The role of chitosan in wool finishing

The application of the biopolymer chitosan as an alternative to the conventional contaminating processes in textiles was studied. As chitosan is produced by biomass, it is biodegradable and bioadsorbable. These properties are increasingly important given the current environmental legislation. The main aim of chitosan treatment of oxidised wool fabrics is to improve felting properties and dyeing behaviour.     

Multifunctional finishing of wool fabrics by chitosan UV-grafting: An approach

The aim of this study was the surface modification of wool fibers to confer a multifunctional finishing to the fabrics, improving the textile value and its applications without damage of comfort properties. The attention was focused on an economical and environmental friendly process to obtain an effective treatment with good durability to washing.     

Chitosan contribution on wool treatments with enzyme

In a previous research work, it was observed that the application of biopolymer chitosan (CHT) on wool fabrics before the enzymatic treatment promotes an increase of the weight loss. In order to deep on the role played by CHT, several experimental conditions have been selected according to a hybrid experimental design and different parameters, such as weight loss and shrink-resist properties, have been controlled. To enhance the CHT sorption on the wool fibre surface, wool was submitted previously to a water-vapour low-temperature plasma treatment. The weight loss results reveal that the enzyme effect increases by increasing the CHT concentration applied to untreated wool. However, CHT concentration does not have any influence when wool has been previously treated with plasma. It is deduced that the surface free energy of wool fibres plays an important role on the enzyme activity. Therefore, the results obtained reveal that the main contribution of CHT on hydrophobic surface of untreated wool fibres is to confer hydrophilicity to wool. Furthermore, CHT tends to coat the wool fibres by film formation reducing apparently the fibre damage promoted by enzyme treatment and also reducing the wool shrinkage.     

Immobilization of hemoglobin on chitosan films as mimetic peroxidase

Hemoglobin (Hb) was immobilized on the chitosan films using glutaraldehyde as a bifunctional agent. Atomic force microscopy (AFM) was used to examine the film surface in order to image the presence of Hb and Fourier transform infrared spectroscopy (FT-IR) was detected to elucidate the structural change of the immobilized Hb. The influences of several immobilization parameters were investigated, the optimum concentration of glutaraldehyde, pH and binding time were determined as 0.7%, 4.5 and 6 h, respectively. The enzymatic assay indicates that the immobilized Hb showed a higher thermal stability than that of free Hb, and the catalytic activity in organic solvents was also enhanced.     

漆酶在磁性壳聚糖微球上的固定及其酶学性质研究

以磁性壳聚糖微球为载体,戊二醛为交联剂,共价结合制备固定化漆酶。探讨了漆酶固定化的影响因素,并对固定化漆酶的性质进行了研究。确定漆酶固定化适宜条件为：50 mg磁性壳聚糖微球,加入10mL 0.8mg/mL 漆酶磷酸盐缓冲液（0.1mol/L,pH 7.0）,在4℃固定2h。固定化酶最适pH为3.0, 最适温度分别为10℃和55℃,均比游离酶降低5℃。在pH 3.0,温度37℃时,固定化酶对ABTS的表观米氏常数为171.1μmol/L。与游离酶相比,该固定化漆酶热稳定性明显提高,并具有良好的操作和存储稳定性。     

Dyeing and antimicrobial characteristics of chitosan treated wool fabrics with henna dye

Chitosan, a naturally available biopolymer which is now increasingly being used as a functional finish on textile substrates to impart antimicrobial characteristics and increase dye uptake of fabrics was applied on wool fabrics. Henna a natural dye with proven bactericidal properties was applied on wool fabrics along with chitosan to impart antimicrobial characteristics. The effect of chitosan application on the dyeing properties of wool fabrics was studied by measuring the K/S values of the treated substrates at various concentrations of chitosan and the dye. The antimicrobial properties of chitosan and natural dyes both when applied independently and collectively on fabrics were assessed. The results proved that the chitosan treated wool fabrics showed increase dye uptake of fabrics. The treated fabrics were found to be antimicrobial and the chitosan treatment enhances the antimicrobial characteristics of the dyes. Fastness properties of the applied finish to washing, rubbing and perspiration have also been discussed.     

