Biosorption of Heavy Metals by the Bacterial Exopolysaccharide FucoPol

Exploring biosynthesis strategies to boost the yield of exopolysaccharide-protein blend from Bacillus arachidis SY8(T), an isolated native strain, as a potent adsorbent for heavy metals removal

This investigation centers on the synthesis of a polysaccharide-protein blend produced by an isolated native strain (99.12 % phylogenetic affinity with Bacillus arachidis SY8(T)). The primary objective was to investigate the production of extracellular polymeric substances (EPS) under diverse stress conditions, encompassing exposure to heavy metal ions, salt, and toxic agents. Additionally, the impact of environmental parameters, namely pH, inoculation percentage, and time, on the production was investigated. Subsequently, the study examined the biosorption potential of the EPS produced for Pb(II), Cu(II), and Mn(II). The EPS obtained was thoroughly characterized via various tests. Rheological evaluations of an EPS solution (2 wt%) confirmed its pseudo-plastic and non-Newtonian fluid properties, while TGA analysis demonstrated its thermal stability up to 600 °C. Additional analyses, including GPC, FTIR, and H-NMR, provide further insights into the produced EPS. The best conditions for EPS production are determined: 5 % NaCl salt, serving as an effective stress inducer, and 37 °C, pH 6, with a 5 % inoculation, over 96 h. EPS demonstrates remarkable removal efficiencies of 99.9, 99.4 and 78.9 % for Pb(II), Cu(II), and Mn(II), respectively. These findings highlight the potential of EPS as an effective agent for removing heavy metal ions.

Biosorption of arsenic (III) from aqueous solution using calcium alginate immobilized dead biomass of Acinetobacter sp. strain Sp2b

This study presents a novel biosorbent developed by immobilizing dead Sp2b bacterial biomass into calcium alginate (CASp2b) to efficiently remove arsenic (AsIII) from contaminated water. The bacterium Sp2b was isolated from arsenic-contaminated industrial soil of Punjab, a state in India. The strain was designated Acinetobacter sp. strain Sp2b as per the 16S rDNA sequencing, GenBank accession number -OP010048.The CASp2b was used for the biosorption studies after an initial screening for the biosorption capacity of Sp2b biomass with immobilized biomass in both live and dead states. The optimum biosorption conditions were examined in batch experimentations with contact time, pH, biomass, temperature, and AsIII concentration variables. The maximum biosorption capacity (qmax = 20.1 ± 0.76 mg/g of CA Sp2b) was obtained at pH9, 35 ̊ C, 20 min contact time, and 120 rpm agitation speed. The isotherm, kinetic and thermodynamic modeling of the experimental data favored Freundlich isotherm (R2 = 0.941) and pseudo-2nd-order kinetics (R2 = 0.968) with endothermic nature (ΔH° = 27.42) and high randomness (ΔS° = 58.1).The scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis indicated the As surface binding. The reusability study revealed the reasonable usage of beads up to 5 cycles. In conclusion, CASp2b is a promising, efficient, eco-friendly biosorbent for AsIII removal from contaminated water.

Mixed Consortium of Salt-Tolerant Phosphate Solubilizing Bacteria Improves Maize (Zea mays) Plant Growth and Soil Health Under Saline Conditions

The rhizobacterial isolate SP-167 exhibited considerable phosphate solubilization, IAA production, exo-polysaccharides, proline, APX, and CAT at a concentration of 6% NaCl (w/v). 16S rDNA sequencing and BLAST analysis showed that isolate SP-167 was Klebsiella sp. In this study, T2 and T8 consortium was developed on the basis of the compatibility of isolate SP-167 with Kluyvera sp. and Enterobacter sp. At 6% NaCl (w/v) concentration, T2 and T8 showed increased PGP properties such as phosphate solubilization, IAA, Proline activity, CAT, POD, and EPS than isolate SP-167. The maximum increase in shoot length was recorded in T2-treated maize plants as compared to the control after 60 days in 1% NaCl stress. The N, P, and K content of leaves were significantly increased in maize plants with the inoculation of both the T2 and T8 consortium. The electrical conductivity of soil was decreased significantly in the T2 inoculated 1% NaCl (w/v) treated pot after 30, 60, and 90 days. In this study, soil enzymes DHA and PPO were significantly increased in both T2 and T8 treated combinations. The Na concentration in root and shoot were significantly decreased in T8 inoculated plant than in T2, as confirmed by the translocation factor study.

