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Scientific RepoRts | 7:41193 | DOI: 10.1038/srep41193
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Characterization of novel
Acidobacteria exopolysaccharides
with potential industrial and
ecological applications
Anna M. Kielak
1,*
, Tereza C. L. Castellane
2,*
, Joao C. Campanharo
2
, Luiz A. Colnago
3
,
Ohana Y. A. Costa
1
, Maria L. Corradi da Silva
4
, Johannes A. van Veen
1
, Eliana G. M. Lemos
2
&
Eiko E. Kuramae
1
Acidobacteria have been described as one of the most abundant and ubiquitous bacterial phyla in soil.
However, factors contributing to this ecological success are not well elucidated mainly due to diculties
in bacterial isolation. Acidobacteria may be able to survive for long periods in soil due to protection
provided by secreted extracellular polymeric substances that include exopolysaccharides (EPSs).
Here we present the rst study to characterize EPSs derived from two strains of Acidobacteria from
subdivision 1 belonging to Granulicella sp. EPS are unique heteropolysaccharides containing mannose,
glucose, galactose and xylose as major components, and are modied with carboxyl and methoxyl
functional groups that we characterized by Fourier transform infrared (FTIR) spectroscopy. Both
EPS compounds we identied can eciently emulsify various oils (sunower seed, diesel, and liquid
paran) and hydrocarbons (toluene and hexane). Moreover, the emulsions are more thermostable over
time than those of commercialized xanthan. Acidobacterial EPS can now be explored as a source of
biopolymers that may be attractive and valuable for industrial applications due to their natural origin,
sustainability, biodegradability and low toxicity.
Acidobacteria is a very abundant and ubiquitous bacterial phylum in natural ecosystems
1–4
. It has been suggested
that exopolysaccharide (EPS)-producing bacteria may be able to survive for long periods in soil due to protective
properties of EPS. e dominance of Acidobacteria in acidic environments and chemically polluted sites (e.g.
where heavy metal
5–7
, petroleum compounds
8
, linear alkylbenzene sulfonate
9
and p-nitrophenol
10
are major con-
taminants) is related to the ability of these bacteria to produce large amounts of EPS.
e ability to synthesize EPS has been previously reported for some members of the Acidobacteria phylum.
ese reports include genome mining studies
11
, description of cultured Acidobacteria species
12,13
and their
interactions with plants
14
. However, EPS was never isolated and characterized in these studies. It was suggested
that EPS may provide protection against environmental stress and enable bacterial survival under unfavourable
soil conditions, since Acidobacteria are abundant
15
. e potential importance of EPS in soil is great - it may be
involved in the formation of soil matrix, serve to sequester water and nutrition, and be involved in bacterial
cell-surface adherence and soil aggregate formation
12
. ese hypotheses have not yet been conrmed by func-
tional studies and such functions may overlap with general biological and ecological functions that are protective
in nature for Acidobacteria.
e ability to synthesize EPS and secrete it into the environment as soluble (slime) or insoluble (capsular)
polymers is quite common among bacteria
16
. However, EPSs produced by various bacteria vary in molecular
weight, composition and physicochemical properties that include gelling, emulsifying, stabilizing, thickening,
1
Netherlands Institute of Ecology (NIOO-KNAW), Department of Microbial Ecology, P.O. Box 50, 6700 AB,
Wageningen, the Netherlands.
2
São Paulo State University (Unesp), School of Agricultural and Veterinarian Sciences,
Rod. Prof. Paulo Donato Castellane km 5, CEP 14884-900, Jaboticabal, Brazil.
3
Embrapa Instrumentação, Rua XV de
Novembro, 1452, CEP 13560-970, São Carlos, Brazil.
4
Faculdade de Ciências e Tecnologia (Unesp), Departmento de
Química e Bioquímica, Rua Roberto Símonsen, 305, CEP 19060-900, Presidente Prudente, Brazil.
*
These authors
contributed equally to this work. Correspondence and requests for materials should be addressed to E.E.K. (email:
e.kuramae@nioo.knaw.nl)
Received: 17 October 2016
Accepted: 15 December 2016
Published: 24 January 2017
OPEN
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Scientific RepoRts | 7:41193 | DOI: 10.1038/srep41193
suspending, coagulating and texture-enhancing. ough, only few of these bacterial products (e.g. alginate, dex-
tran, gellan gum, xanthan) have been successfully commercialized.
