Biosynthesis of novel exopolymers by Aureobasidium pullulans

Biofabrication of Functional Pullulan by Aureobasidium pullulans under the Effect of Varying Mineral Salts and Sugar Stress Conditions

Pullulan is a linear exopolysaccharide, produced in the fermentation media of Aureobasidium pullulans, with a variety of applications in the food and pharmaceutical industries. Pullulan derivatives have growing potential for biomedical applications, but the high cost of pullulan biofabrication currently restricts its commercial use. Better control over pullulan yield, molecular weight and melanin production by altering fermentation conditions could improve the economics. In this study, the effects of sugar and mineral salt stresses on the pullulan production of A. pullulans ATCC 42023 were examined in batch processes. The chemical structure of the recovered pullulan was characterized by FTIR and NMR spectroscopy, and the molecular weight distribution was obtained via SEC. Pullulan yield and melanin production varied when the conditions were adjusted, and pullulans with different molar masses were obtained. Higher-yield pullulan production and a lower polydispersity index were observed when CuSO4 was added to the fermentation in comparison with the control and with the addition of sugars and other salts. Biofabrication of pullulan under stress conditions is a promising strategy to enhance biopolymer yield and to obtain pullulan with a targeted molecular weight.

The Role of Extracellular Polymeric Substances in Micropollutant Removal

In biological wastewater treatment (WWT), microorganisms live and grow held together by a slime matrix comprised of extracellular polymeric substances (EPS), forming a three-dimensional microbial structure of aggregates (flocs or granules) and by chemical binding forces. Furthermore, microscopic observations showed that microbial cells within the flocs were cross linked with EPS, forming a network of polymers with pores and channels. The EPS are typically composed of organic substances such as polysaccharides (PS), proteins (PNs), humic acid substances (HAS), nucleic acids, and lipids. It has been established that EPS play an essential role in aggregate flocculation, settling, and dewatering. Moreover, in the presence of toxic substances, such as pharmaceutical compounds and pesticides, EPS form a protective layer for the aggregated biomass against environmental disturbances that might play an important role in the transport and transformation of micropollutants. Some researchers indicated that there is an increase in EPS concentration under toxic conditions, which can induce an increase in the size of microbial aggregates. In this contribution, we critically review the available information on the impact of micropollutants on microbial EPS production and the relationship between EPS and microbial aggregate structure. Also, a general definition, composition, and factors that affect EPS production are presented.

Bioremediation Potential of Streptomyces sp. MOE6 for Toxic Metals and Oil

Toxic metal contamination has serious effects on human health. Crude oil that may contain toxic metals and oil spills can further contaminate the environment and lead to increased exposure. This being the case, we chose to study the bio-production of inexpensive, environmentally safe materials for remediation. Streptomyces sp. MOE6 is a Gram-positive, filamentous bacterium from soil that produces an extracellular polysaccharide (MOE6-EPS). A one-factor-at-a-time experiments showed that the maximum production of MOE6-EPS was achieved at 35 °C, pH 6, after nine days of incubation with soluble starch and yeast extract as carbon sources and the latter as the nitrogen source. We demonstrated that MOE6-EPS has the capacity to remove toxic metals such as Co(II), Cr(VI), Cu(II) and U(VI) and from solution either by chelation and/or reduction. Additionally, the bacterium was found to produce siderophores, which contribute to the removal of metals, specifically Fe(III). Additionally, purified MOE6-EPS showed emulsifying activities against various hydrophobic substances, including olive oil, corn oil, benzene, toluene and engine oil. These results indicate that EPS from Streptomyces sp. MOE6 may be useful to sequester toxic metals and oil in contaminated environments.

Exploring the Role of Bacterial Extracellular Polymeric Substances for Sustainable Development in Agriculture

The incessant need to increase crop yields has led to the development of many chemical fertilizers containing NPK (nitrogen-phosphorous-potassium) which can degrade soil health in the long term. In addition, these fertilizers are often leached into nearby water bodies causing algal bloom and eutrophication. Bacterial secondary metabolites exuded into the extracellular space, termed extracellular polymeric substances (EPS) have gained commercial significance because of their biodegradability, non-toxicity, and renewability. In many habitats, bacterial communities faced with adversity will adhere together by production of EPS which also serves to bond them to surfaces. Typically, hygroscopic, EPS retain moisture in desiccating conditions and modulate nutrient exchange. Many plant growth-promoting bacteria (PGPR) combat harsh environmental conditions like salinity, drought, and attack of pathogens by producing EPS. The adhesive nature of EPS promotes soil aggregation and restores moisture thus combating soil erosion and promoting soil fertility. In addition, these molecules play vital roles in maintaining symbiosis and nitrogen fixation thus enhancing sustainability. Thus, along with other commercial applications, EPS show promising avenues for improving agricultural productivity thus helping to address land scarcity as well as minimizing environmental pollution.