Metal sequestration by Microcystis extracellular polymers: a promising path to greener water treatment

The problem of heavy metal pollution in water bodies poses a significant threat to both the environment and human health, as these toxic substances can persist in aquatic ecosystems and accumulate in the food chain. This study investigates the promising potential of using Microcystis aeruginosa extracellular polymeric substances (EPS) as an environmentally friendly, highly efficient solution for capturing copper (Cu2+) and nickel (Ni2+) ions in water treatment, emphasizing their exceptional ability to promote green technology in heavy metal sequestration. We quantified saccharides, proteins, and amino acids in M. aeruginosa biomass and isolated EPS, highlighting their metal-chelating capabilities. Saccharide content was 36.5 mg g-1 in biomass and 21.4 mg g-1 in EPS, emphasizing their metal-binding ability. Proteins and amino acids were also prevalent, particularly in EPS. Scanning electron microscopy (SEM) revealed intricate 3D EPS structures, with pronounced porosity and branching configurations enhancing metal sorption. Elemental composition via energy dispersive X-ray analysis (EDAX) identified essential elements in both biomass and EPS. Fourier transform infrared (FTIR) spectroscopy unveiled molecular changes after metal treatment, indicating various binding mechanisms, including oxygen atom coordination, π-electron interactions, and electrostatic forces. Kinetic studies showed EPS expedited and enhanced Cu2+ and Ni2+ sorption compared to biomass. Thermodynamic analysis confirmed exothermic, spontaneous sorption. Equilibrium biosorption studies displayed strong binding and competitive interactions in binary metal systems. Importantly, EPS exhibited impressive maximum sorption capacities of 44.81 mg g-1 for Ni2+ and 37.06 mg g-1 for Cu2+. These findings underscore the potential of Microcystis EPS as a highly efficient sorbent for heavy metal removal in water treatment, with significant implications for environmental remediation and sustainable water purification.

Bioprospecting for new exopolysaccharide-producing microalgae of marine origin

Microalgae are photosynthetic organisms that can produce biomolecules with industrial interest, including exopolysaccharides (EPS). Due to their structural and compositional diversity, microalgae EPS present interesting properties that can be considered in cosmetic and/or therapeutic areas. Seven microalgae strains from three different lineages, namely Dinophyceae (phylum Miozoa), Haptophyta, and Chlorophyta, were investigated as EPS producers. All strains were found to be EPS producers, though the highest EPS yield was obtained for Tisochrysis lutea, followed by Heterocapsa sp. (126.8 and 75.8 mg L-1, respectively). Upon assessment of the polymers' chemical composition, significant contents of unusual sugars, including fucose, rhamnose, and ribose, were found. Heterocapsa sp. EPS stood out due to its high content of fucose (40.9 mol%), a sugar known to confer biological properties to polysaccharides. The presence of sulfate groups (10.6-33.5 wt%) was also noticed in the EPS produced by all microalgae strains, thus contributing to the possibility that these EPS might have biological activities worth exploring.

Microencapsulation via Spray-Drying of Geraniol-Loaded Emulsions Stabilized by Marine Exopolysaccharide for Enhanced Antimicrobial Activity

The current study investigates the formation of microencapsulated geraniol powder, with the exopolysaccharide EPS-K1B3 produced by Halomonas caseinilytica K1, as wall material, using spray-drying. Evaluation of the antimicrobial activity of the functional emulsions, prepared at either pH 5 or pH 7, was carried out against Gram-positive (Listeria innocua (ATCC 33090)) and Gram-negative (Escherichia coli (DSM682)) bacterial strains. Results showed prolonged antimicrobial efficacy until 30 days of incubation for geraniol microcapsules compared to wet geraniol emulsions, which could confirm the ability of the spray-drying process to protect encapsulated geraniol for a longer period. The highest antimicrobial efficacy of geraniol microcapsules was observed against L. innocua at pH 5. Therefore, the influence of pH on the functional property of geraniol microcapsules could be highlighted beside the targeted bacterial strain.

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.