Biopolymers including novel microbial-derived EPSs are very attractive for the industrial sector due to their
natural origins, sustainability, biodegradability and general low toxicity
17
. Industrial applications of microbial
EPSs have been extensively reviewed
17–23
. e broad spectrum of applications for EPSs range from human health,
to food and fodder production, to chemical industry and environmental technologies (e.g. bioremediation and
phytoremediation).
In the food industry, EPSs are used as thickening, gelling and suspending agents. For example, xanthan (from
Xanthomonas campestris) is used as food additive
16
(European Union Food Safety Authority, food additive E415).
e EPSs also have the properties as bioemulsiers that are used in the cosmetic and chemical (e.g. pesticide)
industries and for bioremediation of soils and water by enhancing oil and heavy metal recovery
24
.
In light of the major absence of published reports on acidobacterial EPS, the aim of the present study was
to gain insights into the physicochemical nature of EPS polymers produced by two genetically closely related
Acidobacteria strains belonging to Granulicella sp., which genomes are not sequenced. Moreover, this research
focused on the capacity of these EPSs on emulsion formation and stability, which are important properties for
industrial and ecological applications.
Results and discussion
EPS production by acidobacterial isolates. Dierent bacterial species produce dierent extracellular
matrices in dierent bacterial growth phases. For example, cellulose, gellan and alginate are exclusively produced
by Azotobacter vinelandii during the exponential growth phase, curdlan by Alcaligenes faecalis during the decel-
eration growth phase, xanthan by Xanthomonas campestris during the exponential and stationary phases
25,26
,
and EPSs are produced by Alteromonas macleodii from the end of the exponential phase through the stationary
phase
27
. In the present study, the yield of EPS produced by Granulicella spp. WH15 and 5B5 strains increases in
the late growth stage (data not shown). e EPS yield was much greater on solid medium than in liquid culture.
erefore, the h day of bacterial growth on solid medium was selected for EPS extraction from both bac-
terial strains. Strain WH15 showed greater production of EPS than strain 5B5 under experimental conditions
(90 mm-diameter Petri dish): 36.95 mg (dry weight) and 9.56 mg per plate, respectively. Dierent yields of EPS
from closely related isolates belonging to the same genus have also been reported for various bacterial taxonomic
groups (e.g. Rhizobium
28
, Halomonas
29
and Xanthomonas
30
).
Both acidobacterial exopolysaccharides were soluble in water and insoluble and stable in all tested organic
solvents (chloroform, methanol and toluene).
EPS Component Analysis. Bacterial extracellular matrix chiey consists of polysaccharides. Other com-
pounds including proteins, nucleic acids, lipids and humic acids comprise up to 40% of EPS content
31
. However,
in this study our main interest was on carbohydrates, therefore we focused on the major carbohydrate fraction of
acidobacterial EPS aer removing insoluble particles by downstream extraction processes.
A robust and simple extraction method
32
allowed us to isolate and purify EPS from acidobacterial cul-
tures. is resulted in high quality extracts with very low amounts of proteins. We refer to EPS produced by
Granulicella sp. strains WH15 and 5B5 as EPSWH15 and EPS5B5, respectively. No protein was detected in
EPSWH15, whereas the protein content in EPS5B5 was not signicant (< 0.01% (w/w) protein relative to total
EPS extract). e two EPS preparations diered slightly in total carbohydrate content: 43.5% ± 3.9% (s.d.) for
EPSWH15 and 41.8% ± 2.0% for EPS5B5. However, this dierence is not statistically signicant (p > 0.05). e
fractional carbohydrate composition of our EPS extracts was considerably greater than that previously reported
for a Pseudomonas sp. (33.81%) content
33
. It has been suggested that the dierences in determined carbohydrate
mass might be attributed to residual water of hydration as EPS extract is composed of 99% water
34,35
.
Structural analysis of EPS - molecular weight, compositional homogeneity and monomeric
composition. e size homogeneities and molecular weights of acidobacterial EPSWH15 and EPS5B5 were
determined using high-performance size-exclusion chromatography (HPSEC) and (Fig.S1). e molecular
weights were estimated to be greater than 1.4 × 10
6
Da according to a standard calibration curve obtained for
various molecular weight dextran standards. e degree of polydispersity (currently dened by the IUPAC as
dispersity, D
M
= M
w
/M
n
, where M
w
is the weight-average molar mass and M
n
is the number-average molar mass)
was 1.4 and 1.3 for EPSWH15 and EPS5B5, respectively, suggesting relatively uniform dispersity (homogeneous
size distribution).
