Kinetics of production and characterization of the fucose-containing exopolysaccharide from Enterobacter A47

Challenges and opportunities in bioprocessing of gellan gum: A review

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

Cryoprotective Polysaccharides with Ordered Gel Structures Induce Ice Growth Anticipation and Survival Enhancement during Cell Cryopreservation

This work cross-correlated rheological, thermodynamic, and conformational features of several natural polysaccharides to their cryoprotective performance. The basis of cryoprotection of FucoPol, pectin, and agar revealed a causal combination of (i) an emerging sol-gel transition (p = 0.014) at near-hypothermia (4 °C), (ii) noncolligative attenuated supercooling of the kinetic freezing point of water (p = 0.026) supporting ice growth anticipation, and (iii) increased conformational order (p < 0.0001), where helix-/sheet-like features boost cryoprotection. FucoPol, of highest cryoprotective performance, revealed a predominantly helical structure (α/β = 1.5) capable of forming a gel state at 4 °C and the highest degree of supercooling attenuation (TH = 6.2 °C). Ice growth anticipation with gel-like polysaccharides suggests that the gel matrix neutralizes elastic deformations and lethal cell volumetric fluctuations during freezing, thus preventing the loss of homeostasis and increasing post-thaw viability. Ultimately, structured gels capable of attenuated supercooling enable cryoprotective action at the polymer-cell interface, in addition to polymer-ice interactions. This rationale potentiates implementing alternative, biobased, noncytotoxic polymers in cryobiology.

Research progress on the functions, preparation and detection methods of l-fucose

l-fucose is a six-carbon sugar that has potential applications in many fields. It exerts antitumor effects and could relieve intestinal disease. It exhibits potential as an emulsifier in the food industry. It is also used as a functional food and in anti-aging skincare products. However, at present, it is not possible to prepare high-purity l-fucose on a large scale, and its preparation needs further development. This review summarizes the preparation methods of l-fucose including chemical synthesis, enzymatic synthesis, microbial fermentation, and separation and purification from algae. The detection methods of l-fucose are also introduced in detail, such as l-fucose-specific lectin, detection l-fucose dehydrogenase, cysteine-sulfuric acid method, high-performance liquid chromatography, gas chromatography, and biosensors. In this review, the properties and pharmacological effects of l-fucose; preparation methods, and the commonly used detection methods of l-fucose are reviewed to serve as a reference material.

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.

Deacetylation and Desuccinylation of the Fucose-Rich Polysaccharide Fucopol: Impact on Biopolymer Physical and Chemical Properties

FucoPol is an acylated polysaccharide with demonstrated valuable functional properties that include a shear thinning fluid behaviour, a film-forming capacity, and an emulsion forming and stabilizing capacity. In this study, the different conditions (concentration, temperature, and time) for alkaline treatment were investigated to deacylate FucoPol. Complete deacetylation and desuccinylation was achieved with 0.02 M NaOH, at 60 °C for 15 min, with no significant impact on the biopolymer’s sugar composition, pyruvate content, and molecular mass distribution. FucoPol depyruvylation by acid hydrolysis was attempted, but it resulted in a very low polymer recovery. The effect of the ionic strength, pH, and temperature on the deacetylated/desuccinylated polysaccharide, d-FucoPol, was evaluated, as well as its emulsion and film-forming capacity. d-FucoPol aqueous solutions maintained the shear thinning behaviour characteristic of FucoPol, but the apparent viscosity decreased significantly. Moreover, contrary to FucoPol, whose solutions were not affected by the media’s ionic strength, the d-FucoPol solutions had a significantly higher apparent viscosity for a higher ionic strength. On the other hand, the d-FucoPol solutions were not affected by the pH in the range of 3.6–11.5, while FucoPol had a decreased viscosity for acidic pH values and for a pH above 10.5. Although d-FucoPol displayed an emulsification activity for olive oil similar to that of FucoPol (98 ± 0%) for an oil-to-water ratio of 2:3, the emulsions were less viscous. The d-FucoPol films were flexible, with a higher Young′s modulus (798 ± 152 MPa), a stress at the break (22.5 ± 2.5 MPa), and an elongation at the break (9.3 ± 0.7%) than FucoPol (458 ± 32 MPa, 15.5 ± 0.3 MPa and 8.1 ± 1.0%, respectively). Given these findings, d-FucoPol arises as a promising novel biopolymer, with distinctive properties that may render it useful for utilization as a suspending or emulsifier agent, and as a barrier in coatings and packaging films.