The influence of enzymatic treatment on wool fibre properties using PEG-modified proteases

The main contribution of the presented work was to introduce the use of proteases modified with the soluble polymer polyethylene glycol (PEG) in the bio-finishing process of wool fibres, to target enzyme action to the outer parts of wool fibres, i.e. to avoid the diffusion and consequent destroying of the inner parts of the wool fibre structure, in the case of native proteases using.

Different proteolytic enzymes from Bacillus lentus and Bacillus subtilis in native and PEG-modified forms were investigated and their influence on the modification of wool fibres morphology surface, chemical structure, as well as the hydrolysis of wool proteins, the physico-mechanical properties, and the sorption properties of 1:2 metal complex dye during dyeing were studied. SEM images of wool fibres confirmed smoother and cleaner fibre surfaces without fibre damages using PEG-modified proteases. Modified enzyme products have a benefit effect on the wool fibres felting behaviours (14%) in the case when PEG-modified B. lentus is used, without markedly fibre damage expressed by tensile strength and weight loss of the fibre. Meanwhile the dye exhaustion showed slower but comparable level of dye uptake at the end of the dyeing.     

Improvement of chloroperoxidase stability by covalent immobilization on chitosan membranes

Chloroperoxidase (CPO) from Caldariomyces fumago was optimally covalently immobilized on chitosan membranes pretreated with 0.8 M glutaraldehyde at pH 3.5 to give 3.18 mg CPO g⁻¹ support. Using monochlorodimedone (MCD) as assay substrate, the immobilized-CPO retained 40% activity at 50°C after 40 min whereas free CPO retained only 0.02%. The residual activity for immobilized-CPO was 99 and 58% compared with 68 and 43% for free CPO in the presence of 1.5 M urea and 300 μM H₂O₂, respectively, after 20 h.     

A study of the distribution of chitosan onto and within a paper sheet using a fluorescent chitosan derivative

Acidic glutaraldehyde (Gh) crosslinked chitosan (ChGhH) when deprotonated the biopolymer (ChGh) presents high content of free amino groups. These modified biopolymers are comparable to epichlorohydrin (Ep) crosslinked (ChEp). C/N molar ratio of 6.1 for chitosan increases to 7.3, 7.5 and 7.1 for ChGhH, ChGh and ChEp. The effectiveness of the carbon-6 hydroxyl group in interconnecting chitosan units was supported by IR and ¹³CNMR, where Ep promotes increase in crystallinity. Copper uptake gave the order Ch > ChGh > ChGhH > ChEp, as: 1.35 ± 0.06, 1.30 ± 0.05, 1.05 ± 0.07 and 0.96 ± 0.22 mmol g⁻¹, reflecting the availability of nitrogen basic centers in adsorbing. The favorable thermodynamic data of adsorption through calorimetric titration gave exothermic enthalpic values: −28.98 ± 0.05, −6.68 ± 0.04, −6.13 ± 0.07 and −0.65 ± 0.23 kJ mol⁻¹ for Ch, ChGh, ChGhH and ChEp. Free Gibbs energy reflected spontaneity of interactions and, with the exception of chitosan, the entropic values are positive.     

Miscibility study of chitosan/2-hydroxyethyl starch blends and evaluation of their effectiveness as drug sustained release hydrogels

Polymeric matrices of chitosan (CS), 2-hydroxyethyl starch (HES) and their blends prepared by solvent evaporation technique, have been tested as sustained release hydrogels of ropinirole drug. X-Ray diffraction (XRD), infrared spectroscopy (FT-IR) and viscometry measurements showed that the two polymers can form miscible blends. This miscibility is owed to formed hydrogen bonds taking place between the reactive groups of CS and HES and one glass transition is recorded in all blends. Neat polymers were used to prepare solid dispersion formulations with ropinirole drug. It was found that drug was released immediately within 15-30 min from HES while the release was slower from CS matrix. Completely different were the release rates from ropinirole with physical mixtures using neat polymers and their blends. Due to the different solubility and swelling behaviour of CS and HES the release rates showed a sustained profile from the blends containing high amounts of CS.     

