J. Orehek et al. / Carbohydrate Polymers 113 (2014) 16–21
17
Table 1
of NaOH pellets by continuous mixing for 30 min. The remaining
pellets of NaOH were removed before filtration of neutralized
product. After neutralization the TsCMC was washed three times
Results of CHSP elemental mass analysis and theoretically calculated elemental
composition of CMC and TsCMC.
◦
Element (%)
CMCt
CMCd
TsCMCt
TsCMCd
with absolute EtOH and dried at 45 C to a constant mass.
C
H
S
40.5
4.9
0
38.8
5.0
<0.02
<0.02
38.9
4.6
1.3
38.5
5.0
1.5
2
.2. Physicochemical characterization of TsCMC
P
0
1.24
0.8
Viscosity was measured on an Anton Paar Physica MCR 301 rota-
Legend: CMCt = theoretical elemental mass composition calculated for CMC with
DS value of 0.7; CMCd = experimentally determined elemental composition;
TsCMCt = theoretically calculated elemental composition for TsCMC with DS of
carboxymethylic groups 0.7 and DS of tosylic groups 0.1 in the presence of
one molecule of Na3PO4 per 10-anhydroglucosic units present as an impurity;
TsCMCd = experimentally determined elemental composition. For theoretical cal-
culations of element compositions it has been assumed that DS of parental CMC
tional plate–plate system with a plate diameter of 49.98 mm. The
distance between plates was 0.25 mm and the measuring temper-
◦
ature was (25.00 ± 0.01) C. Approximately 490 L of sample was
applied to fill the gap between the plates. Flow curves in a shear rate
−
1
ranging from 10 to 1000 s were measured in 29 steps with a time
delay of 5 s between successive measurements. The results for vis-
(
DS = 0.7) did not change during derivatization and that all carboxylic groups are
−
1
cosity measurements are reported at a shear rate of 1000 s . The
intrinsic viscosities were determined by measuring the viscosity of
diluted samples. Samples were diluted in BHM or pure water to a
final concentration of 0.05, 0.1, 0.2 and 0.3% (w/v) CMC or TsCMC.
The intrinsic viscosity was determined by graphically evaluating
the limit of the following equation:
present as Na-salts.
1
5 min. After the incubation and colour development, the samples
were cooled to room temperature in a water bath. Absorbance at
75 nm was measured and the reducing sugar concentration was
5
determined from a calibration curve, which was freshly prepared
from standard glucose solutions (0–5 mM). Biodegradability of
TsCMC and other tested cellulose based thickeners was tested
on a modified Buschnell Hass growth media (BHM) (Bushnell &
Haas, 1941). The modified BHM growth media differs from the
original formulation due to the elimination of iron source, which
was shown to cause aggregation of CMC. The overnight bacterial
culture was washed two times with a sterile physiological solution
and 1 mL was inoculated into 100 mL of BHM growth medium.
ꢀ
− ꢀ
0
[
ꢀ] = lim
(1)
ꢁ
→0 ꢀ0ꢁ
where [ꢀ] is the intrinsic viscosity, ꢀ viscosity of diluted polymer
solution, ꢀ viscosity of solvent in the absence of solute, and ꢁ mass
0
3
concentration of solute in g/cm .
IR spectra were recorded on Perkin Elmer Spectrum 100 FTIR
spectrophotometer with diffused reflection technique as described
previously (Sherman Hsu, 1997).
Elemental analysis of TsCMC was performed according to the
following standardized methods: SIST EN 13137 for the determina-
tion of total organic carbon (TOC) in waste, sludges and sediments,
SIST ISO 609 for hydrogen determination with high temperature
combustion method, SIST ISO 351 for determination of total sul-
fur with high temperature combustion method, and ISO 6878 for
determination of phosphorus with ammonium molybdate spectro-
metric method. The samples for the determination of phosphorous
were prepared according to SIST EN 13346—determination of trace
elements and phosphorus with aqua regia extraction methods.
For evaluation of emulsifying efficiency solutions of 5 mg CMC
or TsCMC in 9 mL of demineralized water were prepared. To these
solutions 1 mL of paraffin oil stained with lysochrome Sudan III was
added. Emulsions were prepared by hand shaking of closed tubes
for 1 min. The evaluations of emulsion stability was performed
after 1 h, one day and one week following emulsion preparation
2.4. Biodeterioration of TsCMC
The biodeterioration of TsCMC defined as a process of any
undesirable change in the properties of materials caused by orga-
nisms was measured as the decrease in viscosity of the growth
medium and was tested with cultures of Bacillus firmus, Bacil-
lus mycoides, Salmonella typhimurium, Azospirillum brasilense ATCC
29145, Alcaligenes sp. NCIB 11015, Bacillus subtilis JH 642, Strepto-
myces coelicolor DSM 40233, B. subtilis NCIB 3610, B. subtilis IS-75,
Chromobacterium violaceum, Cellulomonas uda DSM 20108. All inoc-
◦
ulated samples were aerobically incubated at 37 C in the dark
on an orbital shaker (200 rpm) for one week. The biodeteriora-
tion of TsCMC or other commercial cellulose based thickeners was
estimated as a fraction of residual viscosity remained after the incu-
bation (initial viscosity − final viscosity) × 100.
(Sroková, Tomanová, Ebringerová, Malovíková, & Heinze, 2004).
The dynamic contact angle measurements were performed on
3. Results and discussion
FIBRO DAT 1100 Dynamic Absorption Tester. A testing surface was
prepared by soaking filter paper with 1% (w/v) water solution of
CMC or TsCMC and dried at 45 C over two days. 6 L drops of
3.1. Chemical characterization
◦
water solution were placed on the testing surface and contact angle
between the basis and water drops was recorded over a period of
To the best of our knowledge, the tosylation via ester linkage
to CMC has not been performed yet. As given in Fig. 1, the FTIR
spectra indicate that global vibrational structures of parental CMC
and derived TsCMC are similar. The two spectra, however, differ at
several vibrational bands, which were broadened and shifted. Most
5
0 s.
2.3. Biodegradation of TsCMC
−
1
notably the bands at 816 and 690 cm were present only in TsCMC
but not in CMC. The two vibrations correspond to out of plane C
The biodegradation of TsCMC used as a sole carbon source was
H
measured as an increase in reducing sugar concentration during
the incubation, by increase in optical density (OD650), and an
increase of bacterial colony forming units during the incubation.
Reducing sugar concentrations were determined spectrophoto-
metricaly using DNS reagent (Miller, 1959). DNS reagent was
prepared as a solution of 10 g 3,5-dinitrosalicylic acid and 300 g
of K, Na-tartrate in 1 L of 0.4 M NaOH. Next 1 mL of DNS reagent
was added to 1 mL of sample or standard glucose solution. The
deformation and out of plane ring vibrations of p-toluenesulphonic
acid, respectively. This suggests that CMC has been tosylated. The
element composition of TsCMC is given in Table 1. The TsCMC
contained 1.3% sulfur, which allowed calculation of the average
degree of substitution of CMC with tosylic groups. On average every
tenth anhydroglucose unit of CMC was substituted with tosyl group
(DS = 0.1). The results suggest that TsCMC contained few phospho-
rous impurities, which was likely a result of P O hydrolysis to
4
10
◦
reaction was carried out in glass tubes incubated at 100 C for
Na PO4 during the TsCMC synthesis and purification.
3