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.

Enhanced Control over Ice Nucleation Stochasticity Using a Carbohydrate Polymer Cryoprotectant

Metastable supercooling has emerged as a transformative technique for ice-free biopreservation, but issues of stability inherent to the stochastic nature of ice formation have thus far limited its translation out of the laboratory. In this work, we explore the influence of the bio-based carbohydrate polymer FucoPol on aqueous supercooling using an isochoric nucleation detection technique. We show that FucoPol, a high-molecular-weight, fucose-rich polysaccharide, which has previously been shown to reduce average ice crystal sizes after nucleation, also induces a concentration-dependent stabilization of metastable supercooled water, as evidenced by both a significant reduction in nucleation stochasticity (i.e., the spread in temperatures over which the system will nucleate upon cooling) and a corresponding increase in the predicted induction time of nucleation. FucoPol is found to confine the stochasticity of ice nucleation to a narrow, well-defined band of temperatures roughly one-third as wide as that of pure water under identical conditions. Importantly, this substantial reduction in stochasticity is accompanied by only a minimal (<1 °C) change in the average nucleation temperature, suggesting that this effect is distinct from colligative freezing point depression. Reducing and characterizing the stochasticity of aqueous supercooling is essential to the engineering design of practical biopreservation protocols, and the results reported herein suggest that high-viscosity polymer systems may provide a powerful and largely unexplored lever by which to manipulate metastable-equilibrium phase change kinetics at subzero temperatures.

Preparation and Characterization of Electrospun Polysaccharide FucoPol-Based Nanofiber Systems

The electrospinnability of FucoPol, a bacterial exopolysaccharide, is presented for the first time, evaluated alone and in combination with other polymers, such as polyethylene oxide (PEO) and pullulan. The obtained fibers were characterized in terms of their morphological, structural and thermal properties. Pure FucoPol fibers could not be obtained due to FucoPol’s low water solubility and a lack of molecular entanglements. Nanofibers were obtained via blending with PEO and pullulan. FucoPol:PEO (1:3 w/w) showed fibers with well-defined cylindrical structure, since the higher molecular weight of PEO helps the continuity of the erupted jet towards the collector, forming stable fibers. WAXS, DSC and TGA showed that FucoPol is an amorphous biopolymer, stable until 220 °C, whereas FucoPol-PEO fibers were stable until 140 °C, and FucoPol:pullulan fibers were stable until 130 °C. Interestingly, blended components influenced one another in intermolecular order, since new peaks associated to intermolecular hierarchical assemblies were seen by WAXS. These results make FucoPol-based systems viable candidates for production of nanofibers for packaging, agriculture, biomedicine, pharmacy and cosmetic 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.

Bacterial Succinoglycans: Structure, Physical Properties, and Applications

Succinoglycan is a type of bacterial anionic exopolysaccharide produced from Rhizobium, Agrobacterium, and other soil bacteria. The exact structure of succinoglycan depends in part on the type of bacterial strain, and the final production yield also depends on the medium composition, culture conditions, and genotype of each strain. Various bacterial polysaccharides, such as cellulose, xanthan, gellan, and pullulan, that can be mass-produced for biotechnology are being actively studied. However, in the case of succinoglycan, a bacterial polysaccharide, relatively few reports on production strains or chemical and structural characteristics have been published. Physical properties of succinoglycan, a non-Newtonian and shear thinning fluid, have been reported according to the ratio of substituents (pyruvyl, succinyl, acetyl group), molecular weight (M_w), and measurement conditions (concentration, temperature, pH, metal ion, etc.). Due to its unique rheological properties, succinoglycan has been mainly used as a thickener and emulsifier in the cosmetic and food industries. However, in recent reports, succinoglycan and its derivatives have been used as functional biomaterials, e.g., in stimuli-responsive drug delivery systems, therapeutics, and cell culture scaffolds. This suggests a new and expanded application of succinoglycan as promising biomaterials in biomedical fields, such as tissue engineering, regenerative medicine, and pharmaceuticals using drug delivery.

