Effect of post- and pre-crosslinking of cotton fabrics on the efficiency of biofinishing with cellulase enzyme

Four different types of cotton-based fabrics, namely, loom-state cotton, cotton/polyester (50/50), cotton/polyester (35/65) and grey mercerized fabrics were bioscoured and bleached. The four substrates are given enzymatic treatment using cellulase enzyme to affect bio-polishing followed by crosslinking using N,N-dimethylol 4,5-dihydroxyethylene urea (DMDHEU) to affect easy care finishing. In another series of experiments the said bioscoured–bleached substrates were similarly crosslinked followed by bio-polishing. Technical properties of the treated fabric that were monitored include: nitrogen content, loss in fabric weight, tensile strength, elongation at break, tear strength, whiteness index, surface roughness and wrinkle recovery angle. Scanning electron micrograph was also examined. Conclusions arrived at from these studies indicated that: post-crosslinking and pre-crosslinking revealed marginal differences in N%, wrinkle recovery angle and whiteness index, a point which validates the argument that cellulase enzyme could not break down the DMDHEU crosslinks within the molecular structure of cotton-containing fabrics. Meanwhile the surface roughness obtained with pre-crosslinking is a bit higher than those of post-crosslinking. Moreover, post-crosslinking caused higher losses in strength properties than pre-crosslinking. Scanning electron micrograph shows that cotton sample pre-crosslinked is almost smooth than those post-crosslinked.     

An eco-friendly – novel approach for attaining wrinkle – free/soft-hand cotton fabric

A novel approach for upgrading both the wrinkle free and softness properties of cotton fabrics without adversely affecting their strength properties using an eco-friendly finishing regimes was investigated. Factors affecting the performance properties of the finished substrate such as pre-treatment, i.e., carboxymethylation (CMC) or ionic-crosslinking, post-treatment with amino functional silicone softener and its concentration, degree of carboxymethylation as well as thermofixation conditions were studied. The obtained results revealed that post-treatment with the amino based silicone micro emulsion (SiE) up to 30 g/L at pH 4 to a wet pickup of 100% followed by drying at 100 °C for 5 min and curing at 170 °C for 3 min results in a remarkable improvement in fabric resiliency (expressed as dry and wet wrinkle recovery angles), as well as in softness degree, without seriously affecting its retained strength. Improvement extent of the aforementioned properties is governed by the nature of the pre-treatment steps. Fixation of the amino-functional silicone softener onto/or within the modified cellulose structure is accompanied by a formation of semi-inter and/or intra-penetrated network (semi-IPN) thereby enhancing both the extent of crosslinking and networking as well as providing very high softness. FTIR analysis proved the formation of Si–O–Si–cellulose complex. Scanning electron micrograph shows that cotton, CMC and ionic crosslinked cotton fabrics treated with SiE shows higher surface smoothness and considerable reduction in protruding loose fibers, ditches and grooves compared with the untreated one.     

Hypophosphite oxidase fromBacillus caldolyticus

Bacillus caldolyticus can utilize phosphorus either as phosphate, phosphite, or hypophosphite. When cultures are supplied with PO₂ as the sole source of phosphorus, the hypophosphite is oxidized to phosphate, which accumulates in the medium prior to the beginning of the log phase, and is then metabolised during growth. Resting cell suspensions also have the ability to oxidise PO₂ to PO₄. The reaction is specific for hypophosphite: PO₃ is not oxidised to PO₄, regardless of whether the cells are grown in PO₃- or PO₂-medium. The hypophosphite oxidase works optimally between pH 7.0 to 7.5, with a temperature optimum at 75°C; theK _m for NaH₂PO₂ is 320 μM. Sonication of cells, followed by high-speed centrifugation and ammonium sulfate fractionation of the cell-free extract showed that the PO₂ oxidation, which is accompanied by the formation of NADH, requires at least three components: An ammonium sulfate fraction of the cell-free extract, the residue fraction containing the respiratory chain, and NAD as cofactor. Most probably a second cofactor, so far not characterized, is required to accomplish full activity.     

