marine versus Non-Marine Bacterial Exopolysaccharides and Their Skincare Applications

Bacteria are well-known to synthesize high molecular weight polysaccharides excreted in extracellular domain, which constitute their protective microenvironment. Several bacterial exopolysaccharides (EPS) are commercially available for skincare applications in cosmetic products due to their unique structural features, conferring valuable biological and/or textural properties. This review aims to give an overview of bacterial EPS, an important group of macromolecules used in cosmetics as actives and functional ingredients. For this purpose, the main chemical characteristics of EPS are firstly described, followed by the basics of the development of cosmetic ingredients. Then, a focus on EPS production, including upstream and downstream processes, is provided. The diversity of EPS used in the cosmetic industry, and more specifically of marine-derived EPS is highlighted. Marine bacteria isolated from extreme environments are known to produce EPS. However, their production processes are highly challenging due to high or low temperatures; yield must be improved to reach economically viable ingredients. The biological properties of marine-derived EPS are then reviewed, resulting in the highlight of the challenges in this field.

Marine Microbial Polysaccharides: An Untapped Resource for Biotechnological Applications

As the largest habitat on Earth, the marine environment harbors various microorganisms of biotechnological potential. Indeed, microbial compounds, especially polysaccharides from marine species, have been attracting much attention for their applications within the medical, pharmaceutical, food, and other industries, with such interest largely stemming from the extensive structural and functional diversity displayed by these natural polymers. At the same time, the extreme conditions within the aquatic ecosystem (e.g., temperature, pH, salinity) may not only induce microorganisms to develop a unique metabolism but may also increase the likelihood of isolating novel polysaccharides with previously unreported characteristics. However, despite their potential, only a few microbial polysaccharides have actually reached the market, with even fewer being of marine origin. Through a synthesis of relevant literature, this review seeks to provide an overview of marine microbial polysaccharides, including their unique characteristics. In particular, their suitability for specific biotechnological applications and recent progress made will be highlighted before discussing the challenges that currently limit their study as well as their potential for wider applications. It is expected that this review will help to guide future research in the field of microbial polysaccharides, especially those of marine origin.

Exopolysaccharide Production from Marine-Derived Brevundimonas huaxiensis Obtained from Estremadura Spur Pockmarks Sediments Revealing Potential for Circular Economy

Marine environments represent an enormous biodiversity reservoir due to their numerous different habitats, being abundant in microorganisms capable of producing biomolecules, namely exopolysaccharides (EPS), with unique physical characteristics and applications in a broad range of industrial sectors. From a total of 67 marine-derived bacteria obtained from marine sediments collected at depths of 200 to 350 m from the Estremadura Spur pockmarks field, off the coast of Continental Portugal, the Brevundimonas huaxiensis strain SPUR-41 was selected to be cultivated in a bioreactor with saline culture media and glucose as a carbon source. The bacterium exhibited the capacity to produce 1.83 g/L of EPS under saline conditions. SPUR-41 EPS was a heteropolysaccharide composed of mannose (62.55% mol), glucose (9.19% mol), rhamnose (19.41% mol), glucuronic acid (4.43% mol), galactose (2.53% mol), and galacturonic acid (1.89% mol). Moreover, SPUR-41 EPS also revealed acyl groups in its composition, namely acetyl, succinyl, and pyruvyl. This study revealed the importance of research on marine environments for the discovery of bacteria that produce new value-added biopolymers for pharmaceutical and other biotechnological applications, enabling us to potentially address saline effluent pollution via a sustainable circular economy.

Anti-Bacterial Adhesion on Abiotic and Biotic Surfaces of the Exopolysaccharide from the Marine Bacillus licheniformis B3-15

The eradication of bacterial biofilm represents a crucial strategy to prevent a clinical problem associated with microbial persistent infection. In this study we evaluated the ability of the exopolysaccharide (EPS) B3-15, produced by the marine Bacillus licheniformis B3-15, to prevent the adhesion and biofilm formation of Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 on polystyrene and polyvinyl chloride surfaces. The EPS was added at different times (0, 2, 4 and 8 h), corresponding to the initial, reversible and irreversible attachment, and after the biofilm development (24 or 48 h). The EPS (300 µg/mL) impaired the initial phase, preventing bacterial adhesion even when added after 2 h of incubation, but had no effects on mature biofilms. Without exerting any antibiotic activity, the antibiofilm mechanisms of the EPS were related to the modification of the (i) abiotic surface properties, (ii) cell-surface charges and hydrophobicity, and iii) cell-to-cell aggregation. The addition of EPS downregulated the expression of genes (lecA and pslA of P. aeruginosa and clfA of S. aureus) involved in the bacterial adhesion. Moreover, the EPS reduced the adhesion of P. aeruginosa (five logs-scale) and S. aureus (one log) on human nasal epithelial cells. The EPS could represent a promising tool for the prevention of biofilm-related infections.