We determined the monomeric saccharide composition for the exopolysaccharides aer acid hydrolysis
(Table1). Both EPSs were identied as heteropolysaccharides containing mannose (Man), glucose (Glc), galac-
tose (Gal) and xylose (Xyl) as major components in relative molar proportions of 1.0/1.3/2.5/4.1 (Man/Glc/Gal/
Xyl) for EPSWH15 and 1.0/0.1/0.6/0.3 for EPS5B5. Additionally, rhamnose (Rha), glucuronic (GlcA) and galac-
turonic (GalA) acids were identied as minor components of EPSWH15, whereas EPS5B5 contained slightly
more Rha than Glc, GlcA was a minor component and GalA was absent to the limit of measurement sensitivity
(Table1). However, the quantities of GlcA and GalA might be underestimated due to the hydrolyses conditions
used in this study, which are ecient for hexoses, pentoses and deoxy sugars but not ideal for uronic acids. e
monosaccharide compositions we determined for EPSWH15 and EPS5B5 are in basic agreement with previously
published observations
36
since mannose (Man), glucose (Glc), galactose (Gal) and xylose (Xyl) are among the
most common monosaccharides found in EPS
37,38
.
Having experimentally determined the monomeric saccharide compositions and the mean molecular masses
of EPSWH15 and EPS5B5, and having additionally determined that their measured dispersities suggest rela-
tively homogeneous size distributions, we roughly model the number of constituent monomer units of each
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Scientific RepoRts | 7:41193 | DOI: 10.1038/srep41193
monosaccharide type for each monomeric EPS molecule. Accordingly, for ~1.4 kDa sized EPS monomers,
EPSWH15 is expected to be comprised of 86 Man, 114 Glc, 219 Gal, 351 Xyl, 1 Rha, 68 GlcA and 1 GalA monosac-
charides (Fig.1). EPS5B5 is expected to be comprised of 387 Man, 33 Glc, 214 Gal, 115 Xyl, 40 Rha, 12 GlcA and
no GalA monosaccharides. us, while both EPSs contain roughly equal amounts of Gal, EPSWH15 is enriched
~3-fold for Xyl relative to EPS5B5, while EPS5B5 is enriched ~4-fold for Man relative to EPSWH15. Of the mon-
osaccharide types occurring in relatively lower abundances for both EPSs, EPSWH15 is enriched ~3-fold for Gal
and ~5.7-fold for GlcA relative to EPS5B5, whereas EPS5B5 is enriched ~40-fold for Rha relative to EPSWH15.
Additionally, only EPSWH15 was found to contain detectable GalA (~1 monosaccharide per 1.4 kDa mono-
mer). Interestingly, Xyl is common in eukaryotic polysaccharides, but less commonly occurring in bacteria
39
.
Xyl was previously identied, for example, in EPSs of Zoogloea sp.
40
, Myxococcus xanthus, Pseudomonas solan-
acearum
41
, Alteromonas hispanica
39
and Acidithiobacillus ferrooxidans
42
.