The impact of biodegradable carbon sources on nutrients removal in post-denitrification biofilm reactors

Wastewater from households wastewater treatment plants (HWWTP) is discharged to the ground or to the surface waters. Special consideration should be given to the improvement of HWWTP effectiveness, particularly in relation to nutrients. The addition of biodegradable carbon sources to biofilm reactor, can enhance microbial activity but may also lead to filling clogging. The study aimed to compare 3 different organic substrates: acetic acid (commonly applied)and two untypical - citric acid and waste beer, under the same operational conditions in a post-denitrification biofilm reactor. The study investigated the impact of a type of organic substrate, low pH and time on: (1) biofilm growth, (2) the characteristics of extracellular polymeric substances (EPS), (3) the kinetics of nutrients removal and (4) reactor clogging. Results were referred to (5) the effectiveness of nutrients removal. The study demonstrated that low pH assured the development of a thinbiofilm. Citric acid ensured the lowest biomass volume, being by 53% lower than in the reactor with acetic acid and by as much as 61% lower than in the reactor with waste beer. The soluble EPS fraction prevailed in the total EPS in all reactors. The content of the tightly bound EPS fraction ranged from 26.93% (citric acid) to 36.32% (waste beer). Investigations showed also a high ratio of exoproteins to polysaccharide in all fractions, which indicated a significant role of proteins in developing a highly-proliferating biofilm. The treated wastewater met requirements of Polish regulations concerning COD and nitrogen concentrations.

Comparative pathogenicity of opportunistic black yeasts in Aureobasidium

Aureobasidium pullulans and A. melanogenum are black-yeast-like surface colonisers and are commonly encountered as contaminants in the hospital. The species are able to produce melanin which play a role in protection against environmental stress and irradiation. Aureobasidium melanogenum shows higher frequency in opportunistic infections compared to A. pullulans. Comparative pathogenicity of opportunistic black yeasts between Aureobasidium pullulans and A. melanogenum to explain the observed differences in frequency in infection. Degrees of melanisation and thermotolerance were measured, and virulence of strains from different sources was examined in Galleria mellonela and murine infection models. Aureobasidium melanogenum responds with increased melanisation to temperature stress and generally survives at 37°C, A. pullulans on average scored less on these parameters. In the murine model, differences between species were not significant, but the melanised A. melanogenum group showed the highest virulence. This result was not reproducible in Galleria mellonella larvae at 25°C. The A. melanogenum black group showed higher pathogenicity in murine model, indicating that the combination of melanisation and thermotolerance rather than species affiliation is instrumental. Galleria larvae did not survive very well at 37°C, and hence, this model is judged insufficient to detect the small virulence differences observed in Aureobasidium.

Osteogenic response of mesenchymal progenitor cells to natural polysaccharide nanogel and atelocollagen scaffolds: A spectroscopic study

A natural polysaccharide scaffold, referred to as "freeze-dry nanogel-crosslinked-porous" (FD-NanoCliP) gel, was tested in comparison with an atelocollagen scaffold with respect to osteogenesis versus the mouse mesenchymal progenitor cell line KUSA-A1. The amphiphilic polysaccharide network, engineered in its structure to fit chemically crosslinked nanogels as building blocks into a physically crosslinked porous gel, revealed a superior osteointegrative performance as compared to the soluble atelocollagen network and a peculiar c-plane orientation growth of apatite crystallites, which resembled the structure of natural enamel. Besides evaluating osteogenesis in the FD-NanoCliP gel scaffold, an additional purpose of this study was to assess its chemical composition at the nanoscale and, through its knowledge, to interpret the osteogenic response of mesenchymal cells. In addition to conventional (optical and electron) microscopy and biological evaluation kits, the peculiar chemistry of the FD-NanoCliP gel scaffold and the formation of apatite on it were characterized by means of several independent analytical probes at the molecular scale, which included Raman, cathodoluminescence, energy dispersive X-ray, and X-ray fluorescence spectroscopies. This body of information consistently provided evidence for a peculiar chemistry developed in osteogenesis at the polysaccharide scaffold surface. Such chemistry is not available in soluble atelocollagen and it is key in the superior bioactivity found in the polysaccharide network.