Production and Characterisation of an Exopolysaccharide by Bacillus amyloliquefaciens: Biotechnological Applications

The Bacillus amyloliquefaciens RT7 strain was isolated from an extreme acidic environment and identified. The biodegradation capabilities of the strain using different carbon sources (glucose, oleic acid, Tween 80, PEG 200, and the combination of glucose-Tween 80) were evaluated via an indirect impedance technique. The glucose-Tween 80 combination was further studied using nuclear magnetic resonance (NMR). The exopolysaccharide (EPS_RT7) that had been produced with the strain when biodegrading glucose-Tween 80 was isolated and characterised using different techniques (GC-MS, HPLC/MSMS, ATR-FTIR, TGA, and DSC), and its molecular weight was estimated. The results show that the average molecular weight of EPS_RT7 was approximately 7.0794 × 10⁴ Da and a heteropolysaccharide composed of mannose, glucose, galactose, and xylose (molar ratio, 1:0.5:0.1:0.1) with good thermostability. EPS_RT7 showed good emulsifying activity against different natural oils and hydrocarbons at high concentrations (2 mg/mL) and at the studied pH range (3.1-7.2). It also presented good emulsifying activity compared to that of commercial emulsifiers. Lastly, EPS_RT7 showed antioxidant capacity for different free radicals, a lack of cytotoxicity, and antioxidant activity at the cellular level. EPS_RT7 has promising applications in bioremediation processes and other industrial applications.

Biological properties of exopolysaccharides produced by Bacillus spp

There is currently a constant search for ecofriendly bioproducts, which could contribute to various biomedical applications. Among bioproducts, exopolysaccharides are prominent contemporary extracellular biopolymers that are produced by a great variety of bacterial species. These homo- or heteropolymers are composed of monomeric sugar units linked by glycosidic bonds, which are secreted to the external medium. Bacillus spp. are reported to be present in different ecosystems and produce exopolysaccharides with different biological properties such as antioxidant, antibacterial, antiviral anti-inflammatory, among others. Since a great diversity of bacterial strains are able to produce exopolysaccharides, a great variation in the molecular composition is observed, which is indeed present in some of the chemical structures predicted until date. These molecular characteristics and their relations with different biological functions are discussed in order to visualize future applications in biomedical section.

Hydrating Capabilities of the Biopolymers Produced by the Marine Thermophilic Bacillus horneckiae SBP3 as Evaluated by ATR-FTIR Spectroscopy

The surfactin-like lipopeptide (BS-SBP3) and the exopolysaccharide (EPS-SBP3) produced by the polyextremophilic Bacillus horneckiae SBP3 (DSM 103063) have been recently described as valuable biopolymers useful in biotechnological applications. To investigate the hydrating capabilities of BS-SBP3 and EPS-SBP3, here we evaluated (i) their wetting properties, measuring the contact angle; (ii) their moisture uptake abilities using the gravimetric method; and (iii) their hydrating states (from 0 to 160% w/w of water content) using ATR-FTIR spectroscopy. BS-SBP3 reduced the water contact angle on a hydrophobic surface from 81.7° to 51.3°, whereas the contact angle in the presence of EPS-SBP3 was 72.9°, indicating that BS-SBP3 improved the wettability of the hydrophobic surface. In the moisture uptake tests, EPS-SBP3 absorbed more water than BS-SBP3, increasing its weight from 10 mg to 30.1 mg after 36 h of 100% humidity exposure. Spectral distance and cross-correlation analyses were used to evaluate the molecular changes of the two biopolymers during the hydration process. As the water concentration increased, BS-SBP3 spectra changed in intensity in the two contributions of the OH-stretching band named "closed" and "open" (3247 and 3336 cm^-1, respectively). Differently, the spectra of EPS-SBP3 exhibited a broader peak (3257 cm^-1), which shifted at higher water concentrations. As evaluated by the spectral distance and the wavelet cross-correlation analysis, the OH-stretching bands of the BS-SBP3 and EPS-SBP3 changed as a function of water content, with two different sigmoidal trends having the inflection points at 80% and 48%, respectively, indicating peculiar water-properties of each biopolymer. As wetting agents, these biopolymers might replace industrially manufactured additives in agriculture and the food and cosmetic industries.

Extracellular Polymeric Substances: Still Promising Antivirals

Sulfated polysaccharides and other polyanions have been promising candidates in antiviral research for decades. These substances gained attention as antivirals when they demonstrated a high inhibitory effect in vitro against human immunodeficiency virus (HIV) and other enveloped viruses. However, that initial interest was followed by wide skepticism when in vivo assays refuted the initial results. In this paper we review the use of sulfated polysaccharides, and other polyanions, in antiviral therapy, focusing on extracellular polymeric substances (EPSs). We maintain that, in spite of those early difficulties, the use of polyanions and, specifically, the use of EPSs, in antiviral therapy should be reconsidered. We base our claim in several points. First, early studies showed that the main disadvantage of sulfated polysaccharides and polyanions is their low bioavailability, but this difficulty can be overcome by the use of adequate administration strategies, such as nebulization of aerosols to gain access to respiratory airways. Second, several sulfated polysaccharides and EPSs have demonstrated to be non-toxic in animals. Finally, these macromolecules are non-specific and therefore they might be used against different variants or even different viruses.