Finishing of cotton fabrics with poly (N-vinyl-2-pyrrolidone) to improve their performance and antibacterial properties

Cotton fabric was thermally crosslinked with poly (N-vinyl-2-pyrrolidone) (PVP) at different conditions including temperature, time, PVP concentrations and molecular weights. Results indicated that treating the cotton fabrics with 4% aqueous solution of PVP of molecular weight 10,000 Dalton followed by drying at 85 °C for 5 min then curing at 160 °C for 3 min results in crosslinking as will as an improvement in some performance properties of that fabrics such as resiliency, tensile strength, and acid dyeability. Post-treating PVP crosslinked fabric with 5% iodine in ethanol solution for 5 h at 50 °C imparts antibacterial activity against Staphylococcus aureus and Escherichia coli. Moreover, incorporation of PVP in the easy-care finishing of cotton fabrics, as polymer additive, with N,N-dimethylol 4,5-dihydroxyethylene urea as a crosslinker enhances some of the performance properties of finished fabrics such as the nitrogen content, tensile strength and acid dyeability along with decreasing resiliency as well as whiteness index, whereas the ester crosslinking with citric acid, in presence of PVP, enhances resilience, tensile strength and whiteness indices accompanied with a reduction in the %N of the treated fabrics. Infra red spectrum of PVP crosslinked fabric as well as EDX analysis of loaded iodine on PVP crosslinked cotton fabric were investigated.     

Cutinase promotes dry esterification of cotton cellulose

Cutinase from Thermobifida fusca was used to esterify the hydroxyl groups of cellulose with the fatty acids from triolein. Cutinase and triolein were pre‐adsorbed on cotton and the reaction proceeded in a dry state during 48 h at 35°C. The cutinase‐catalyzed esterification of the surface of cotton fabric resulted in the linkage of the oleate groups to the glycoside units of cotton cellulose. The superficial modification was confirmed by performing ATR‐FTIR on treated cotton samples and by MALDI‐TOF analysis of the liquors from the treatment of the esterified cotton with a crude cellulase mixture. Modified cotton fabric also showed a significant increase of hydrophobicity. This work proposes a novel bio‐based approach to obtain hydrophobic cotton. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:60–65, 2016     

Immobilization of cellulases on the reversibly soluble polymer Eudragit S‐100 for cotton treatment

Cellulases can penetrate into the fiber, causing tensile strength loss of the cellulosic fibers or fabrics. To minimize the tensile strength loss, we have immobilized cellulases on Eudragit S‐100. The characteristics of covalent Eudragit cellulase were evaluated using gel filtration analysis and UV spectra. Gel filtration analysis revealed that the cellulases were covalently bound to the polymer. Covalent Eudragit cellulase was loaded with the enzyme of about 40% and had a relative activity about 80% at a Eudragit S‐100 concentration of 15 g/L. When cellulase is bound to the polymer, the solubility profile becomes similar to the one of Eudragit. In addition, the effects of the enzyme on the cotton yarns and fabric using cellulases have been investigated. Native and immobilized cellulases caused improvements in whiteness and wrinkle recovery angle of the fabric in comparison to the control samples. The bending stiffness results show that native and immobilized cellulase treated cotton fabric has an improved softness than the control samples. It was found that using the immobilized cellulase reduced the weight and tensile strength, because the hydrolytic attack is only limited to the surfaces of cotton fibers.     

Effect of microwave irradiation on the physical properties and morphological structures of cotton cellulose

Microwave heating has been proved to be more rapid, uniform and efficient, and easily penetrate to particle inside. To investigate the effect of microwave irradiation on the physical property and morphological structure of cotton cellulose, cellulose fabric was treated with microwave irradiation at different conditions. The physical properties of the treated cellulose fabric were investigated. The morphological structures and thermal stabilities of the untreated and treated cellulose were investigated with differential scanning calorimetry (DSC) and X-ray diffraction. The results show that the physical properties of the treated cellulose fabrics were improved and the recoverability had not significant change. The thermal stability of the treated cellulose was changed. The crystallinity and preferred orientation of the treated cotton cellulose increased.     

Rapid microwave-assisted synthesis and characterization of cellulose-hydroxyapatite nanocomposites in N,N-dimethylacetamide solvent

Preparation of nanocomposites was carried out using microcrystalline cellulose, CaCl₂, and NaH₂PO₄ in N,N-dimethylacetamide (DMAc) solvent by a microwave-assisted method at 150 °C. XRD results showed that the nanocomposites consisted of cellulose and hydroxyapatite (HA). The cellulose existed as a matrix in the nanocomposites. SEM and TEM analysis showed that HA nanorods were homogeneously dispersed in the cellulose matrix. The effects of the microwave heating time on the products were investigated. This method has advantages of being simple, rapid, low-cost, and environmentally friendly.     