Preparation of Porous Scaffold Based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) and FucoPol

This work focused on the development of porous scaffolds based on biocomposites comprising two biodegradable and biocompatible biopolymers: a terpolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (PHBHVHHx), and the bacterial polysaccharide FucoPol. The PHBHVHHx terpolymer was composed of 3-hydroxybutyrate (55 wt%), 3-hydroxyvalerate (21 wt%), and 3-hydroxyhexanoate (24 wt%). This hydrophobic polyester has low crystallinity and can form elastic and flexible films. Fucopol is a fucose-containing water-soluble polysaccharide that forms viscous solutions with shear thinning behavior and has demonstrated emulsion-forming and stabilizing capacity and wound healing ability. Emulsion-templating was used to fabricate PHA-based porous structures in which FucoPol acted as a bioemulsifier. Compared with the scaffolds obtained from emulsions with only water, the use of FucoPol aqueous solutions resulted in structures with improved mechanical properties, namely higher tensile strength (4.4 MPa) and a higher Young's Modulus (85 MPa), together with an elongation at break of 52%. These features, together with the scaffolds' high porosity and pore interconnectivity, suggest their potential to sustain cell adhesion and proliferation, which is further supported by FucoPol's demonstrated wound healing ability. Therefore, the developed PHBHVHHx:FucoPol scaffolds arise as innovative porous bioactive structures with great potential for use in tissue engineering applications.

DNAzyme-templated exponential isothermal amplification for sensitive detection of lead pollution and high-throughput screening of microbial biosorbents

Very low concentrations of lead (Pb²⁺) pollution can have far-reaching adverse impacts on human health, due to the cumulative toxicity of Pb²⁺. Herein, we report a DNAzyme-templated exponential isothermal amplification strategy (termed DNAzymee) for the ultrasensitive detection of Pb²⁺ pollution and the high-throughput screening of microbial biosorbents to remove Pb²⁺ pollution. DNAzyme can specifically recognize Pb²⁺, and this recognition event can be amplified by the subsequent exponential isothermal amplification reaction (EXPAR) and monitored by a G-quadruplex specific dye. The proposed design showed a low limit of detection (95 pM) and could identify Pb²⁺ pollution in different real samples with high precision. In particular, the proposed assay was used to screen Pb²⁺ biosorbents, and the results showed that Leuconostoc mesenteroides is a promising microbial biosorbent for removing Pb²⁺ pollution. Thus, the DNAzymee assay can serve as a platform to monitor lead pollution in the environment and screen efficient biosorbents for the control of lead pollution.

An immobilized biosorbent from Paenibacillus dendritiformis dead cells and polyethersulfone for the sustainable bioremediation of lead from wastewater

Heavy metals, including lead, cause serious damage to human health and the surrounding environment. Natural biosorbents arise as environmentally friendly alternatives. In this study, two of the 41 isolates (8EF and 17OS) were the most efficient bacteria for growing on media supplemented with Pb²⁺ (1000 mg/L). At high concentrations up to 2000 mg/L, the pioneer isolate 17OS exhibited remarkable resistance to multiheavy metals. This isolate was identified as Paenibacillus dendritiformis 17OS and deposited in GenBank under accession number ON705726.1. Design-Expert was used to optimize Pb²⁺ metal removal by the tested bacteria. Results indicated that four of six variables were selected using a minimum-run resolution IV experimental design, with a significant affecting Pb²⁺ removal. Temperature and Pb²⁺ concentration were significant positive influences, whereas incubation period and agitation speed were significant negative ones. The tested strain modulated the four significant variables for maximum Pb²⁺ removal using Box-Behnken design. The sequential optimization method was beneficial in increasing biosorption by 4.29%. Dead biomass of P. dendritiformis 17OS was embedded with polyethersulfone to get a hydrophilic adsorptive membrane that can separate Pb²⁺ easily from aqueous solutions. SEM images and FT-IR analysis proved that the new biosorbent possesses a great structure and a lot of surface functional groups with a negative surface charge of - 9.1 mV. The removal rate of 200 mg/L Pb²⁺ from water reached 98% using 1.5 g/L of the immobilized biosorbent. The adsorption isotherm studies were displayed to determine the nature of the reaction. The adsorption process was related to Freundlich isotherm which describes the multilayer and heterogeneous adsorption of molecules to the adsorbent surface. In conclusion, dead bacterial cells were immobilized on a polyether sulfone giving it the characteristics of a novel adsorptive membrane for the bioremediation of lead from wastewater. Thus this study proposed a new generation of adsorptive membranes based on polyethersulfone and dead bacterial cells.