Optimization and Characterization of a Novel Exopolysaccharide from Bacillus haynesii CamB6 for Food Applications

Extremophilic microorganisms often produce novel bioactive compounds to survive under harsh environmental conditions. Exopolysaccharides (EPSs), a constitutive part of bacterial biofilm, are functional biopolymers that act as a protecting sheath to the extremophilic bacteria and are of high industrial value. In this study, we elucidate a new EPS produced by thermophilic Bacillus haynesii CamB6 from a slightly acidic (pH 5.82) Campanario hot spring (56.4 °C) located in the Central Andean Mountains of Chile. Physicochemical properties of the EPS were characterized by different techniques: Scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS), Atomic Force Microscopy (AFM), High-Performance Liquid Chromatography (HPLC), Gel permeation chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), 1D and 2D Nuclear Magnetic Resonance (NMR), and Thermogravimetric analysis (TGA). The EPS demonstrated amorphous surface roughness composed of evenly distributed macromolecular lumps. GPC and HPLC analysis showed that the EPS is a low molecular weight heteropolymer composed of mannose (66%), glucose (20%), and galactose (14%). FTIR analysis demonstrated the polysaccharide nature (–OH groups, Acetyl groups, and pyranosic ring structure) and the presence of different glycosidic linkages among sugar residues, which was further confirmed by NMR spectroscopic analyses. Moreover, D-mannose α-(1→2) and α-(1→4) linkages prevail in the CamB6 EPS structure. TGA revealed the high thermal stability (240 °C) of the polysaccharide. The functional properties of the EPS were evaluated for food industry applications, specifically as an antioxidant and for its emulsification, water-holding (WHC), oil-holding (OHC), and flocculation capacities. The results suggest that the study EPS can be a useful additive for the food-processing industry.

Fucose-containing bacterial exopolysaccharides: Sources, biological activities, and food applications

Bacterial exopolysaccharides are high molecular weight polysaccharides that are secreted by a wide range of bacteria, with diverse structures and easy preparation. Fucose, fucose-containing oligosaccharides (FCOs), and fucose-containing polysaccharides (FCPs) have important applications in the food and medicine fields, including applications in products for removing Helicobacter pylori and infant formula powder. Fucose-containing bacterial exopolysaccharide (FcEPS) is a prospective source of fucose, FCOs, and FCPs. This review systematically summarizes the common sources and applications of FCPs and FCOs and the bacterial strains capable of producing FcEPS reported in recent years. The repeated-unit structures, synthesis pathways, and factors affecting the production of FcEPS are reviewed, as well as the degradation methods of FcEPS for preparing FCOs. Finally, the bioactivities of FcEPS, including anti-oxidant, prebiotic, anti-cancer, anti-inflammatory, anti-viral, and anti-microbial activities, are discussed and may serve as a reference strategy for further applications of FcEPS in the functional food and medicine industries.

Ecological and Biotechnological Relevance of Mediterranean Hydrothermal Vent Systems

Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the living organisms, which have to develop adaptation strategies to survive. Hydrothermal systems have attracted the interest of researchers due to their enormous ecological and biotechnological relevance. From ecological perspective, these acidified habitats are useful natural laboratories to predict the effects of global environmental changes, such as ocean acidification at ecosystem level, through the observation of the marine organism responses to environmental extremes. In addition, hydrothermal vents are known as optimal sources for isolation of thermophilic and hyperthermophilic microbes, with biotechnological potential. This double aspect is the focus of this review, which aims at providing a picture of the ecological features of the main Mediterranean hydrothermal vents. The physiological responses, abundance, and distribution of biotic components are elucidated, by focusing on the necto-benthic fauna and prokaryotic communities recognized to possess pivotal role in the marine ecosystem dynamics and as indicator species. The scientific interest in hydrothermal vents will be also reviewed by pointing out their relevance as source of bioactive molecules.

Production of Exopolysaccharides by Cultivation of Halotolerant Bacillus atrophaeus BU4 in Glucose- and Xylose-Based Synthetic Media and in Hydrolysates of Quinoa Stalks

