Combination Of Acid Treatment Research Articles

Combination of acid treatment and dual network fabrication to stretchable cellulose based hydrogels with tunable properties

Cellulose based hydrogels with a relatively high stretchability were fabricated in the NaOH/urea system via sequential chemical crosslinking and dual network fabrication. The first step involved crosslinking of cellulose using epichlorohydrin as a crosslinker. Cryo-electron microscopy analysis revealed the utilization of diluted acid to treat hydrogels significantly affected the morphology of the first network and improved the mechanical properties. After diffusion of precursors into the first network, the dual network hydrogels were generated after the UV light-initiated polymerization. Raman spectroscopy demonstrated a spatial distribution of second networks within the first network. The compression strength of hydrogels synthesized under the optimized conditions was effectively enhanced from 0.04 MPa to 10.9 MPa. In addition, the tensile properties of hydrogels were easily adjusted via copolymerization of acrylic acid with acrylamide. The highest strain could reach 219.5% with a tensile strength of 1.4 MPa. This work provides a promising and simple strategy to develop a cellulose based hydrogel with enhanced and tunable mechanical properties for wide applications.

Effects of Limited Hydrolysis and High-Pressure Homogenization on Functional Properties of Oyster Protein Isolates

In this study, the effects of limited hydrolysis and/or high-pressure homogenization (HPH) treatment in acid conditions on the functional properties of oyster protein isolates (OPI) were studied. Protein solubility, surface hydrophobicity, particle size distribution, zeta potential, foaming, and emulsifying properties were evaluated. The results showed that acid treatment led to the dissociation and unfolding of OPI. Subsequent treatment such as limited proteolysis, HPH, and their combination remarkably improved the functional properties of OPI. Acid treatment produced flexible aggregates, as well as reduced particle size and solubility. On the contrary, limited hydrolysis increased the solubility of OPI. Furthermore, HPH enhanced the effectiveness of the above treatments. The emulsifying and foaming properties of acid- or hydrolysis-treated OPI significantly improved. In conclusion, a combination of acid treatment, limited proteolysis, and HPH improved the functional properties of OPI. The improvements in the functional properties of OPI could potentiate the use of oyster protein and its hydrolysates in the food industry.

Observation of the intrinsic magnetic susceptibility of highly purified single-wall carbon nanotubes

We report the observation of the intrinsic magnetic susceptibility of highly purified SWCNT samples prepared by a combination of acid treatment and density gradient ultracentrifugation (DGU). We observed that the diamagnetic susceptibility of SWCNTs increases linearly with increasing nanotube diameter. We found that the magnetic susceptibility divided by the diameter is a universal function of the scaled temperature. Furthermore, the estimated magnetic susceptibilities of pure semiconducting and pure metallic SWCNT samples suggest that they respond differently to changes in carrier density, which is consistent with theory. These findings provide experimental verification of the theoretically predicted diameter, temperature, and metallicity dependence of the magnetic susceptibility.

Extraction and Characterization of Cellulose Nanofibers from Phyllostachys nidularia Munro via a Combination of Acid Treatment and Ultrasonication

In this work, α-cellulose was extracted from Phyllostachys nidularia Munro using an acidified sodium chlorite treatment followed by alkali treatments, and cellulose nanofibers (CNFs) were then extracted from α-cellulose via the combination of sulfuric acid (64 wt%) and low-intensity ultrasonication. The results showed that superior CNFs were successfully extracted and their diameters were in the range of 5 to 20 nm. Fourier transform infrared spectroscopy (FTIR) suggested that a majority of the hemicellulose and lignin were removed from the original material and that the chemical constituents of α-cellulose and CNFs were similar. X-ray diffraction (XRD) analysis indicated that the relative crystallinity of CNFs was significantly increased to approximately 69.32% and all specimens presented a typical cellulose I crystal form. Thermogravimetric analysis (TGA) showed that the thermostability of the CNFs was greatly increased.

Nanocapsules of a cationic polyelectrolyte and nucleic acid for efficient cellular uptake and gene transfer.

Polyelectrolyte nanocapsules, consisting of poly(allylamine hydrochloride) (PAH) and a nucleic acid, i.e. either DNA or siRNA, were prepared with calcium phosphate nanoparticles as template. This inorganic core was removed by a combination of acid treatment and dialysis, leading to capsules with a diameter of about 140 nm. These capsules were well taken up by HeLa cells and led to an efficient gene transfer, i.e. transfection by DNA and gene silencing by siRNA. They behaved clearly different from unstructured aggregates of DNA and PAH, i.e. polyplexes, underscoring the effect of their internal structure.