Exo-polysaccharide producing bacteria can induce maize plant growth and soil health under saline conditions

Salt tolerant plant growth boosting rhizobacteria can play an important function in plant salinity stress mitigation. In the current investigation, only two rhizobacterial isolates out of 68 produced exo-polysaccharide at the fastest rate and exhibited plant growth promoting properties such as IAA, CAT, APX production, and phosphate solubilization at 6% NaCl (w/v) concentration. Both isolates had synergistic PGP features and were compatible with one another. Isolate SP-20 was identified as Kluyvera sp. and SP-203 was identified as Enterobacter sp. -by 16SrDNA sequencing. After 30, 60, and 90 days, the combination of SP-20 and SP-203 enhanced the physicochemical parameters in the maize plant in comparison to the control. By increasing soil enzymes like DHA and PPO, both isolates significantly improved the soil health matrix. When a group of these isolates were inoculated into 1% and 2% NaCl (w/v) supplemented soil, the absorption of Na in the shoot and root of maize plants was inhibited by around 50%. The BCF values for all treatments were less than TF, and the values of BCF and TF were less than one. Therefore, the present study illustrated that the novel native isolates play a remarkable role to mitigate salinity stress in maize plant.

Biosorption Characteristic and Cytoprotective Effect of Pb2+, Cu2+ and Cd2+ by a Novel Polysaccharide from Zingiber strioatum

The pollution of heavy metal ions can cause damage to the human body through food, so developing a new biocompatible material that can remove the damage of heavy metal ions has a good application prospect. In this study, we obtained a new homogeneous polysaccharide composed of seven monosaccharides from Zingiber strioatum by using the method of separation and purification of polysaccharide. The results of adsorption behavior showed that the concentration, temperature and pH value could affect the adsorption effect of Zingiber strioatum polysaccharide (ZSP). Through model fitting of the data of adsorption time and metal concentration, the pseudo second-order kinetic model can well describe the kinetics of the adsorption process, and the adsorption isotherm data fit well with the Langmuir model. In the preliminary research results of adsorption mechanism, SEM showed the appearance of ZSP as flake and porous surface; EDX analysis confirmed the metal adsorption capacity of ZSP. Meanwhile, XPS and FT-IR further clarified the adsorption based on functional groups composed of C and O. The cells preprotected by ZSP can resist heavy metal ions. The above results show that ZSP can be used as a new macromolecule to bind heavy metal ions, which can broaden the research scope of polysaccharides in contaminated food systems.

Biosorption of heavy metals by microorganisms: Evaluation of different underlying mechanisms

Globally, ecotoxicologists, environmental biologists, biochemists, pathologists, and other experts are concerned about environmental contamination. Numerous pollutants, such as harmful heavy metals and emerging hazardous chemicals, are pervasive sources of water pollution. Water pollution and sustainable development have several eradication strategies proposed and used. Biosorption is a low-cost, easy-to-use, profitable, and efficient method of removing pollutants from water resources. Microorganisms are effective biosorbents, and their biosorption efficacy varies based on several aspects, such as ambient factors, sorbing materials, and metals to be removed. Microbial culture survival is also important. Biofilm agglomerates play an important function in metal uptake by extracellular polymeric molecules from water resources. This study investigates the occurrence of heavy metals, their removal by biosorption techniques, and the influence of variables such as those indicated above on biosorption performance. Ion exchange, complexation, precipitation, and physical adsorption are all components of biosorption. Between 20 and 35 °C is the optimal temperature range for biosorption efficiency from water resources. Utilizing living microorganisms that interact with the active functional groups found in the water contaminants might increase biosorption efficiency. This article discusses the negative impacts of microorganisms on living things and provides an outline of how they affect the elimination of heavy metals.