Antioxidant Potential of the Bio-Based Fucose-Rich Polysaccharide FucoPol Supports Its Use in Oxidative Stress-Inducing Systems

Reactive oxygen species (ROS) are dangerous sources of macromolecular damage. While most derive from mitochondrial oxidative phosphorylation, their production can be triggered by exogenous stresses, surpassing the extinction capacity of intrinsic antioxidant defense systems of cells. Here, we report the antioxidant activity of FucoPol, a fucose-rich polyanionic polysaccharide produced by Enterobacter A47, containing ca. 17 wt% of negatively charged residues in its structure. Ferric reducing antioxidant power (FRAP) assays coupled to Hill binding kinetics fitting have shown FucoPol can neutralize ferricyanide and Fe3+-TPTZ species at an EC50 of 896 and 602 µg/mL, respectively, with positive binding cooperativity (2.52 ≤ H ≤ 4.85). This reducing power is greater than most polysaccharides reported. Moreover, an optimal 0.25% w/v FucoPol concentration shown previously to be cryo- and photoprotective was also demonstrated to protect Vero cells against H2O2-induced acute exposure not only by attenuating metabolic viability decay, but also by accentuating post-stress proliferation capacity, whilst preserving cell morphology. These results on antioxidant activity provide evidence for the biopolymer's ability to prevent positive feedback cascades of the radical-producing Fenton reaction. Ultimately, FucoPol provides a biotechnological alternative for implementation in cryopreservation, food supplementation, and photoprotective sunscreen formula design, as all fields benefit from an antioxidant functionality.

Development of a Cryoprotective Formula Based on the Fucose-Containing Polysaccharide FucoPol

This study reports the performance of the polysaccharide FucoPol as an enhancer of cryoprotective formulations. FucoPol at a concentration of 0.25% (w/v) was added to several normothermic Dulbecco-derived solutions and hypothermic Euro-Collins, Custodiol-HTK, and Unisol-CV media, substituting some constituents in the latter class to develop FucoPol-based formulations that were tested for their ability to cryopreserve Vero cells. Supplementation yielded post-thaw cell recovery enhancements of at least 70% and averaged at 82%. The FucoPol-supplemented formulations Dulbecco(+)^+FP and Unisol-CV_S3 achieved cell viabilities capable of competing with the commercial cryogenic formula CryoStor CS5. Particularly in Unisol-CV_S3, mannitol, glucose, gluconate, and dextran were all substituted by 0.25% FucoPol, and still, a similar viability was achieved. Multiparametric correlation clustering showed that FucoPol cryoprotection synergizes best with K⁺, Ca²⁺, and Cl^- in its microenvironment. Component substitution analysis demonstrated that FucoPol acts consistently as a cryoprotectant, an impermeant, and a colloidal stabilizer, providing a combined alternative to glucose, mannitol, gluconate, and dextran, thus highlighting its potential in the development of high-performing cryoprotective formulas.

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.

Structural characterization and functional properties of novel exopolysaccharide from the extremely halotolerant Halomonas elongata S6

Production of extracellular polysaccharides by halophilic Archaea and Bacteria has been widely reported and the members of the genus Halomonas have been identified as the most potential producers. In the present work, a novel exopolysaccharide (EPS-S6) produced by the extremely halotolerant newly isolated Halomonas elongata strain S6, was characterized. According to the HPAE-PAD results, EPS-S6 was mainly composed of glucosamine, mannose, rhamnose and glucose (1:0.9:0.7:0.3). EPS-S6 was highly negatively charged and its molecular weight was about 270 kDa. Studies on its functional properties showed that EPS-S6 had several potential features. It has noticeable antioxidant activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) inhibition and DNA protection, good ability to inhibit and to disrupt pathogenic biofilms, excellent flocculation of kaolin suspension and interesting emulsifying properties at acidic, neutral and basic pH. Therefore, EPS-S6 could have potential biotechnological concern in several fields such as in food, cosmetic and environmental industries.