Morphology, composition and aggregation mechanisms of soft bioflocs in marine snow and activated sludge: A comparative review

Conditions that lead to marine snow formation and aggregates that constitute the marine snow have similarities with the soft bioflocs that form during wastewater treatment by activated sludge process. Analysis of the conditions and similarities of the soft bioflocs in these two aquatic environments provide insight for the processes that lead to formation and growth of hydrated aggregates consisting of both living and nonliving particles, their chemical and biolocial composition, settling/suspension behavior, and contributing factors for their structure and morphology. This literature review provides a comparative analysis of the soft aggregates that form in marine and wastewater environments to characterize the conditions for formation and growth of highly hydrated aggregates consisting of microorganisms, suspended solids and large molecules. The marine snow and bioflocs that form in wastewater are visually similar and even contain microorganisms that are of similar type (i.e., Zoogloea, filamentous bacteria). During wastewater treatment, the microorganisms are not stressed and exopolymeric substances (EPS) produced have shorter molecules and higher protein content while EPS produced by the marine organisms are significantly larger in molecular size (by orders of magnitude) and have higher carbohydrate content.

Exploiting extracellular polymeric substances (EPS) controlling strategies for performance enhancement of biological wastewater treatments: An overview

Extracellular polymeric substances (EPS) are present both outside of the cells and in the interior of microbial aggregates, and account for a main component in microbial aggregates. EPS can influence the properties and functions of microbial aggregates in biological wastewater treatment systems, and specifically EPS are involved in biofilm formation and stability, sludge behaviors as well as sequencing batch reactors (SBRs) granulation whereas they are also responsible for membrane fouling in membrane bioreactors (MBRs). EPS exhibit dual roles in biological wastewater treatments, and hence the control of available EPS can be expected to lead to changes in microbial aggregate properties, thereby improving system performance. In this review, current updated knowledge with regard to EPS basics including their formation mechanisms, important properties, key component functions as well as sub-fraction differentiation is given. EPS roles in biological wastewater treatments are also briefly summarized. Special emphasis is laid on EPS controlling strategies which would have the great potential in promoting microbial aggregates performance and in alleviating membrane fouling, including limitation strategies (inhibition of quorum sensing (QS) systems, regulation of environmental conditions, enzymatic degradation of key components, energy uncoupling etc.) and elevation strategies (enhancement of QS systems, addition of exogenous agents etc.). Those strategies have been confirmed to be feasible and promising to enhance system performance, and they would be a research niche that deserves further study.

Efficient production of pullulan by Aureobasidium pullulans grown on mixtures of potato starch hydrolysate and sucrose

Pullulan is a natural exopolysaccharide with many useful characteristics. However, pullulan is more costly than other exopolysaccharides, which limits its effective application. The purpose of this study was to adopt a novel mixed-sugar strategy for maximizing pullulan production, mainly using potato starch hydrolysate as a low-cost substrate for liquid-state fermentation by Aureobasidium pullulans. Based on fermentation kinetics evaluation of pullulan production by A. pullulans 201253, the pullulan production rate of A. pullulans with mixtures of potato starch hydrolysate and sucrose (potato starch hydrolysate:sucrose = 80:20) was 0.212 h⁻¹, which was significantly higher than those of potato starch hydrolysate alone (0.146 h⁻¹) and mixtures of potato starch hydrolysate, glucose, and fructose (potato starch hydrolysate:glucose:fructose = 80:10:10, 0.166 h⁻¹) with 100 g L⁻¹ total carbon source. The results suggest that mixtures of potato starch hydrolysate and sucrose could promote pullulan synthesis and possibly that a small amount of sucrose stimulated the enzyme responsible for pullulan synthesis and promoted effective potato starch hydrolysate conversion effectively. Thus, mixed sugars in potato starch hydrolysate and sucrose fermentation might be a promising alternative for the economical production of pullulan.

Solvent optimization for bacterial extracellular matrices: a solution for the insoluble

Ionic liquids enable solvent optimization for different biofilms through solubility parameter concept.