Chitosan-LiOH-urea aqueous solution—a novel water-based system for chitosan processing

A solution of partially N-deacetylated chitosan in aqueous lithium hydroxide (LiOH)/urea was prepared successfully through a freeze-thawing process and the dissolution behavior was studied. The results indicated that chitosan can directly dissolve in LiOH/urea aqueous solution. LiOH mainly contributed to the breakage of intramolecular and intermolecular hydrogen bonds in chitosan. Urea, LiOH, and chitosan formed inclusion compound (IC) with urea as the IC host, and the LiOH-chitosan complex as the guest. Aqueous 4.8 wt % LiOH/8.0 wt % urea was verified to be the optimal solvent for chitosan. The results of rheology and viscosity characterizations revealed that chitosan/4.8 wt % LiOH/8.0 wt % urea aqueous solution was pseudoplastic fluid, and was more stable than the solution of chitosan in acetic acid at ambient temperature.     

Cross-linked succinyl chitosan as an adsorbent for the removal of Methylene Blue from aqueous solution

Removal of a basic dye (Methylene Blue) from aqueous solution was investigated using a cross-linked succinyl-chitosan (SCCS) as sorbent. The chemical structures of chitosan and its derivatives were testified by FT-IR. X-ray diffraction, DTG analysis and swelling measurements were conducted to clarify the characteristics of the chemically modified chitosan. The effect of process parameters, such as pH of the initial solution, and concentrations of dyes on the extent of Methylene Blue (MB) adsorption was investigated. The Langmuir isotherm model was used to fit the equilibrium experimental data, giving a maximum sorption capacity of 289.02 mg/g at 298 K. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were determined to be −25.32 kJ mol⁻¹, −6.76 kJ mol⁻¹ and −62.36 J mol⁻¹ K⁻¹, respectively, which leads to a conclusion that the adsorption process is spontaneous and exothermic.     

Encapsulation of Haematococcus pluvialis using chitosan for astaxanthin stability enhancement

Astaxanthin is receiving commercial interest due to its use as a preferred pigment in aquaculture feeds. Its antioxidant activity is approximately 100 times higher than that of β-tocopherol, and can be used as a potential agent against cancer. Astaxanthin can easily be degraded by thermal or oxidative processes during the manufacture and storage. In this study, astaxanthin and its biological activity were protected against oxidative environmental conditions by encapsulating the homogenized cells in chitosan. Haematococcus pluvialis were formed into beads, which were then coated with 5 layers of chitosan film, resulting in chitosan-algae capsules that have a mean diameter of 0.43 cm and the total film thickness of approximately 100 μm. No significant loss in the amount of astaxanthin content in H. pluvialis was found due to the process of encapsulation. However, approximately 3% loss of antioxidant activity of the H. pluvialis was observed after encapsulation. The results of stability under different storage conditions showed that although encapsulation caused 3% loss of antioxidant activity, the longer term stability of the dried algae biomass, beads, and capsules indicated that encapsulation of H. pluvailis in chitosan film was capable of protecting the algae cells from oxidative stresses.     