Isolation of Shiga Toxin–Producing Escherichia coli Serogroups O26, O45, O103, O111, O121, and O145 from Ground Beef Using Modified Rainbow Agar and Post–Immunomagnetic Separation Acid Treatment

It is estimated that at least 70% of human illnesses due to non-O157 Shiga toxin-producing Escherichia coli (STEC) in the United States are caused by strains from the top six serogroups (O26, O45, O103, O111, O121, and O145). Procedures for isolating STEC from food products often use plating media that include antimicrobial supplements at concentrations that inhibit background microflora growth but can also inhibit target STEC growth. In this study, an agar medium with lower supplement concentrations, modified Rainbow agar (mRBA), was evaluated for recovery of STEC serogroups O26, O45, O103, O111, O121, and O145 from ground beef enrichments. A post-immunomagnetic separation (IMS) acid treatment step was additionally used to reduce background microflora and increase recovery of target STEC strains. Ground beef samples (325 g) were artificially contaminated with STEC and confounding organisms and enriched for 15 h. Recovery of the target STEC was attempted on the enrichments using IMS and plating onto mRBA and Rainbow agar (RBA). Additionally, acid treatment was performed on the post-IMS eluate followed by plating onto mRBA. Using the combination of mRBA and acid treatment, target STEC were isolated from 103 (85.8%) of 120 of the low-inoculated samples (1 to 5 CFU/325-g sample) compared with 68 (56.7%) of 120 using no acid treatment and plating onto RBA with higher levels of novobiocin and potassium tellurite. The combination of acid treatment and mRBA provides a significant improvement over the use of RBA for isolation of STEC serogroups O26, O45, O103, O111, O121, and O145 from raw ground beef.

An investigation into cyclohexanone ammoximation over Ti-MWW in a continuous slurry reactor

In the present study, the liquid-phase ammoximation of cyclohexanone with ammonia and hydrogen peroxide was studied using a MWW-type titanosilicate (Ti-MWW) catalyst in a continuous slurry reactor to develop a clean process for producing cyclohexanone oxime. The reaction parameters, which governed the cyclohexanone conversion, oxime selectivity and catalyst deactivation, were investigated by simulating the operating conditions of an industrial process. Under optimized reaction conditions, Ti-MWW produced a cyclohexanone conversion and oxime selectivity over 96% and 99%, respectively. Moreover, Ti-MWW was extremely robust and showed a longer lifetime than the conventional titanium silicalite-1 catalyst. The causes of deactivation were elucidated to be the coke deposition and partial dissolution of the zeolite framework of Ti-MWW during ammoximation. The deactivated Ti-MWW catalyst was regenerated effectively by a combination of acid treatment and cyclic amine-assisted structural rearrangement.

Effects of chemical treatments on thermal expansion properties of cordierite ceramics

Cordierite honeycomb ceramics was treated with 1.5 M HNO3, followed with 1.5 M NaOH at 93°C. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal expansion (CTE) caused by heat treatment, a phenomenon observed in samples treated solely with acid. Inductively coupled plasma (ICP) analysis results reveal that the alkali treatment preferentially dissolved “free” SiO2 left in the acid-treated samples, which is considered to be a key factor responsible for the CTE rebounding.

Study of lysosomal enzymes in fish muscle tissue - X. Purification of a pepstatin insensitive protease from mackerel white muscle.

A pepstatin insensitive protease was purified from mackerel white muscle by a combination of acid treatment, ammonium sulfate fraction, Q Sepharose Fast Flow ion exchange chromato-graphy, Cellulofine GC-200 gel filtration, hydrophobic chromatography on Phenyl-Superose column, chromatofocusing on Mono P column, re-chromatofocusing on the column, and ion ex-change chromatography on Mono Q column. The specific activity of the enzyme increased about 7, 750-fold in 1.6% yield, and the final preparation proved to be homogeneous on polyacryl-amide slab gel electrophoresis.

Morphology and size-distribution of sound and acid-treated enamel crystallites.

Citric acid dissolves crystallites of enamel by initially etching out approximately hexagonal holes in the core of the crystallites, parallel to their long axis. Such acid-treatment influences the crystallite diameter only slightly since the distribution of the diameters of crystallites with a hollow core is not essentially different from those found in sound enamel. In both cases, the average diameter is 37 nm. Crystallites having a central defect and an outer diameter of about 40 nm are split into two parts of approximatley 15 nm in diameter following acid treatment. The central defect is caused exclusively by the acid and not by damage from the electron beam, nor by a combination of acid treatment and electron beam damage.

Kaffircorn malting and brewing studies XVIII—Purification and properties of sorghum malt β‐amylase

AbstractSorghum malt β‐amylase has been purified by a combination of acid treatment, alcohol fractionation, DEAE‐cellulose and calcium phosphate chromatography, and gel filtration. The purified enzyme was shown to be homogeneous in the ultracentrifuge, on electrophoresis and chromatography and no evidence for more than one active form of the enzyme was found. Results are presented for the molecular weight, sedimentation, diffusion, amino‐acid composition, and kinetic properties of the purified enzyme.