FTIR spectral analysis of EPS functional groups. Chemical composition, type of glycosides link-
age and branching of polysaccharides are factors that aect the overall structure of polysaccharides. In addi-
tion to structure, these factors determine the physicochemical properties of polysaccharides, which together
with 3-dimensional structure impact physiological functions
16
. Infrared (IR) spectroscopy by Attenuated Total
Reectance (ATR) allows the identication of molecular bonds by measuring the absorption of light at a given
wavelength (λ ) or wave number (1/λ ). We collected ATR-FTIR spectra of EPSWH15 and EPS5B5 (Fig.S2). Both
EPSs showed strong absorption bands in the range of 4000 to 400 cm
−1
. e spectra between 3600 to 3200 cm
−1
of EPSWH15 and EPS5B5 indicate to stretching vibration of O-H
43
. e absorption peak from 3000 cm
−1
to
2900 cm
−1
is attributed to the C-H stretching and bending vibrations
44
. e peaks in the range between 1640
to 1550 cm
−1
and 1460 to 1400 cm
−1
are absorption bands of carboxylate groups, including a set of strong C-O
stretching bands at 1456 and 1450 cm
−1
. In this case, the peak can be also attributed to stretching of the carbox-
ylate functional group (COO-), consistent with the EPSs being acidic polysaccharides. In the ATR-FTIR spectra
of EPSWH15 and EPS5B5, there were also signals characterizing unionized carboxylic groups and bands for
Exopolysaccharide
Man Glc Gal Xyl Rha GlcA GalA
mean ± SD (%)
a
EPSWH15 (Rel. abundance)
b
10.25 ± 0.02
(1.000)
13.55 ± 0.08
(1.322)
26.12 ± 0.06
(2.548)
41.81 ± 0.03
(4.079)
0.065 ± 0.01
(0.006)
8.09 ± 0.09
(0.789)
0.085 ± 0.02
(0.008)
EPS5B5 (Rel. abundance)
b
47.85 ± 0.06
(1.000)
4.01 ± 0.05
(0.084)
26.45 ± 0.09
(0.553)
14.14 ± 0.09
(0.296)
4.93 ± 0.08
(0.103)
1.50 ± 0.04
(0.031)
*
(*)
Table 1. Monosaccharide composition of the exopolysaccharides EPSWH15 and EPS5B5 produced by
Acidobacteria WHT15 and 5B5 strains, respectively.
a
For n = 3 biological replicates.
b
For each EPS, numbers
in parentheses are relative abundances for each monosaccharide relative to mannose. Man, mannose; Rha,
rhamnose; GlcA, glucuronic acid; GalA, galacturonic acid; Glc, glucose; Gal, galactose; Xyl, xylose;
*, undetected at a sensitivity limit of 0.001%.
Figure 1. Monosaccharide composition of EPSWH15 (black lled bars) and EPS5B5 (white lled bars)
modelled using experimentally measured EPS monomer masses (Mw) and relative monosaccharide
abundances determined in the present study. Monosaccharide types: mannose, Man; glucose, Glc; galactose,
Gal; xylose, Xyl; rhamnose, Rha; glucuronic acid, GlcA; galacturonic acid, GlaA. For each ~1.4 MDa sized EPS,
the approximate number of monosaccharides for each monosaccharide type was calculated according to the
equation: 1,400,000 (Da) ≤ n[Σ (Mi)(ai)], where n is an integer multiplicative factor (the independent variable),
and Mi and ai are the molecular mass and experimentally determined relative abundance, respectively, for each
monosaccharide type i.
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the respective O–H stretching at 1641 and 1658 cm
−1
, respectively. In the ATR-FTIR spectra of EPS5B5, there
were no peaks around 1740 cm
−1
, which are attributed to C = O stretching of carbonyls in esters. In contrast, for
EPSWH15, there is a very low band intensity at 1766 cm
−1
corresponding to C = O stretching of carbonyls in
esters (Fig.S2a).
Other signals at 1100 and 1050 cm
−1
indicate glucopyranosyl residues. A complex sequence of peaks are
observed in the region from 1200 to 800 cm
−1
, due in part to C-O-C, C-O, ring-stretching vibrations of polysac-
charides
45
. is spectral domain is considered the ngerprint region of EPS, and can be used to assign α and β
glycosidic linkages. Both EPSs showed bands at ~820 cm
−1
and ~890 cm
−1
, characteristic of α and β glycosidic
linkages, respectively.
Nuclear magnetic resonance (NMR) spectroscopy analysis of EPS. We conducted
1
H NMR and
13
C
NMR studies in order to conrm the presence of functional groups and monosaccharide constituents for both
EPSs (Fig.S3). Hydrolysates of EPSs produced by both Granulicella strains were rst analysed by
1
H NMR spec-
troscopy. e
1
H NMR spectrum of the EPS showed the presence of pyruvate groups as revealed by resonances
at 2.22 ppm. Presence of ketal-linked pyruvate and glucuronic acid or galacturonic acid has been reported to be
responsible for the polyanionic nature of the exopolysaccharides
17
. Additionally, this spectrum showed some
proton resonances belonging to CH
2
or CH
3
groups. In FigureS3a, all of the signals in the
1
H NMR spectra could
be assigned to the various constituent monosaccharides, including glucose, rhamnose, mannose, galactose, and
xylose, conrming that the EPSs are acidic heteropolysaccharides.