A halotolerant, exopolysaccharide-producing bacterium isolated from the Salar de Uyuni salt flat in Bolivia was identified as Bacillus atrophaeus using next-generation sequencing. Comparisons indicate that the genome most likely (p-value: 0.0024) belongs to a subspecies previously not represented in the database. The growth of the bacterial strain and its ability to produce exopolysaccharides (EPS) in synthetic media with glucose or xylose as carbon sources, and in hydrolysates of quinoa stalks, was investigated. The strain grew well in all synthetic media, but the growth in glucose was better than that in xylose. Sugar consumption was better when initial concentrations were low. The growth was good in enzymatically produced cellulosic hydrolysates but was inhibited in hemicellulosic hydrolysates produced using hydrothermal pretreatment. The EPS yields were up to 0.064 g/g on initial glucose and 0.047 g/g on initial xylose, and was higher in media with relatively low sugar concentrations. The EPS was isolated and purified by a sequential procedure including centrifugation, cold ethanol precipitation, trichloroacetic acid treatment, dialysis, and freeze-drying. Glucose and mannose were the main sugars identified in hydrolyzed EPS. The EPS was characterized by size-exclusion chromatography, Fourier-transform infrared (FTIR) spectroscopy, heteronuclear single-quantum coherence nuclear magnetic resonance (HSQC NMR) spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. No major differences were elucidated between EPS resulting from cultivations in glucose- or-xylose-based synthetic media, while some divergences with regard to molecular-weight averages and FTIR and HSQC NMR spectra were detected for EPS from hydrolysate-based media.

Performance Evaluation of Bio-Based Fractions Derived from Bacillus spp. for Potential In Situ Soil Stabilisation

Current and future research focuses on the use of renewable technologies and materials to stabilise weak soils, of varying degrees, for road construction applications. Soil stabilisation is a method of strengthening a natural soil to meet this purpose. Our interest is in the use of bio-based components, derived from microbial growth processes, that contribute to the needed desirable strength characteristics for in situ soil stabilisation. This investigation focuses on novel Bacillus-based stabilisers obtained from the vegetative and spore growth stage. In this study, eighteen bio-based components were derived from a Bacillus licheniformis fermentation and extracted into various aqueous and non-aqueous fractions for strength property assessment. The strength properties of the treated soils (i.e., dolerite and weathered granite soil) were assessed via previously developed lab-scale equipment to rapidly pre-select the best performing fractions, (i.e., compression stress, erosion, abrasion, and water absorption tests). The effect of one superior performing prototype (a) was validated at large-scale, using standard erosion and abrasion tests (i.e., whole broth at 1.8% stabiliser concentrations), and showed resistance to abrasion (3.37 ± 0.03%) (p value ≤ 0.0001) and resistance to erosion (33.20 ± 0.15%) (p value ≤ 0.001). The elemental composition and microstructure of the bio-stabilised soil was determined using energy dispersive X-ray spectroscopy and scanning electron microscopy, respectively. This evaluation formed part of the selection of the best performing Bacillus derived fractions and achieved a proof of concept for the next phase of product prototype development. This study demonstrated a novel bio-mediated approach to the overall criteria for evaluation and selection of candidate product prototype/s, for stabilisation of two varying soils, and for potential application in road construction works.

Extraction and characterization of an exopolysaccharide from a marine bacterium

The marine bacterial exopolysaccharides (EPS) have transfigured the biotech sector with their myriad applications and prospects. This work was carried out to characterize and analyze the functional and biochemical properties of an EPS (EPS-DR3A) produced by a marine bacterium, Pseudoalteromonas sp. YU16-DR3A. The bacterium was cultured in Zobell marine broth for the production of EPS. The extracted EPS designated as EPS-DR3A was composed of 69% carbohydrates and 7.6% proteins with a molecular weight of 20 kDa. FT-IR spectra showed the presence of different functional groups. The monosaccharide analysis performed using GC-MS showed the presence of fucose, erythrotetrose, ribose, and glucose as monomers. EPS-DR3A showed excellent emulsifying activity against the tested hydrocarbons and food oils with stable emulsions. Rheological analysis of EPS-DR3A revealed the pseudoplastic behavior. The EPS-DR3A displayed good thermal stability with a degradation temperature of 249 °C and a melting point at 322 °C. Further, it had the ability to scavenge DPPH and nitric oxide free radicals with good total antioxidant activity. The in vitro biocompatibility study of EPS-DR3A showed high degree of biocompatibility with human dermal fibroblast cells at the tested concentrations. Taken together, the findings such as thermostability, emulsifying activity, pseudoplasticity, antioxidant activity, and biocompatibility of EPS-DR3A make this biomolecule an important candidate for a wide range of biomedical applications.

New Exopolysaccharides Produced by Bacillus licheniformis 24 Display Substrate-Dependent Content and Antioxidant Activity

Bacillus licheniformis is a soil bacterium with many industrial applications. In addition to enzymes, platform chemicals, antibiotics and phytohormones, the species produces exopolysaccharides (EPSs) of various biological activities. This study revealed that Bulgarian isolate B. licheniformis 24 produced EPSs consisting of galactose, glucose and mannose with substrate-dependent ratio. From glucose, B. licheniformis 24 secreted EPS1, consisting of 54% galactose, 39% glucose and 7% mannose. From fructose, the strain formed EPS2, containing 51% glucose, 30% mannose and 19% galactose. Batch cultivation in flasks yielded 2.2–2.6 g/L EPS1 and 1.90–2.11 g/L EPS2. Four to five times higher yields of EPS were obtained from both substrates during batch and fed-batch processes in a fermenter at 37.8 °C, pH 6.2 and aeration 3.68 vvm. The batch process with 200 g/L of starting substrates received 9.64 g/L EPS1 and 6.29 g/L EPS2, reaching maximum values at the 33rd and 24th h, respectively. Fed-batch fermentation resulted in the highest yields, 12.61 g/L EPS1 and 7.03 g/L EPS2. In all processes, EPSs were produced only in the exponential growth phase. Both EPSs exhibited antioxidant activity, but EPS2 was much more potent in this regard, reaching 811 μM Vitamin C Equivalent Antioxidant Capacity (versus 135 μM for EPS1). EPS1 displayed antibacterial activity against a non-O1 strain of Vibrio cholerae.