Demonstration of the cryoprotective properties of the fucose-containing polysaccharide FucoPol

We report the cryoprotective potential of FucoPol, a fucose-containing bacterial exopolysaccharide produced by Enterobacter A47. In vitro cryopreservation assays of Vero, Saos-2, HFFF2 and C2C12 cell lines exposed to a validated non-cytotoxic 2.5 mg/mL FucoPol concentration demonstrated a consistent post-thaw metabolic viability increase. Calorimetric analysis showed a non-colligative, FucoPol concentration-dependent increase of the freezing point (T_f), with minimal change in melting point (T_m). Freezing point variation was corroborated by Polarized Optical Microscopy studies, also showing a reduction of ice crystal dimensions. Its proven shear-thinning behaviour and polyanionicity favour interactivity between the polysaccharide and the water-ice interface, resulting in ice growth inhibition. These findings demonstrate FucoPol's high promise as a bio-based, biodegradable approach to be implemented into cryopreservation formulations.

Demonstration of the ability of the bacterial polysaccharide FucoPol to flocculate kaolin suspensions

In this study, the flocculation properties of FucoPol, a bacterial extracellular polysaccharide, were investigated. FucoPol is a high molecular weight polymer and negatively charged due to the presence of glucuronic acid and the acyl groups succinyl and pyruvyl. High flocculation rate values (>70%) were achieved with a low bioflocculant dosage of 1 mg/L, for pH values in the range 3-5 and temperature within 15-20°C. The bioflocculant was also shown to be stable after freezing/thawing and heating up to 100°C. Given the polymer's anionic character, the size of flocs formed and their surface profile, bridging seems to be the main flocculation mechanism of FucoPol. This study demonstrated that FucoPol is a promising natural, biodegradable and biocompatible alternative to the currently used synthetic or inorganic hazardous products, with potential to be used as a novel flocculation agent in several applications, such as water treatment, food or mining. Further studies will involve evaluating the reduction of cation dosage on flocculation efficiency, as well as testing the applicability of FucoPol to flocculate different types of suspended solids, such as, for example, activated carbons, soil solids or yeast cells.

Polysaccharide-based component and their relevance in edible film/coating: a review

Purpose

The purpose of this paper is to present an overview of functional properties of the polysaccharide-based component and their application in developing edible film and coating for the food processing sector.

Design/methodology/approach

In this review study, approximately 271 research and review articles focusing on studies related to polysaccharide-based components and their film-forming properties. This article also focused on the application of polysaccharide-based edible film in the food sector.

Findings

From the literature reviewed, polysaccharide components and components-based edible film/coating is the biodegradable and eco-friendly packaging of the materials and directly consumed by the consumer with food. It has been reported that the polysaccharide components have excellent properties such as being nontoxic, antioxidant, antimicrobial, antifungal and with good nutrients. The polysaccharide-based edible film has lipid and gas barrier properties with excellent transparency and mechanical strength. In various studies, researchers worked on the development of polysaccharide-based edible film and coating by incorporating plant based natural antioxidants. This was primarily done for obtaining improved physical and chemical properties of the edible film and coating. In future, the technology of developing polysaccharide-based edible film and coating could be used for extending the shelf life and preserving the quality of fruits and vegetables at a commercial level. There is more need to understand the role of edible packaging and sustainability in the food and environment sector.

Originality/value

Through this review paper, possible applications of polysaccharide-based components and their function property in the formation of the edible film and their effect on fruits, vegetables and other food products are discussed after detailed studies of literature from thesis and journal article.

Bioprospecting for Exopolysaccharides from Deep-Sea Hydrothermal Vent Bacteria: Relationship between Bacterial Diversity and Chemical Diversity

Many bacteria biosynthesize structurally diverse exopolysaccharides (EPS) and excrete them into their surrounding environment. The EPS functional features have found many applications in industries such as cosmetics and pharmaceutics. In particular, some EPS produced by marine bacteria are composed of uronic acids, neutral sugars, and N-acetylhexosamines, and may also bear some functional sulfate groups. This suggests that they can share common structural features with glycosaminoglycans (GAG) like the two EPS (HE800 and GY785) originating from the deep sea. In an attempt to discover new EPS that may be promising candidates as GAG-mimetics, fifty-one marine bacterial strains originating from deep-sea hydrothermal vents were screened. The analysis of the EPS chemical structure in relation to bacterial species showed that Vibrio, Alteromonas, and Pseudoalteromonas strains were the main producers. Moreover, they produced EPS with distinct structural features, which might be useful for targeting marine bacteria that could possibly produce structurally GAG-mimetic EPS.