1
H NMR and
13
C NMR spectra taken together
led us to conclude the absence of acetate groups (Fig.S3a,S3b).
e
13
C NMR spectra (Fig.S3b) from 5B5 (Fig.S3b1) and WH15 (Fig.S3b2) showed four specic regions
corresponding to carbohydrates. e signals at high eld around 20 ppm indicate the presence of a methyl group
from rhamnose, a deoxy sugar, and from pyruvic acid. Two bands of more intense signals in the region of ano-
meric carbons at 98 and 104 ppm indicate, respectively, monomer units involved in α and β glycosidic linkages.
ese data conrm our conclusions from the ATR-FTIR analysis. Signals in low eld, around 172 ppm, can be
attributed to carboxyl groups present in uronic (glucuronic and galacturonic) and pyruvic acids. e region
between 60 to 77 ppm corresponds to other carbons (C-6, C-5, C-4, C-3 and C-2) from the monosaccharides
units, that, when involved in glycosidic linkages, are shied down eld (~79–84 ppm).
In summary, according to these spectroscopic chemical characterizations, the organization of these groups
appears to be associated with emulsication properties of acidobacterial EPSs produced by WH15 and 5B5
strains. Additionally, these observations are in agreement with our previous results of EPS monomer character-
ization (Table1).
Rheological properties. EPS viscosity is an important parameter for industry applications. e rheolog-
ical prole of EPSWH15 and EPS5B5 water solutions (10 g·L
−1
) are presented in Fig.2. Both solutions showed
non-Newtonian behaviour. e viscosities of both solutions at shear rate of 25 s
−1
at 25 °C were low, with 31.1 and
7.1 mPa·s for EPSWH15 and EPS5B5, respectively. e viscosities of both acidobacterial EPSs decreased as shear
rate increased to slightly thixotropic behaviour. Viscosity of the samples was also time dependent, increasing
with commencement of mechanical stress and decreasing at the end of the process. us, viscosity tests were per-
formed versus time at constant shear rate. At a shear rate of 10 s
−1
, the apparent viscosities of 1% (w/v) solutions
of EPSWH15 and EPS5B5 were low, conrming the overall low viscosity of the samples (data not shown). e
solutions may undergo physical or chemical changes such as gelation during the ow. An example of EPS as a
pseudoplastic type of uid with thixotropic behaviour was previously reported
46
for 0.25% (w/v) Rhizobium EPS
solution.
e values of the power-law parameters of both EPSs obtained by linear regression are shown in Table2. As
n tends to 1, the shear-thinning properties become less pronounced, so that Newtonian behaviour is achieved
when n = 1. In any case, all dispersions characterized did not exhibit a marked shear-thinning response (n > 0.5).
However, the acidobacterial EPSs showed lower consistency coefficients when compared to xanthan gum
(2.96 ± 0.035).
Figure 2. Rheological prole of acidobacterial exopolysaccharide solutions (10 g·L
−1
) (a) EPSWH15 and (b)
EPS5B5. e ow curves were measured at 25 °C. e ▪ and ⦁ symbols represent η (Pa·s) and t (Pa) at 10 g·L
−1
,
respectively.
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Emulsifying activity. e ability of EPS to emulsify lipids is a desired property with potential industrial and
ecological applications. e commercial usage of EPS includes its application as an emulsion-forming agent (e.g.
for bioremediation of oil polluted soil and water, food and cosmetic applications, agrochemicals), or as a stabi-
lizer (e.g. for the food industry). erefore, we compared the emulsifying ability of acidobacterial EPSWH15 and
EPS5B5 with the synthetic surfactants Tween 80 and xanthan (a successfully commercialized and widely used
EPS).
Emulsication indices measured for EPSWH15 and EPS5B5 emulsions in the presence of various oils and
hydrocarbons are shown in Table3. Both EPSWH15 and EPS5B5 showed bioemulsication ability by forming
stable emulsions with hydrocarbon mixtures (diesel and liquid paran oil) and vegetable oil (sunower seed oil)
as well as with aliphatic (n-hexane) and aromatic (toluene) hydrocarbons.