Extracellular polymeric substances of bacteria and their potential environmental applications

Biopolymers are considered a potential alternative to conventional chemical polymers because of their ease of biodegradability, high efficiency, non-toxicity and non-secondary pollution. Recently, extracellular polymeric substances (EPS, biopolymers produced by the microorganisms) have been recognised by many researchers as a potential flocculent for their applications in various water, wastewater and sludge treatment processes. In this context, literature information on EPS is widely dispersed and is very scarce. Thus, this review marginalizes various studies conducted so far about EPS nature-production-recovery, properties, environmental applications and moreover, critically examines future research needs and advanced application prospective of the EPS. One of the most important aspect of chemical composition and structural details of different moieties of EPS in terms of carbohydrates, proteins, extracellular DNA, lipid and surfactants and humic substances are described. These chemical characteristics of EPS in relation to formation and properties of microbial aggregates as well as degradation of EPS in the matrix (biomass, flocs etc) are analyzed. The important engineering properties (based on structural characteristics) such as adsorption, biodegradability, hydrophilicity/hydrophobicity of EPS matrix are also discussed in details. Different aspects of EPS production process such as bacterial strain maintenance; inoculum and factors affecting EPS production were presented. The important factors affecting EPS production include growth phase, carbon and nitrogen sources and their ratio, role of other nutrients (phosphorus, micronutrients/trace elements, and vitamins), impact of pH, temperature, metals, aerobic versus anaerobic conditions and pure and mixed culture. The production of EPS in high concentration with high productivity is essential due to economic reasons. Therefore, the knowledge about all the aspects of EPS production (listed above) is highly essential to formulate a logical and scientific basis for the research and industrial activities. One of the very important issues in the production/application/biodegradation of EPS is how the EPS is extracted from the matrix or a culture broth. Moreover, EPS matrix available in different forms (crude, loosely bound, tightly bound, slime, capsular and purified) can be used as a bioflocculant material. Several chemical and physical methods for the extraction of EPS (crude form or purified form) from different sources have been analyzed and reported. There is ample information available in the literature about various EPS extraction methods. Flocculability, dewaterability and biosorption ability are the very attractive engineering properties of the EPS matrix. Recent information on important aspects of these properties qualitatively as well as quantitatively has been described. Recent information on the mechanism of flocculation mediated by EPS is presented. Potential role of EPS in sludge dewatering and biosorption phenomenon has been discussed in details. Different factors influencing the EPS ability to flocculate and dewaterability of different suspensions have been included. The factors considered for the discussion are cations, different forms of EPS, concentration of EPS, protein and carbohydrate content of EPS, molecular weight of EPS, pH of the suspension, temperature etc. These factors were selected for the study based upon their role in the flocculation and dewatering mechanism as well the most recent available literature findings on these factors. For example, only recently it has been demonstrated that there is an optimum EPS concentration for sludge flocculation/dewatering. High or low concentration of EPS can lead to destabilization of flocs. Role of EPS in environmental applications such as water treatment, wastewater flocculation and settling, colour removal from wastewater, sludge dewatering, metal removal and recovery, removal of toxic organic compounds, landfill leachate treatment, soil remediation and reclamation has been presented based on the most recent available information. However, data available on environmental application of EPS are very limited. Investigations are required for exploring the potential of field applications of EPS. Finally, the limitations in the knowledge gap are outlined and the research needs as well as future perspectives are highlighted.

Production of pullulan by a thermotolerant aureobasidium pullulans strain in non-stirred fed batch fermentation process

Total 95 isolates of Aureobasidium pullulans were isolated from different flowers and leaves samples, out of which 11 thermotolerant strains produced pullulan. One thermotolerant non-melanin pullulan producing strain, designated as RG-5, produced highest pullulan (37.1±1.0 g/l) at 42^oC, pH 5.5 in 48h of incubation with 3% sucrose and 0.5% ammonium sulphate in a non-stirred fed batch fermentor of 6 liters capacity. The two liters of initial volume of fermentation medium was further fed with the 2 liters in two successive batches at 5 h interval into the fermentor. The sterile air was supplied only for 10h at the rate of 0.5 vvm.