Production of FucoPol by Enterobacter A47 using waste tomato paste by-product as sole carbon source

Out-of-specification tomato paste, a by-product from the tomato processing industry, was used as the sole substrate for cultivation of the bacterium Enterobacter A47 and production of FucoPol, a value-added fucose-rich extracellular polysaccharide. Among the different tested fed-batch strategies, pH-stat, DO-stat and continuous substrate feeding, the highest production (8.77gL^-1) and overall volumetric productivity (2.92gL^-1d^-1) were obtained with continuous substrate feeding at a constant flow rate of 11gh^-1. The polymer produced had the typical FucoPol composition (37mol% fucose, 27mol% galactose, 23mol% glucose and 12mol% glucuronic acid, with an acyl groups content of 13wt%). The average molecular weight was 4.4×10⁶Da and the polydispersity index was 1.2. This study demonstrated that out-of-specification tomato paste is a suitable low-cost substrate for the production of FucoPol, thus providing a route for the valorization of this by-product into a high-value microbial product.

Hybrid modeling of microbial exopolysaccharide (EPS) production: The case of Enterobacter A47

Enterobacter A47 is a bacterium that produces high amounts of a fucose-rich exopolysaccharide (EPS) from glycerol residue of the biodiesel industry. The fed-batch process is characterized by complex non-linear dynamics with highly viscous pseudo-plastic rheology due to the accumulation of EPS in the culture medium. In this paper, we study hybrid modeling as a methodology to increase the predictive power of models for EPS production optimization. We compare six hybrid structures that explore different levels of knowledge-based and machine-learning model components. Knowledge-based components consist of macroscopic material balances, Monod type kinetics, cardinal temperature and pH (CTP) dependency and power-law viscosity models. Unknown dependencies are set to be identified by a feedforward artificial neural network (ANN). A semiparametric identification schema is applied resorting to a data set of 13 independent fed-batch experiments. A parsimonious hybrid model was identified that describes the dynamics of the 13 experiments with the same parameterization. The final model is specific to Enterobacter A47 but can be easily extended to other microbial EPS processes.

Polysaccharide-Based Membranes in Food Packaging Applications

Plastic packaging is essential nowadays. However, the huge environmental problem caused by landfill disposal of non-biodegradable polymers in the end of life has to be minimized and preferentially eliminated. The solution may rely on the use of biopolymers, in particular polysaccharides. These macromolecules with film-forming properties are able to produce attracting biodegradable materials, possibly applicable in food packaging. Despite all advantages of using polysaccharides obtained from different sources, some drawbacks, mostly related to their low resistance to water, mechanical performance and price, have hindered their wider use and commercialization. Nevertheless, with increasing attention and research on this field, it has been possible to trace some strategies to overcome the problems and recognize solutions. This review summarizes some of the most used polysaccharides in food packaging applications.

An extracellular polymer at the interface of magnetic bioseparations

FucoPol, a fucose-containing extracellular polysaccharide (EPS) produced by bacterium Enterobacter A47 using glycerol as the carbon source, was employed as a coating material for magnetic particles (MPs), which were subsequently functionalized with an artificial ligand for the capture of antibodies. The performance of the modified MPs (MP-EPS-22/8) for antibody purification was investigated using direct magnetic separation alone or combined with an aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and dextran. In direct magnetic capturing, and using pure protein solutions of human immunoglobulin G (hIgG) and bovine serum albumin (BSA), MP-EPS-22/8 bound 120 mg hIgG g(-1) MPs, whereas with BSA only 10 ± 2 mg BSA g(-1) MPs was achieved. The hybrid process combining both the ATPS and magnetic capturing leads to a good performance for partitioning of hIgG in the desired phase as well as recovery by the magnetic separator. The MPs were able to bind 145 mg of hIgG g(-1) of particles which is quite high when compared with direct magnetic separation. The theoretical maximum capacity was calculated to be 410 ± 15 mg hIgG adsorbed g(-1) MPs with a binding affinity constant of 4.3 × 10(4) M(-1). In multiple extraction steps, the MPs bound 92% of loaded hIgG with a final purity level of 98.5%. The MPs could easily be regenerated, recycled and re-used for five cycles with only minor loss of capacity. FucoPol coating allowed both electrostatic and hydrophobic interactions with the antibody contributing to enhance the specificity for the targeted products.