Both acidobacterial EPSs (EPSWH15 and EPS5B5) showed higher E
24
values for sunower seeds (66.98 and
67.89%, respectively) and liquid paran oils (58.71 and 54.18%, respectively) (Table3). Acidobacaterial EPSs
emulsication ability for sunower seeds oil was higher than that of xanthan. However, synthetic surfactant
Tween 80 was more ecient than acidobacterial EPSs and xanthan gum, with emulsication eciencies of 100%
against sunower seed oil and 91.35% against liquid paran oil.
e lowest activity was observed for emulsication of toluene, for both acidobacterial EPS (values between
10.00% and 21.30%), xanthan (38.26%) and synthetic surfactant Tween 80 (46.00%). All emulsions were sta-
ble at 30 °C during 7 and 15 days of incubation. No sedimentation, occulation or coalescence of emulsions
was observed. Moreover, EPSWH15 and EPS5B5 emulsions in the presence of sunower and paran liquid oils
remained stable for three months, showing no sign of droplet coalescence aer standing at room temperature
(30 °C) (data not shown). Emulsifying and surfactant activities together have been previously described as impor-
tant functional properties of bacterial exopolymers
47
.
Interestingly, EPS5B5 gave overall better or comparable E values compared to those obtained from EPSWH15.
The major differences were observed for emulsification of hexane and diesel oil. Emulsification of hexane
is important for the industrial water waste treatment, while diesel emulsication may be applied in oil and
oil-related product removal from the environment. In this sense, diesel oil serves as a model agent/substrate for
studying hydrocarbon biodegradation. It is comprised of a variety of molecules: paran, olens, naphtha and
aromatic compounds. Moreover, diesel engines are dominating engines in the transportation sector, which is
linked to increase of pollution emission. e mixture of diesel fuel, water, and other additives reduces emissions
of particulate matters and smoke as well as NOx and CO
2
.
An emulsion is a macroscopic dispersion of two liquids, in which one compound is a continuous part dis-
persed throughout small drops of the other. Among other characteristics, rheological properties, physical sta-
bility, coalescence, sedimentation, and the appearance of emulsions depend on the size and size distribution of
droplets. erefore, the size and homogeneity of emulsion droplets are important criteria for EPS industrial appli-
cation. e method applied in the current study enable measurement of droplet sizes ranging from 0.02–2000 µ m.
e results showed that EPSWH15 and EPS5B5 produced emulsions with diesel, sunower and liquid paran
oils with quite small and uniform drops of oil phase (~100 µ m) (Fig.3). However, the same EPSs in the presence
of hexane and toluene showed droplets of 40 µ m diameter.
e eect of acidobacterial EPS concentration on emulsion stability was studied for liquid paran oil. For
EPSWH15, we observed a trend of increased emulsifying activity with increased polymer concentration (Fig.4).
However, those changes were not signicant. EPS5B5 showed the best emulsifying activity at a concentration of
1.5 g·L
−1
. For the remaining tested concentrations, the emulsifying indexes (E) were slightly lower with no signif-
icant dierences between EPS concentrations.
e stability of the EPS solutions (0; 0.5; 1.0; 1.5 and 2.0 g·L
−1
), as bioemulsiers at temperatures of 70 °C
and 90 °C for 50 min, showed that heat treatment did not reduce the emulsion forming capacity of either EPS
in the presence of liquid paran oil (Fig.4). us, the acidobacterial EPSs are thermostable as bioemulsiers.
However, most of the microbial EPSs described in the literature are not thermostable, except alasan produced by
Acinetobacter radioresistens KA53
48
. e high stability of both EPSWH15 and EPS5B5 with regard to temper-
ature and time exposure clearly demonstrate their potential for applications involving extreme environmental
conditions.
Conclusions
In this study, the acidobacterial EPSs of WH15 and 5B5 strains belonging to Granulicella sp. were characterized.
e EPS of WH15 and EPS of 5B5 strains, named EPSWH15 and EPS5B5, respectively, were characterized as
heteropolysaccharides containing mannose, glucose, galactose and xylose as the major monosaccharide com-
ponents. Furthermore, the EPSs had better bioemulsier properties than xanthan. e high stability of the both
EPSs regarding temperature and time exposure clearly demonstrates their potential for applications in extreme
environmental conditions.
Type of exopolysaccharide K η
Xanthan 2.96 ± 0.035 0.22 ± 0.07
EPSWHT15 0.06 ± 0.002 0.82 ± 0.08
EPS5B5 0.03 ± 0.001 0.57 ± 0.04
Table 2. Coecients of the power law model for acidobacterial EPSWH15 and EPS5B5 solutions
(10 g·L
−1
). Mean values ( ± standard deviation); n = Flow behavior index; K = consistency coecient obtained
by the Ostwald-de Waele model: η = Kγ
(n−1)
.