Flame retardant finishing of cotton fabric based on synergistic compounds containing boron and nitrogen

Boric acid and compound containing nitrogen, 2,4,6-tri[(2-hydroxy-3-trimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-HTAC) were used to finish cotton fabric. The flame retardant properties of the finished cotton fabrics and the synergetic effects of boron and nitrogen elements were investigated and evaluated by limited oxygen index (LOI) method. The mechanism of cross-linking reaction among cotton fiber, Tri-HTAC, and boric acid was discussed by FTIR and element analysis. The thermal stability and surface morphology of the finished cotton fabrics were investigated by thermogravimetric analysis (TGA) and scanning electron microscope (SEM), respectively. The finishing system of the mixture containing boron and nitrogen showed excellent synergistic flame retardancy for cotton fabric. The cotton fabric finished with mixture system had excellent flame retardancy. The LOI value of the treated cotton fabric increased over 27.5. Tri-HTAC could form covalent bonds with cellulose fiber and boric acid. The flame retardant cotton fabric showed a slight decrease in tensile strength and whiteness. The surface morphology of flame retardant cotton fiber was smooth.     

Production of poly-β-hydroxybutyrate by thermophilic cyanobacterium, Synechococcus sp. MA19, under phosphate-limited conditions

Synechococcus sp. MA19, grown autotrophically under phosphate-limited conditions at 50 °C, produced poly--hydroxybutyrate (PHB) when intracellular phosphate content was 0.043–0.076mmol per g of cellular components. In the culture for 260h using Ca₃(PO₄)₂ as a phosphate source, strain MA19 accumulated PHB at 55% (w/w) of the dry cells and the amount of PHB produced was 2.4gl^–1 which was almost twice that without Ca₃(PO₄)₂ addition.     

Cellulose esters from waste cotton fabric via conventional and microwave heating

The esterification of cellulose from waste cotton fabric in a N,N-dimethylacetamide/lithium chloride solvent system was carried out using different types of fatty acid chloride including butyryl chloride, capryloyl chloride, and lauroyl chloride as esterifying agents, and N,N-dimethyl 1-4-aminopyridine as a catalyst under conventional and microwave activation. Microwave esterification was performed under 2.45 GHz with power varying from 90 to 450 W. The optimum conditions for esterification of cotton cellulose with various esterifying agents were investigated in terms of reaction time and temperature to attain appropriate %weight increase and degree of substitution of esterified-cellulose. The degree of substitution, functional group and chemical structure, and thermal stability of cellulose ester powder were characterized by ¹H NMR, FTIR, and TGA/SDTA analysis. Morphologies, crystallinity, and solubility of modified cellulose by two different heating methods were compared.     

Interaction between Casein and Carboxymethyl Cellulose in the Acidic Condition

The stabilizing action of carboxymethyl cellulose (CMC-1 and CMC-2) on caseins was studied in the acidic pH region. CMC-1 stabilized 1% whole, α-, α_S- and β-casein at pH 4.6 and 5.0, and at 5°C. But CMC-2 could not completely stabilize these caseins at pH 5.0. Interaction between κ-casein and CMC-1 commenced when pH was adjusted to 6.3, but CMC-2 interacted with κ-casein below pH 5.6. An α_S- and κ-casein mixture (4 : 1) with CMC-2 was destabilized by the addition of 0.02 m NaCl or NaH₂PO₄ at pH 5.0. The α_S/κ ratio of the precipitated casein was about 10. But the same system with CMC-1 was not destabilized by the salts.     

New development for combined bioscouring and bleaching of cotton-based fabrics

A thorough investigation into conditions appropriate for effecting combined eco-friendly bioscouring and/or bleaching of cotton-based fabrics was undertaken. Fabrics used include cotton, grey mercerized cotton, cotton/polyester blend 50/50 and cotton/polyester blend 35/65. The four cotton-based fabric were subjected to bioscouring by single use of alkaline pectinase enzymes or by using binary mixtures of alkaline pectinase and cellulase enzymes under a variety of conditions. Results of bioscouring show that, the bioscoured substrates exhibit fabrics performances which are comparable with these of the conventional alkali scouring. It has been also found that, incorporation of ethylenediaminetetraacetic acid (EDTA) in the bioscouring with mixture from alkaline pectinase and cellulase improves the performance of the bioscoured fabrics. Addition of β-cyclodextrin to the bioscouring solution using alkaline pectinase in admixtures with cellulase acts in favor of technical properties and performance of the bioscoured fabrics. Concurrent bioscouring and bleaching by in situ formed peracetic acid using tetraacetylethylenediamine (TAED) and H₂O₂ was also investigated. The results reveal unequivocally that the environmentally sound technology brought about by current development is by far the best. The new development involves a single-stage process for full purification/preparation of cotton textiles. The new development at its optimal comprises treatment of the fabric with an aqueous formulation consisting of alkaline pectinase enzyme (2 g/L), TAED (15 g/L), H₂O₂ (5 g/L), nonionic wetting agent (0.5 g/L) and sodium silicate (2 g/L). The treatment is carried out at 60 °C for 60 min. Beside the advantages of the new development with respect to major technical fabric properties, it is eco-friendly and reproducible. This advocates the new development for mill trials.     