Box-Wilson Design for Optimization of in vitro Levan Production and Levan Application as Antioxidant and Antibacterial Agents

Background:

Methods:

Results:

Conclusion:

Box-Wilson Design for Optimization of in vitro Levan Production and Levan Application as Antioxidant and Antibacterial Agents

Background

Levan or fructan, a polysaccharide of fructose, is widely used in various commercial industries. Levan could be produced by many organisms, including plants and bacteria. The cloning of the gene from Bacillus licheniformis, which expressed levansucrase in Escherichia coli host, was carried out successfully. In the present study, we performed the in vitro production of levan and analyzed its potential application as antibacterial and antioxidant agents.

Methods

In vitro levan production catalyzed by heterologous-expressed levansucrase Lsbl-bk1 and Lsbl-bk2 was optimized with Box-Wilson design. The antibacterial activity of the produced levan was carried out using agar well diffusion method, while its antioxidant activity was tested by free radical scavenging assays.

Results

The optimum conditions for levan production were observed at 36 °C and pH 7 in 12% (w/v) sucrose for levansucrase Lsbl-bk1, while the optimum catalysis of levansucrase Lsbl-bk2 was obtained at 32 oC and pH 8 in the same sucrose concentration. The in vitro synthesized levan showed an antibacterial activity within a concentration range of 10-20% (w/v) against Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa. The same levan was also able to inhibit the 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity with the antioxidant strength of 75% compared to ascorbic acid inhibition.

Conclusion

Our study, therefore, shows that the optimized heterologous expression of levansucrases encoded by Lsbl-bk1 and Lsbl-bk2 could open the way for industrial levan production as an antibacterial and antioxidant agent.

Exopolysaccharide of Anoxybacillus pushchinoensis G11 has antitumor and antibiofilm activities

Exopolysaccharides (EPS/EPSs) possess several various applications in the food and pharmaceutical industries. This study was performed to investigate the biological (antibiofilm and antitumor), rheological (temperature, shear rate, and density) and chemical (solubility, carbohydrate and protein content, composition, molecular weight, functional group analysis, thermal analysis, X-ray diffraction pattern and scanning electron microscopy) properties of the EPS, which was purified from the locally isolated thermophilic bacterium Anoxybacillus pushchinoensis G11 (MN720646). EPS was found to have antibiofilm and antitumor [lung (A-549) and colon (Caco-2 and HT-29) cancer] activities. The viscosity of EPS showing Newtonian flow was temperature dependent. As chemical properties, the EPS was found to be a heteropolysaccharide containing arabinose (57%), fructose (26%), glucose (12%), and galactose (5%). EPS contained 93% carbohydrates and 1.08% protein. The molecular weight of EPS was determined as 75.5 kDa. The FTIR analysis confirmed the presence of sulfate ester (band at 1217 cm^-1), an indication of the antitumor effect. The EPS was semi-crystalline. It could maintain 36% of its weight at 800 °C and crystallization and melting temperatures were 221 and 255.6 °C. This is the first report on the EPS production potential and the biological activity of A. pushchinoensis.

A review of extracellular polysaccharides from extreme niches: An emerging natural source for the biotechnology. From the adverse to diverse!

Every year, new organisms that survive and colonize adverse environments are discovered and isolated. Those organisms, called extremophiles, are distributed throughout the world, both in aquatic and terrestrial environments, such as sulfurous marsh waters, hydrothermal springs, deep waters, volcanos, terrestrial hot springs, marine saltern, salt lakes, among others. According to the ecosystem inhabiting, extremophiles are categorized as thermophiles, psychrophiles, halophiles, acidophiles, alkalophilic, piezophiles, saccharophiles, metallophiles and polyextremophiles. They have developed chemical adaptation strategies that allow them to maintain their cellular integrity, altering physiology or improving repair capabilities; one of them is the biosynthesis of extracellular polysaccharides (EPS), which constitute a slime and hydrated matrix that keep the cells embedded, protecting from environmental stress (desiccation, salinity, temperature, radiation). EPS have gained interest; they are explored by their unique properties such as structural complexity, biodegradability, biological activities, and biocompatibility. Here, we present a review concerning the biosynthesis, characterization, and potential EPS applications produced by extremophile microorganisms, namely, thermophiles, halophiles, and psychrophiles. A bibliometric analysis was conducted, considering research articles published within the last two decades. Besides, an overview of the culture conditions used for extremophiles, the main properties and multiple potential applications of their EPS is also presented.