Extracellular polymeric substances production kinetics of 13 sludge isolates using wastewater sludge as raw material and its flocculation potential

The kinetics of batch fermentation of 13 extracellular polymeric substances (EPS) producing bacterial strains (9 Bacillus, 2 Serratia and 2 Yersinia) were carried out using sterilized sludge as a raw material. The most of Bacillus (µ(max): 0.11-0.27 h⁻¹), Serratia (µ(max): 0.23-0.27 h⁻¹) and Yersinia (µ(max): 0.18-0.19 h⁻¹) strains had capability to grow and produce EPS (1.36-2.12 g/L) in the sterilized sludge. In general, EPS production was mixed growth associated for all the bacterial strains cultivated independently. Bacillus sp. 7, Serratia sp. 2 and Yersinia sp. 2 produced higher concentration (1.95-2.12 g/L) of EPS than the other remaining bacterial strains. Protein and carbohydrate contents of EPS remained constant during fermentation. Broth EPS (B-EPS) exhibited high kaolin flocculation activity (≥ 75%) in most of the cases except Bacillus sp. 1, Bacillus sp. 5 and Bacillus sp. 9, respectively. In general, high flocculation activities (FAs) (≥ 75%), were attained using 1.31-1.70 mg B-EPS/g kaolin, 0.45-0.97 mg protein/g kaolin and 0.11-0.21 mg carbohydrates/g kaolin. The study suggests that further systematic exploration is required for optimizing the process of EPS production. EPS produced in the sludge can potentially be used for different water and wastewater treatments.

Submerged culture process for biomass and exopolysaccharide production by Antarctic yeast: some engineering considerations

Production of biomass and extracellular polysaccharide (EPS) from psychrophilic Sporobolomyces salmonicolor AL1 in a stirred bioreactor was studied. The aspects of production technical-scale parameters, namely, bioreactor flow field, biomass and EPS production rates, oxygen mass transfer per input power, as well as important product properties, such as rheology and stability of EPS mixtures, were considered. The bioprocess was found to proceed in non-Newtonian flow with consistency coefficient rising typically to 0.03 Pa.s(n) and flow index declining to 0.7. Flow modeling was carried out and showed good homogenization for substrate delivery at agitation rates exceeding 400 rpm. Agitation rates lower than 400 rpm were considered counterproductive due to flow field non-uniformity. The cell density reached 5 g/l and EPS production yield reached 5.5 g/l at production rate 0.057 g EPS/l per hour (0.01 g EPS/g biomass per hour). Oxygen uptake rate and oxygen transfer rate were in the range of 0.5-1.7 mmolO2/l per hour and 2-4.7 mmolO2/l per hour, respectively. The mass transfer coefficient at reaction conditions was found to be in the range [Formula: see text]. The bioprocess biological performance was higher at moderate agitation speed and revealed biomass diminution and cell inactivation by increasing impeller revolutions and shear rate. The product EPS was found to introduce shear-thinning behavior in water solutions with apparent viscosity of up to 30 mPa.s and to stabilize 1-2 % oil-in-water emulsions improving their lipophilic properties. The emulsion dispersion index was found to be comparable with the one of Arlacel 165, the emulsifier used in cosmetic. The long-term performance of the complex cream mixtures of the glucomannan prepared in commercial format was found promising for further application.

Study of the interactive effect of temperature and pH on exopolysaccharide production by Enterobacter A47 using multivariate statistical analysis

Enterobacter A47 synthesizes fucose-containing exopolysaccharides (EPS). Maximum EPS production (>7.00 g L(-1)) was obtained for temperature and pH within 25-35°C and 6.0-8.0, respectively. Under these conditions, the polymers contained over 30% fucose. Glucose, galactose, and glucuronic acid contents were about 28%, 25%, and 10%, respectively, and the total acyl groups content was about 20 wt.%. The average molecular weight (Mw) was around 4.0 × 10(6). Outside the optimal temperature and pH ranges, fucose, galactose and glucuronic acid, and the total acyl group contents were reduced, while the glucose content increased, new monomers (rhamnose and glucosamine) were detected, and the Mw increased to ≥ 1.10 × 10(7). This study revealed the ability of Enterobacter A47 to synthesize different heteropolysaccharides as a function of pH and temperature, a feature that can be exploited to obtain tailored polymer composition. Moreover, the production of high fucose content EPS was stable for wide pH and temperature ranges, which is important for the envisaged industrial development of the bioprocess.