Evaluation of medium composition and fermentation parameters on pullulan production by Aureobasidium pullulans

The goal of this study was to enhance pullulan production by evaluating the effects of different fermentation parameters. Various carbon sources and their concentrations, yeast extract (YE) concentrations, fermentation temperatures and various pH profiles were examined. The optimal growth condition for pullulan production by Aureobasidium pullulans has been found as 75 g/L of sucrose as carbon source, 3 g/L of YE and cultivation temperature at 30 (°)C. Under these conditions with an initial pH at 5, 20.7 g/L of final pullulan concentration and 0.22 g/L/h maximum production rate were obtained. Later on, various pH profiles, agitation speeds, aerations and fed-batch fermentation were evaluated. The results demonstrated that pullulan production was enhanced to 25.8 g/L after 7-day cultivation with a 0.68 -g/L/h maximum production rate. There was no significant improvement of pullulan production from fed-batch fermentation. The optimal kinetics parameters were as follows: initial pH at 2.0, switched to pH 5.0 after 72 h and kept constant; agitation speed at 200 rpm; aeration at 1.5 vvm. The quality analysis demonstrated that the pullulan content produced from optimal conditions was 94.5% and its viscosity was 2.3 centipoise (cP). Fourier transform infrared spectroscopy also suggested that pullulan dominated the produced exopolysaccharide.

Thermophilic bacteria from Mexican thermal environments: isolation and potential applications

Extremophiles are microorganisms that possess application possibilities in several industrial fields, including agricultural, chemical, laundry, pharmaceutical, food, petroleum and bioremediation. This work reports the isolation of 19 thermophilic, alkalitolerant and halotolerant bacterial strains from two thermal sites in Veracruz, México: El Carrizal thermal pool and Los Baños hot spring. These strains belong to the Geobacillus, Anoxybacillus and Aeribacillus genera. The strains produce lipases, proteases, and amylases under thermophilic conditions. They may have good potential for application in microbial enhanced oil recovery, since they are thermophilic and halotolerant, produce exopolymers (up to 11.8 mg/mg) and acids, show emulsifying activity (E24 up to 7.5%), and are able to grow in kerosene as carbon source; these strains may also be used in biodesulphurization since they can grow in dibenzothiophene producing 2-hydroxybiphenyl under thermophilic conditions (up to 2.9 mg/L).

Penicillin G acylase as chiral selector in CE using a pullulan-coated capillary

In the present study, penicillin G acylase (PGA), an enzyme belonging to the family of hydrolases, has been investigated as chiral selector in CE using the partial filling technique. Owing to the strong disposition of PGA to be adsorbed by the inner capillary wall, permanently coated capillaries were used to diminish both the protein-wall interactions and the EOF. In particular, the silica surface of the capillary was chemically coated by an antiadhesive and an hydrophilic layer of pullulan, a high-molecular-mass homopolysaccharide. The coating procedure consisted in the silanization with glycidoxypropyltrimethoxysilane and the subsequent coupling of the hydroxyl groups of pullulan onto the silanized capillary. Using this approach, a significant EOF suppression was obtained within a wide pH range (pH 3.0-9.0); this result was very important in order to find the suitable conditions for the application of partial filling technique. The optimization of partial filling was carried out by considering the effects of different experimental conditions (buffer pH, PGA concentration, and loading duration), on the migration time and enantioresolution of rac-ketoprofen. Under the selected conditions as: 100 mM sodium phosphate buffer (pH 5.5) containing 240 microM of PGA (partial filling of 120 s at a pressure of 50 mbar), a series of acidic compounds resulted to be enantioresolved in about 10 min. The long-term stability of the proposed coating was evaluated; more than 100 injections were performed without significant loss of reproducibility.

Adhesion of Aureobasidium pullulans Is Controlled by Uronic Acid Based Polymers and Pullulan