Genomic insights into waste valorized extracellular polymeric substances (EPS) produced by Bacillus sp. ISTL8

The present study discusses the genomic analysis of Bacillus sp. ISTL8 along with the production of EPS (Extracellular polymeric substances) using carbofuran, a toxic carbamate pesticide. Bacillus strain was isolated from landfill soil and evaluated for high growth rates and EPS production. One strain, renamed ISTL8 grew on a broad range of carbon sources, including toxic carbofuran, while producing copious EPS. Growth assays verified the strain to be thermophilic, low salt tolerant, and with a preference for neutral pH. SEM (Scanning Electron Microscopy) was used for morphological characterization of the EPS while the monomeric composition, bonding patterns and functional groups were deduced by GC-MS (Gas Chromatography-Mass Spectrometry), ¹H and ¹³C NMR (Nuclear Magnetic Resonance) and FTIR (Fourier Transform Infrared Spectroscopy). The production of EPS using carbofuran (carbamate pesticide) as a carbon source was found to be 6.20 ± 0.29 g L^-1 containing 61.17% w/w carbohydrates, 29.72% w/w proteins and 6.11% w/w lipids (of dry EPS). The potential cytotoxicity of EPS was evaluated with 3- (4,5-dimethyl thiazol-2-Yl) -2,5-diphenyl tetrazolium bromide (MTT) assay and found non-toxic (2.25%). WGS (Whole genome sequencing) was performed for the strain Bacillus sp. ISTL8 producing EPS; an array of genes putatively involved in the EPS production were identified in several different genomic locations, guiding potential genetic manipulation studies in the future. The results highlight the potency of a bacterial isolate Bacillus sp. ISTL8 to produce non-cytotoxic EPS using carbofuran that can be further harnessed for environmental and commercial applications. Additionally, WGS revealed an array of EPS specific genes which can be effectively engineered for much enhanced production.

Effects of Heavy Ion Particle Irradiation on Spore Germination of Bacillus spp. from Extremely Hot and Cold Environments

Extremophiles are optimal models in experimentally addressing questions about the effects of cosmic radiation on biological systems. The resistance to high charge energy (HZE) particles, and helium (He) ions and iron (Fe) ions (LET at 2.2 and 200 keV/µm, respectively, until 1000 Gy), of spores from two thermophiles, Bacillushorneckiae SBP3 and Bacilluslicheniformis T14, and two psychrotolerants, Bacillus sp. A34 and A43, was investigated. Spores survived He irradiation better, whereas they were more sensitive to Fe irradiation (until 500 Gy), with spores from thermophiles being more resistant to irradiations than psychrotolerants. The survived spores showed different germination kinetics, depending on the type/dose of irradiation and the germinant used. After exposure to He 1000 Gy, D-glucose increased the lag time of thermophilic spores and induced germination of psychrotolerants, whereas L-alanine and L-valine increased the germination efficiency, except alanine for A43. FTIR spectra showed important modifications to the structural components of spores after Fe irradiation at 250 Gy, which could explain the block in spore germination, whereas minor changes were observed after He radiation that could be related to the increased permeability of the inner membranes and alterations of receptor complex structures. Our results give new insights on HZE resistance of extremophiles that are useful in different contexts, including astrobiology.

Peculiarities of extracellular polymeric substances produced by Antarctic bacteria and their possible applications

Extracellular polymeric substances (EPSs) possess diversified ecological role, including the cell adhesion to surfaces and cell protection, and are highly involved in the interactions between the bacterial cells and the bulk environments. Interestingly, EPSs find valuable applications in the industrial field, due to their chemical versatility. In this context, Antarctic bacteria have not been given the attention they deserve as producers of EPS molecules and a very limited insight into their EPS production capabilities and biotechnological potential is available in literature to date. Antarctic EPS-producing bacteria are mainly psychrophiles deriving from the marine environments (generally sea ice and seawater) around the continent, whereas a unique thermophilic bacterium, namely Parageobacillus thermantarcticus strain M1, was isolated from geothermal soil of the crater of Mount Melbourne. This mini-review is aimed at showcasing the current knowledge on EPS-producing Antarctic bacteria and the chemical peculiarities of produced EPSs, highlighting their biotechnological potential and the yet unexplored treasure they represent for biodiscovery.