Development of Olive Oil and α-Tocopherol Containing Emulsions Stabilized by FucoPol: Rheological and Textural Analyses

Biobased raw materials like natural polysaccharides are increasingly sought by the cosmetic industry for their valuable properties. Such biodegradable and usually non-cytotoxic biopolymers are commonly used in skin-care products as rheological modifiers, bioemulsifiers and/or bioactive ingredients. FucoPol is a natural polysaccharide with reported biocompatibility, emulsion-forming and stabilizing capacity, shear-thinning behavior and bioactivity (e.g., antioxidant capacity, wound healing ability) that potentiate its utilization in skin-care products. In this study, olive oil and α-tocopherol containing emulsions were stabilized with FucoPol. Although the presence of α-tocopherol negatively impacted the emulsions’ stability, it increased their emulsification index (EI). Moreover, FucoPol outperformed the commercial emulsifier Sepigel^® 305, under the tested conditions, with higher EI and higher stability under storage for 30 days. The formulation of FucoPol-based emulsions with olive oil and α-tocopherol was studied by Response Surface Methodology (RSM) that allowed the definition of the ingredients’ content to attain high emulsification. The RSM model established that α-tocopherol concentration had no significant impact on the EI within the tested ranges, with optimal emulsification for FucoPol concentration in the range 0.7–1.2 wt.% and olive oil contents of 20–30 wt.%. Formulations with 25 wt.% olive oil and either 0.5 or 2.0 wt.% α-tocopherol were emulsified with 1.0 wt.% or 0.7 wt.% FucoPol, respectively, resulting in oil-in-water (O/W) emulsions. The emulsions had similar shear-thinning behavior, but the formulation with higher FucoPol content displayed higher apparent viscosity, higher consistency, as well as higher firmness, adhesiveness and cohesiveness, but lower spreadability. These findings show FucoPol’s high performance as an emulsifier for olive oil/α-tocopherol, which are supported by an effective impact on the physicochemical and structural characteristics of the emulsions. Hence, this natural polysaccharide is a potential alternative to other emulsifiers.

The role of microplastics biofilm in accumulation of trace metals in aquatic environments

Microplastics are one of the major contaminants of aquatic nature where they can interact with organic and inorganic pollutants, including trace metals, and adsorb them. At the same time, after the microplastics have entered the aquatic environments, they are quickly covered with a biofilm - microorganisms which are able to produce extracellular polymeric substances (EPS) that can facilitate sorption of trace metals from surrounding water. The microbial community of biofilm contains bacteria which synthesizes EPS with antimicrobial activity making them more competitive than other microbial inhabitants. The trace metal trapping by bacterial EPS can inhibit the development of certain microorganisms, therefore, a single microparticle participates in complex interactions of the diverse elements surrounding it. The presented review aims to consider the variety of interactions associated with the adsorption of trace metal ions on the surface of microplastics covered with biofilm, the fate of such microplastics and the ever-increasing risk to the environment caused by the combination of these large-scale pollutants - microplastics and trace metals. Since aquatic pollution problems affect the entire planet, strict regulation of the production, use, and disposal of plastic materials is needed to mitigate the effects of this emerging pollutant and its complexes could have on the environment and human health.

Adsorption behavior and mechanism of Lead (Pb2+) by sulfate polysaccharide from Enteromorpha prolifera

Lead (Pb²⁺) pollution poses severe healthy and ecological risks to humans. In this work, sulfate polysaccharide from Enteromorpha prolifera (SPE) was utilized for Pb²⁺ adsorption from simulated intestinal fluid. In order to evaluate its adsorption behaviors comprehensively, batch adsorption of Pb²⁺ was investigated under different conditions. Results showed that SPE presents high adsorption ability for Pb²⁺ through chemical adsorption process and the maximum adsorption capacity for Pb²⁺ was 278.5 mg/g. And SPE exhibited higher removal efficiency (≥60%) for trace Pb²⁺ (<10 mg/L) compared to that of other adsorbents based on polysaccharide. Besides, its adsorption can be described by Langmuir isotherm and pseudo-second-order kinetic models. Further, XRD, FTIR, and XPS were used to characterize the possible interaction of Pb²⁺ with SPE, and the results showed that carboxyl and hydroxyl groups in SPE play more important role than that of sulfate group. Our work represents the first assessment of Pb²⁺ adsorption properties of SPE. This investigation highlights the potential application of SPE to protect the body from hazard of food-derived heavy metals.