Aureobasidium pullulans is a potentially pathogenic microfungus that produces and secretes the polysaccharide pullulan and other biomacromolecules, depending on the microbe's physiological state. The role of these macromolecules in mediating adhesion and attachment were examined. Interfacial forces and adhesion affinities of A. pullulans were probed for early-exponential phase (EEP) and late-exponential phase (LEP) cells, using atomic force microscopy (AFM). Biochemical assays showed that A. pullulans produces both pullulan and a uronic acid based polymer. The pullulan is not produced until the LEP, and it can be removed by treatment with pullulanase. Both adhesion forces between the microbe and the AFM tip (silicon nitride) and attachment of the cells to quartz sand grains were controlled by the density of the uronic acid polymer. Uronic acid polymers doubled in density between the EEP and the LEP and were unaffected by the enzyme pullulanase. Retention to quartz in a packed column was quantified using the collision efficiency (alpha), the fraction of collisions between the microbes, and the sand grains, that result in attachment. Adhesion forces and retention on glass were well correlated, with these values being higher for EEP cells (F(adh) = 7.65 +/-4.67 nN; alpha = 1.15) than LEP (F(adh) = 2.94 +/- 0.75; alpha = 0.49) and LEP + pullulanase cells (F(adh) = 2.33 +/-2.01 nN; alpha = 0.43). Steric interactions alone do not describe the adhesion behavior of this fungus, but they do provide information regarding the length and density of the macromolecules studied.

Current knowledge on biosynthesis, biological activity, and chemical modification of the exopolysaccharide, pullulan

The article presents an overview of the latest advances in investigations of the biosynthesis, molecular properties, and associated biological activity of pullulan. The literature survey on the pullulan biosynthesis is intended to illustrate how the great variety of environmental conditions as well as variability in strain characteristics influences the metabolic pathways of the pullulan formation and effects structural composition of the biopolymer. Molecular properties of pullulan as alpha-(1-->4)- and alpha-(1-->6)-glucan are discussed in terms of similarities with amylose and dextran structures, and an emphasis is made on the inherent biological activity of pullulan molecules. The author also attempts to summarize the concepts, options, and strategies in chemical modification of the biopolymer and to delineate future prospects in designing new biologically active derivatives.

Flow field-flow fractionation and characterization of ionic and neutral polysaccharides of vegetable and microbial origin

The flow field-flow fractionation (FlFFF) analysis of a variety of neutral as well as ionic polysaccharides from plants and micro-organisms shows the generally broad distribution in molecular size of these polymers. This result is also obtained on a commercial sample of pullulan whose size distribution appears much wider than that of any of five standard fractions of the same polymer. Clear evidence of some physico-chemical properties of the polysaccharides is given by the study of the effect of the carrier ionic strength on salep, oxidized salep and konjac, carboxymethylcellulose and hyaluronic acid. While neutral polysaccharides, regardless of their origin, only slightly change size distribution in the presence of a simple electrolyte in solution, charged polymers, either naturally charged or chemically ionized, consistently exhibit very low retention levels in water which dramatically increase even at low salt concentrations. Exclusion mechanisms, including steric effects, are shown to be responsible for the anticipated retention times in water of these species that assume the expected statistical coil behavior only when electric charges are screened by the added electrolyte. Under these conditions, higher retention levels are obtained because the volume adjacent to the accumulation wall becomes more accessible to the sample during relaxation. On the basis of these findings, the elution behavior of a number of polysaccharide samples in-laboratory obtained from the fungus Aureobasidium pullulans under different incubation conditions is attributed to the presence of species varying in physico-chemical properties and molecular size.

New exopolysaccharides produced by Aureobasidium pullulans grown on glucosamine

The polysaccharides produced by Aureobasidium pullulans, grown using glucosamine as the carbon source, were investigated by means of methylation analysis, affinity chromatography and NMR spectroscopy. The results indicated that, besides a small amount of pullulan, this micro-organism was capable of producing-in low yields-mixtures of at least two different complex polysaccharides containing mainly mannose and galactose. (1)H NMR spectra of two fractions obtained by lectin affinity chromatography indicated that one polymer was constituted exclusively of mannose residues while the other contained both galactofuranosyl and mannopyranosyl residues.

Direct incorporation of glucosamine and N-acetylglucosamine into exopolymers by Gluconacetobacter xylinus (=Acetobacter xylinum) ATCC 10245: production of chitosan-cellulose and chitin-cellulose exopolymers

Gluconacetobacter xylinus (=Acetobacter xylinum) ATCC 10245 incorporated 2-amino-2-deoxy-D-glucose (glucosamine) and 2-acetamido-2-deoxy-D-glucose (N-acetylglucosamine), but not 3-O-methyl-D-glucose or 2-deoxy-D-glucose into exopolymers. Incorporation was confirmed by gas chromatography with and without mass spectrometry, Fourier transform infrared, and 1H nuclear magnetic resonance. The average molar percentage of glucosamine and N-acetylglucosamine in the exopolymers was about 18%.