Dansyl chloride-stained nucleolar organizers and core-like structures in Chinese hamster metaphase chromosomes

When chromosomes containing both BrdU-substituted and unsubstituted regions were treated with hot NaH₂PO₄ at high or low pH and then stained with dansyl chloride, brightly fluorescent nucleolar organizer regions (NORs) and core-like structures were apparent in the chromosomes. These structures closely parallel the appearance of the same structures in silver-stained chromosomes. Since dansyl chloride is a protein-specific fluorochrome, the distribution of fluorescence suggests that the NORs and central zone of each chromatid contain higher concentrations of protein relative to other chromosome regions. The fluorescent core structures are interpreted to be artefacts of the NaH₂PO₄ pretreatment induced by changes in the concentration of chromatin (including protein) between the chromatin-dense center and more dispersed peripheral region of each chromatid.     

The Effect of Lowered Concentrations of Carbon,Nitrogen and Phosphorus Sources on the Growth Dynamics of the R,S, and M Dissociants of Pseudomonas aeruginosa

The effect of lowered concentrations of carbon, nitrogen, and phosphorus sources in the medium on the specific growth rate of the R, S, and M dissociants of the hydrocarbon-oxidizing strain Pseudomonas aeruginosaK-2, culture pH, and the population composition was studied. Within the first 16 hours of cultivation in all of the four media tested, the R, S, and M dissociants have virtually identical . The maximal values of were reached by the 20th h of growth in the basal medium (R and S dissociants) and in the carbon-deficient medium containing 0.4% glucose (M dissociant). The R and M dissociants showed the most rapid decrease in in the nitrogen-deficient medium containing 0.55% NaNO₃. By the end of cultivation in the basal medium, the pH of the R, S, and M cultures decreased to 6.3, 5.3, and 3.3, respectively. In the case of the carbon-deficient medium, the drop in the culture pH was lower. After a 2.5-day incubation of the S dissociant in the phosphorus- deficient medium containing 0.028% NaH₂PO₄· 2H₂O and of the M dissociant in the basal medium supplemented with chalk powder, these dissociants were completely displaced from the media.     

氮磷添加与不同栽植密度交互对樟树幼苗土壤化学性质的短期影响

研究氮磷添加对不同密度樟树(Cinnamomum camphora)幼苗土壤化学性质的影响,以期为全球化背景下樟树人工林生态系统的土壤养分管理提供依据。以1年生樟树幼苗为试验材料,选择氯化铵(NH4Cl)作为氮肥模拟大气氮沉降,以二水合磷酸二氢钠(NaH_2PO_4·2H_2O)模拟磷添加。氮磷处理设置CK、施N、施P和施N+P 4个水平,其中N、P和N+P施肥量分别为40 g m~(-2)a~(-1)(NH_4Cl)、20 g m-2a-1(NaH_2PO_4·2H_2O)和40g m~(-2)a~(-1)(NH_4Cl)+20 g m~(-2)a~(-1)(NaH_2PO_4·2H_2O)。种植密度设置4个水平:10、20、40和80株/m~2,试验时间为2017年6月至9月。研究结果表明,在各密度幼苗土壤中,N和N+P处理引起pH值的显著下降,N、P和N+P处理的土壤有机质和碱解N含量的变化规律不明显,P处理的幼苗土壤全P含量上升,P和N+P处理的土壤有效P含量增加,N+P处理的土壤全K含量以及N、P和N+P处理的土壤速效K含量均下降。在10、20和40株/m~2幼苗的土壤中,P处理的土壤全N含量高于N和N+P处理的,而80株/m~2幼苗的土壤全N含量低于其他密度幼苗。随着种植密度的增加,各施肥处理的土壤pH、全P、有效P、全K和速效K含量均呈现上升趋势,而施N和施P处理的土壤有机质呈现下降趋势,各施肥处理的土壤碱解N含量变化规律不明显。施肥和密度处理对樟树幼苗土壤有机质、碱解氮和速效钾含量有显著的交互作用。     