Hybrid Catalysts from Copper Biosorbing Bacterial Strains and Their Recycling for Catalytic Application in the Asymmetric Addition Reaction of B2(pin)2 on α,β-Unsaturated Chalcones

The recycling of heavy metal contaminants from wastewater as a source of valuable products perfectly fits with the principles of a Circular Economy system in view of restoring pollutants back into the system endowed with new social and economic benefits. Heavy metals are often present in such a low concentration that it makes the removal efficiency difficult to realize through the conventional physicochemical methods with high selectivity. Biosorption, conversely, by EPSs (extracellular polymeric substances) produced by several bacterial cells’ strains, is gaining a great deal of attention as an economic, efficient and sustainable depolluting process of wastewater from metal cations such as copper. Metal coordination to EPS components was thus deeply investigated by 1H NMR titration experiments. The 1,10–Phenanthroline–copper complex was exploited for quantifying the ability of different strains to sequester copper by a practical UV-Vis spectrophotometric method. The obtained data distinguished Serratia plymuthica strain SC5II as the bacterial strain displaying copper-adsorbing properties higher than any other, with Stenotrophomonas sp. strain 13a resulting in the worst one. Different analytical techniques, i.e., Dynamic Light Scattering (DLS), FT-IR analysis and SEM spectroscopy were thus employed to rationalize these results. Finally, the obtained copper chelates were successfully employed as hybrid catalysts in the asymmetric boron addition to α,β-unsaturated chalcones for the synthesis of valuable pharmaceutical intermediates, thus placing waste management in a new circular perspective.

Sustainable use of agro-industrial wastes as potential feedstocks for exopolysaccharide production by selected Halomonas strains

Large quantities of waste biomass are generated annually worldwide by many industries and are vastly underutilized. However, these wastes contain sugars and other dissolved organic matter and therefore can be exploited to produce microbial biopolymers. In this study, four selected Halomonas strains, namely, Halomonas caseinilytica K1, Halomonas elongata K4, Halomonas smyrnensis S3, and Halomonas halophila S4, were investigated for the production of exopolysaccharides (EPS) using low-cost agro-industrial wastes as the sole carbon source: cheese whey, grape pomace, and glycerol. Interestingly, both yield and monosaccharide composition of EPS were affected by the carbon source. Glucose, mannose, galactose, and rhamnose were the predominant monomers, but their relative molar ratio was different. Similarly, the average molecular weight of the synthesized EPS was affected, ranging from 54.5 to 4480 kDa. The highest EPS concentration (446 mg/L) was obtained for H. caseinilytica K1 grown on cheese whey that produced an EPS composed mostly of galactose, rhamnose, glucose, and mannose, with lower contents of galacturonic acid, ribose, and arabinose and with a molecular weight of 54.5 kDa. Henceforth, the ability of Halomonas strains to use cost-effective substrates, especially cheese whey, is a promising approach for the production of EPS with distinct physicochemical properties suitable for various applications.

Extraction of the Bacterial Extracellular Polysaccharide FucoPol by Membrane-Based Methods: Efficiency and Impact on Biopolymer Properties

In this study, membrane-based methods were evaluated for the recovery of FucoPol, the fucose-rich exopolysaccharide (EPS) secreted by the bacterium Enterobacter A47, aiming at reducing the total water consumption and extraction time, while keeping a high product recovery, thus making the downstream procedure more sustainable and cost-effective. The optimized method involved ultrafiltration of the cell-free supernatant using a 30 kDa molecular weight cut-off (MWCO) membrane that allowed for a 37% reduction of the total water consumption and a 55% reduction of the extraction time, compared to the previously used method (diafiltration-ultrafiltration with a 100 kDa MWCO membrane). This change in the downstream procedure improved the product’s recovery (around 10% increase) and its purity, evidenced by the lower protein (8.2 wt%) and inorganic salts (4.0 wt%) contents of the samples (compared to 9.3 and 8.6 wt%, respectively, for the previously used method), without impacting FucoPol’s sugar and acyl groups composition, molecular mass distribution or thermal degradation profile. The biopolymer’s emulsion-forming and stabilizing capacity was also not affected (emulsification activity (EA) with olive oil, at a 2:3 ratio, of 98 ± 0% for all samples), while the rheological properties were improved (the zero-shear viscosity increased from 8.89 ± 0.62 Pa·s to 17.40 ± 0.04 Pa·s), which can be assigned to the higher purity degree of the extracted samples. These findings demonstrate a significant improvement in the downstream procedure raising FucoPol’s recovery, while reducing water consumption and operation time, key criteria in terms of process economic and environmental sustainability. Moreover, those changes improved the biopolymer’s rheological properties, known to significantly impact FucoPol’s utilization in cosmetic, pharmaceutical or food products.