Marine Bacterial Exopolymers-Mediated Green Synthesis of Noble Metal Nanoparticles with Antimicrobial Properties

A straightforward and green method for the synthesis of gold, silver, and silver chloride nanoparticles (Au NPs and Ag/AgCl NPs) was developed using three different microbial exopolymers (EP) as reducing and stabilizing agents. The exopolysaccharides EPS B3-15 and EPS T14 and the poly-γ-glutamic acid γ-PGA-APA were produced by thermophilic bacteria isolated from shallow hydrothermal vents off the Eolian Islands (Italy) in the Mediterranean Sea. The production of metal NPs was monitored by UV-Vis measurements by the typical plasmon resonance absorption peak and their antimicrobial activity towards Gram-positive and Gram- negative bacteria (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa), as well as fungi (Candida albicans) was investigated. The biological evaluation showed no activity for EP-Au NPs, except against E. coli, whereas EP-Ag NPs exhibited a broad-spectrum of activity. The chemical composition, morphology, and size of EP-Ag NPs were investigated by UV-Vis, zeta potential (ζ), dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM). The best antimicrobial results were obtained for EPS B3-15-Ag NPs and EPS T14-Ag NPs (Minimum Inhibitory Concentration, MIC: 9.37-45 µg/mL; Minimum Bactericidal Concentration/Minimum Fungicidal Concentration, MBC/MFC: 11.25-75 µg/mL).

Metabolites Produced by Alkaliphiles with Potential Biotechnological Applications

Alkaliphiles are a diverse group of relatively less known microorganisms living in alkaline environments. To thrive in alkaline environments, alkaliphiles require special adaptations. This adaptation may have evolved metabolites which can be useful for biotechnological processes or other applications. In fact, certain metabolites are found unique to alkaliphiles or are effectively produced by alkaliphiles. This probably aroused the interest in metabolites of alkaliphiles. During recent years, many alkaliphilic microbes have been isolated, especially in countries having alkaline environments, like soda lakes. Even if the number of such isolated alkaliphiles is large, their metabolites have not yet been extensively analyzed and exploited. This is expected to come in the years ahead. So far, the focus of interests in metabolites from alkaliphiles falls into categories such as organic acids, ingredients for foodstuffs and cosmetics, antibiotics, and substances which modify properties of other materials used in industry. This chapter deals with biotechnologically important metabolites of alkaliphiles including compatible solutes, biosurfactants, siderophores, carotenoids, exopolysaccharides, and antimicrobial agents. It also covers the promising potential of alkaliphiles as sources of bioplastic raw materials. Moreover, an overview of the patent literature related to alkaliphiles is highlighted. Graphical Abstract.

The art of adapting to extreme environments: The model system Pseudoalteromonas

Extremophilic microbes have adapted to thrive in ecological niches characterized by harsh chemical/physical conditions such as, for example, very low/high temperature. Living organisms inhabiting these environments have developed peculiar mechanisms to cope with extreme conditions, in such a way that they mark the chemical-physical boundaries of life on Earth. Studying such mechanisms is stimulating from a basic research viewpoint and because of biotechnological applications. Pseudoalteromonas species are a group of marine gamma-proteobacteria frequently isolated from a range of extreme environments, including cold habitats and deep-sea sediments. Since deep-sea floors constitute almost 60% of the Earth's surface and cold temperatures represent the most common of the extreme conditions, the genus Pseudoalteromonas can be considered one of the most important model systems for studying microbial adaptation. Particularly, among all Pseudoalteromonas representatives, P. haloplanktis TAC125 has recently gained a central role. This bacterium was isolated from seawater sampled along the Antarctic ice-shell and is considered one of the model organisms of cold-adapted bacteria. It is capable of thriving in a wide temperature range and it has been suggested as an alternative host for the soluble overproduction of heterologous proteins, given its ability to rapidly multiply at low temperatures. In this review, we will present an overview of the recent advances in the characterization of Pseudoalteromonas strains and, more importantly, in the understanding of their evolutionary and chemical-physical strategies to face such a broad array of extreme conditions. A particular attention will be given to systems-biology approaches in the study of the above-mentioned topics, as genome-scale datasets (e.g. genomics, proteomics, phenomics) are beginning to expand for this group of organisms. In this context, a specific section dedicated to P. haloplanktis TAC125 will be presented to address the recent efforts in the elucidation of the metabolic rewiring of the organisms in its natural environment (Antarctica).

Comparing Spore Resistance of Bacillus Strains Isolated from Hydrothermal Vents and Spacecraft Assembly Facilities to Environmental Stressors and Decontamination Treatments

Submarine hydrothermal vents are inhabited by a variety of microorganisms capable of tolerating environmental extremes, making them ideal candidates to further expand our knowledge of the limitations for terrestrial life, including their ability to survive the exposure of spaceflight-relevant conditions. The spore resistance of two Bacillus spp. strains, APA and SBP3, isolated from two shallow vents off Panarea Island (Aeolian Islands, Italy), to artificial and environmental stressors (i.e., UVC radiation, X-rays, heat, space vacuum, hydrogen peroxide [H₂O₂], and low-pressure plasma), was compared with that of two close phylogenetic relatives (Bacillus horneckiae and Bacillus oceanisediminis). Additional comparisons were made with Bacillus sp. isolated from spacecraft assembly facilities (B. horneckiae, Bacillus pumilus SAFR-032, and Bacillus nealsonii) and the biodosimetry strain and space microbiology model organism Bacillus subtilis. Overall, a high degree of spore resistance to stressors was observed for the strains isolated from spacecraft assembly facilities, with an exceptional level of resistance seen by B. pumilus SAFR-032. The environmental isolate SBP3 showed a more robust spore resistance to UVC, X-rays, H₂O₂, dry heat, and space vacuum than the closely related B. horneckiae. Both strains (SBP3 and APA) were more thermotolerant than their relatives, B. horneckiae and B. oceanisediminis, respectively. SBP3 may have a novel use as a bacterial model organism for future interrogations into the potential of forward contamination in extraterrestrial environments (e.g., icy moons of Jupiter or Saturn), spacecraft sterilization and, broadly, microbial responses to spaceflight-relevant environmental stressors.