Preparation of polyethylene glycol/polyacrylamide adduct and utilization in cotton finishing

Highly concentrated aqueous solutions of acrylamide (Am) were polymerized in presence of polyethylene glycol (PEG) using ammonium persulfate as initiator under different conditions including ammonium persulfate concentration (0.02–0.06 g/gAm) temperature (60–95 °C), Am/PEG400 ratio (1/1–1/5 g/g), PEG molecular weight (400–6000). At optimum reaction conditions a PEG 400/PAm adduct was prepared with a % total conversion of 99.7 in 2 min using ammonium persulfate (0.05 g/gAm), Am/PEG (1/2 g/g) at 70 °C. The structure of the adduct was confirmed by FT-IR spectra. The adduct was utilized as a finishing additive for cotton fabric in presence and absence of dimethyloldihydroxy ethylene urea (DMDHEU) by the bad – dry – cure method. In absence of DMDHEU, the adduct improves the fabric tensile strength, stiffness and oily stain release rating without affect the wettability along with decreasing the fabric resiliency compared to the blank sample. Inclusion DMDHEU the finishing bath (50 g/l) results in improving the fabric resiliency and stiffness as well as decreasing the strength, wettability and oily stain release compared to those of fabric treated with adduct in absence of DMDHEU. However, at an adduct concentration of 40 g/l and in presence of 50 g/l DMDHEU the fabric properties are in general, superior to those of blank fabric.     

Antimicrobial and chemical detoxifying functions of cotton fabrics containing different benzophenone derivatives

Several benzophenone chromophoric groups were incorporated onto cotton fabrics by using 4-hydroxybenzophenone, 4,4′-dihydroxybenzophenone, 4-chloro-4′-hydroxybenzophenone, and 4-benzoylbenzoic acid as reagents. The fabric treatment was conducted by a pad-dry-cure method, and the benzophenone chromophoric group incorporated cotton fabrics were characterized and confirmed by FTIR. Tensile strengths of benzophenone chromophoric groups modified cotton fabrics were also measured. 4-Hydroxybenzophenone treated cotton fabric showed the most powerful antibacterial activity among all samples, and 4-benzoylbenzoic acid treated cotton fabric demonstrated pesticide degradation ability, under UV irradiation.     

Amino silicones finished fabrics for lipase immobilization: Fabrics finishing and catalytic performance of immobilized lipase

Finishing of silk fabric was achieved by using amino-functional polydimethylsiloxane (PDMS) and lipase from Candida sp. 99-125 was immobilized on the treated silk fabrics. Hydrophobic fabrics were obtained by dipping the native fabric in 0.125–0.25% (w/v) PDMS solution and dried at 70 °C. The direct adsorption on PDMS-treated fabric was verified to be a better strategy for lipase immobilization than that by covalent binding. Compared to unfinished fabrics, the hydrolytic activity of immobilized enzyme on the finished fabric was improved by 1.6 times. Moreover, the activity of immobilized enzymes on hydrophobic fabrics was significantly improved in different concentrations of strong polar solvents such as methanol and ethanol, and in common organic solvents with different octanol–water partition coefficients (Log P). Enzymatic activity and stability in 15% water content system (added water accounted for the total reaction mixtures, v/v) showed more than 30% improvement in each batch. The amino–silicone finished fabric surface was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. The hydrophobic fabric immobilized enzyme could be recycled for more than 80 times with no significant decrease in esterification activity. PDMS-treated woven silk fabrics could be a potential support for lipase immobilization in catalytic esterification processes.     

Microwave curing for producing cotton fabrics with easy care and antibacterial properties

A new microwave curing system was used to affect crosslinking of cotton fabric with nonformaldehyde finishes, namely, glyoxal, glutaraldehyde and 1,2,3,4 butanetetracarboxylic acid (BTCA). Water soluble chitosan was incorporated in the finishing bath in order to impart antibacterial activity to the fabric in addition to the ease of care characteristics. Glyoxal proved to be the best finish and, hence, it was studied along with the chitosan under a variety of conditions including chitosan concentrations, power and time of microwave curing. Besides the crease recovery and strength properties of the finished fabrics, the latter were also monitored for N%, antibacterial activity and characterized using scanning electron microscope (SEM) and FTIR spectra when compared. With conventional curing system, the microwave curing system was found advantageous in production of cotton fabrics with easy care antibacterial properties without high losses in strength properties.