Characterization and Biotechnological Potential of Extracellular Polysaccharides Synthesized by Alteromonas Strains Isolated from French Polynesia Marine Environments

Marine environments comprise almost three quarters of Earth's surface, representing the largest ecosystem of our planet. The vast ecological and metabolic diversity found in marine microorganisms suggest that these marine resources have a huge potential as sources of novel commercially appealing biomolecules, such as exopolysaccharides (EPS). Six Alteromonas strains from different marine environments in French Polynesia atolls were selected for EPS extraction. All the EPS were heteropolysaccharides composed of different monomers, including neutral monosaccharides (glucose, galactose, and mannose, rhamnose and fucose), and uronic acids (glucuronic acid and galacturonic acid), which accounted for up to 45.5 mol% of the EPS compositions. Non-carbohydrate substituents, such as acetyl (0.5-2.1 wt%), pyruvyl (0.2-4.9 wt%), succinyl (1-1.8 wt%), and sulfate (1.98-3.43 wt%); and few peptides (1.72-6.77 wt%) were also detected. Thermal analysis demonstrated that the EPS had a degradation temperature above 260 °C, and high char yields (32-53%). Studies on EPS functional properties revealed that they produce viscous aqueous solutions with a shear thinning behavior and could form strong gels in two distinct ways: by the addition of Fe2+, or in the presence of Mg2+, Cu2+, or Ca2+ under alkaline conditions. Thus, these EPS could be versatile materials for different applications.

Bacterial survival strategies and responses under heavy metal stress: a comprehensive overview

Heavy metals bring long-term hazardous consequences and pose a serious threat to all life forms. Being non-biodegradable, they can remain in the food webs for a long period of time. Metal ions are essential for life and indispensable for almost all aspects of metabolism but can be toxic beyond threshold level to all living beings including microbes. Heavy metals are generally present in the environment, but many geogenic and anthropogenic activities has led to excess metal ion accumulation in the environment. To survive in harsh metal contaminated environments, bacteria have certain resistance mechanisms to metabolize and transform heavy metals into less hazardous forms. This also gives rise to different species of heavy metal resistant bacteria. Herein, we have tried to incorporate the different aspects of heavy metal toxicity in bacteria and provide an up-to-date and across-the-board review. The various aspects of heavy metal biology of bacteria encompassed in this review includes the biological notion of heavy metals, toxic effect of heavy metals on bacteria, the factors regulating bacterial heavy metal resistance, the diverse mechanisms governing bacterial heavy metal resistance, bacterial responses to heavy metal stress, and a brief overview of gene regulation under heavy metal stress.

Photoprotective effect of the fucose-containing polysaccharide FucoPol

This study reports the performance of FucoPol, a fucose-containing bacterial polysaccharide, as a photostable agent with high absorption yield at concentrations as low as 0.02 % (w/v). FucoPol is non-cytotoxic, efficiently protects from UVA and UVB at concentrations of 0.02-2 % (w/v) and 0.2-2 % (w/v), respectively, has over 94 % overall photostability up to 1.5 h of irradiation time. The lowest concentration studied (0.02 %, w/v) shows a sun protection factor (SPF) of 2.61 ± 0.08. The SPF-to-concentration unit ratio showed that FucoPol is about 60-fold more photoprotective than combinations of common organic and inorganic UV filters. In vitro radiation exposure experiments of adhered Vero epithelial and PM1 keratinocytic cells in the presence of 0.25 % (w/v) FucoPol further showed that cell viability was preserved, and delayed radiation-induced cell death was prevented. Overall, FucoPol outperforms common cosmetic biopolymers like xanthan and fucogel. These results are very promising for the development of bio-based sunscreen formulations.