Thermostable enzymes and polysaccharides produced by thermophilic bacteria isolated from Bulgarian hot springs

Thermostable enzymes (thermozymes) have been recognized as extremophilic compounds with a greatest biotechnological importance in different industrial areas. Quite recently exopolysaccharides (EPSs) synthesized by thermophiles became an object of increased research interest due to their unique properties appropriate for some specific industrial needs. Thermophilic producers of biotechnologically valuable enzymes and novel EPS were isolated by our group from Bulgarian thermal springs with a diverse geotectonic origin and different water properties. Laboratory reactor processes for their production were developed in batch and continuous cultures. Some of the synthesized thermostable enzymes were among the first described in their groups, for example, the single known thermostable gellan lyase that demonstrated specific activity higher than that of the mesophilic enzymes. Isolated by us thermostable xylanase was able to degrade more than 60% of beechwood xylan in a coprocess with an archaeal β-xylosidase. Lipase purified by us was active between 55 and 90°C with an optimum at 75-80°C in a large pH range. It was able to degrade a broad range of substrates. Isolates from Bulgarian hot springs synthesized EPS with novel composition and high thermostability. Thus, Bulgarian hot springs harbor a wide set of thermophilic producers of novel enzymes and EPS with potential for a large number of biotechnological applications.

Engineering aspects of microbial exopolysaccharide production

Although the ability to secrete exopolysaccharides (EPS) is widespread among microorganisms, only a few bacterial (e.g. xanthan, levan, dextran) and fungal (e.g. pullulan) EPS have reached full commercialization. During the last years, other microbial EPS producers have been the subject of extensive research, including endophytes, extremophiles, microalgae and Cyanobacteria, as well as mixed microbial consortia. Those studies have demonstrated the great potential of such microbial systems to generate biopolymers with novel chemical structures and distinctive functional properties. In this work, an overview of the bioprocesses developed for EPS production by the wide diversity of reported microbial producers is presented, including their development and scale-up. Bottlenecks that currently hinder microbial EPS development are identified, along with future prospects for further advancement.

Microbial Diversity in Extreme Marine Habitats and Their Biomolecules

Extreme marine environments have been the subject of many studies and scientific publications. For many years, these environmental niches, which are characterized by high or low temperatures, high-pressure, low pH, high salt concentrations and also two or more extreme parameters in combination, have been thought to be incompatible to any life forms. Thanks to new technologies such as metagenomics, it is now possible to detect life in most extreme environments. Starting from the discovery of deep sea hydrothermal vents up to the study of marine biodiversity, new microorganisms have been identified, and their potential uses in several applied fields have been outlined. Thermophile, halophile, alkalophile, psychrophile, piezophile and polyextremophile microorganisms have been isolated from these marine environments; they proliferate thanks to adaptation strategies involving diverse cellular metabolic mechanisms. Therefore, a vast number of new biomolecules such as enzymes, polymers and osmolytes from the inhabitant microbial community of the sea have been studied, and there is a growing interest in the potential returns of several industrial production processes concerning the pharmaceutical, medical, environmental and food fields.

Role of Bacterial Exopolysaccharides as Agents in Counteracting Immune Disorders Induced by Herpes Virus

Extreme marine environments, such as the submarine shallow vents of the Eolian Islands (Italy), offer an almost unexplored source of microorganisms producing unexploited and promising biomolecules for pharmaceutical applications. Thermophilic and thermotolerant bacilli isolated from Eolian vents are able to produce exopolysaccharides (EPSs) with antiviral and immunomodulatory effects against Herpes simplex virus type 2 (HSV-2). HSV-2 is responsible for the most common and continuously increasing viral infections in humans. Due to the appearance of resistance to the available treatments, new biomolecules exhibiting different mechanisms of action could provide novel agents for treating viral infections. The EPSs hinder the HSV-2 replication in human peripheral blood mononuclear cells (PBMC) but not in WISH (Wistar Institute Susan Hayflic) cells line, indicating that cell-mediated immunity was involved in the antiviral activity. High levels of Th1-type cytokines were detected in PBMC treated with all EPSs, while Th2-type cytokines were not induced. These EPSs are water soluble exopolymers able to stimulate the immune response and thus contribute to the antiviral immune defense, acting as immunomodulators. As stimulants of Th1 cell-mediated immunity, they could lead to the development of novel drugs as alternative in the treatment of herpes virus infections, as well as in immunocompromised host.