Immobilization of horseradish peroxidase on activated wool

This work is aimed to immobilize partially purified horseradish peroxidase (HRP) on wool activated by multifunctional reactive center, namely cyanuric chloride. The effect of cyanuric chloride concentration, pH and enzyme concentration on immobilization of HRP was studied. FT-IR and SEM analyses were detected for wool, activated wool and immobilized wool-HRP. The wool-HRP, prepared at 2% (w/v) cyanuric chloride and pH 5.0, retained 50% of initial activity after seven reuses. The wool-HRP showed broad optimum pH at 7.0 and 8.0, which was higher than that of the soluble HRP (pH 6.0). The soluble HRP had an optimum temperature of 30 °C, which was shifted to 40 °C for immobilized enzyme. The soluble and wool-HRP were stable up to 30 and 40 °C after incubation for 1 h, respectively. The apparent kinetic constant values (K_ms) of wool-HRP were 10 mM for guiacol and 2.5 mM for H₂O₂, which were higher than that of soluble HRP. The wool-HRP was remarkably more stable against proteolysis mediated by trypsin. The wool-HRP exhibited more resistance to heavy metal induced inhibition. The wool-HRP was more stable to the denaturation induced by urea, Triton X-100, isopropanol, butanol and dioxan. The wool-HRP was found to be the most stable under storage. In conclusion, the wool-HRP could be more suitable for several industrial and environmental purposes.     

Effect of ultrasonic treatment on the biochemphysical properties of chitosan

Four chitosans with different molecular weights and degrees of deacetylation degree and 28 chitosans derived from these initial chitosans by ultrasonic degradation have been characterized by gel permeation chromatography (GPC), FT-IR spectroscopy, X-ray diffraction and titrimetric analyses. Antimicrobial activities were investigated against E. coli and S. aureus using an inhibitory rate technique. The results showed that ultrasonic treatment decreased the molecular weight of chitosan, and that chitosan with higher molecular weight and higher DD was more easily degraded. The polydispersity decreased with ultrasonic treatment time, which was in linear relationship with the decrease of molecular weight. Ultrasonic degradation changed the DD of initial chitosan with a lower DD (<90%), but not the DD of the initials chitosan with a higher DD (>90%). The increased crystallinity of ultrasonically treated chitosan indicated that ultrasonic treatment changed the physical structure of chitosan, mainly due to the decrease of molecular weight. Ultrasonic treatment enhanced the antimicrobial activity of chitosan, mainly due to the decrease of molecular weight.     

Immobilization and characterization of horseradish peroxidase into chitosan and chitosan/PEG nanoparticles: A comparative study

Chitosan (CS) is considered a suitable biomaterial for enzyme immobilization. CS combination with polyethylene glycol (PEG) can improve the biocompatibility and the properties of the immobilized system. Thus, the present work investigated the effect of the PEG in the horseradish peroxidase (HRP) immobilization into chitosan nanoparticles from the morphological, physicochemical, and biochemical perspectives. CS and CS/PEG nanoparticles were obtained by ionotropic gelation and provided immobilization efficiencies (IE) of 65.8 % and 51.7 % and activity recovery (AR) of 76.4 % and 60.4 %, respectively. The particles were characterized by DLS, ZP, SEM, FTIR, TGA and DSC analysis. Chitosan nanoparticles showed size around 135 nm and increased to 229 nm after PEG addition and HRP immobilization. All particles showed positive surface charges (20−28 mV). Characterizations suggest nanoparticles formation and effective immobilization process. Similar values for optimum temperature and pH for immobilized HRP into both nanoparticles were found (45 °C, 7.0). V_max value decreased by 5.07 to 3.82 and 4.11 mM/min and K_M increased by 17.78 to 18.28 and 19.92 mM for free and immobilized HRP into chitosan and chitosan/PEG nanoparticles, respectively. Another biochemical parameters (K_cat, K_e, and K_α) evaluated showed a slight reduction for the immobilized enzyme in both nanoparticles compared to the free enzyme.     

Development and industrialisation of enzymatic shrink-resist process based on modified proteases for wool machine washability

There is currently considerable interest in the use of enzymes to achieve a variety of finishing effects on wool, but it is apparent that the extent of fibre degradation by enzymes is of major concern during their commercial application. Proteolytic enzymes are known to penetrate and degrade the internal wool structure during processing, causing fibre damage, rather than limiting the degradation to the cuticle cells. The ability to be able to control the exact location of proteolytic attack on wool protein structures will lead to the successful development of enzymatic treatments for achieving a variety of finishing effects for wool-containing products. This present work describes the modification of proteases so that enzymatic modification of wool fibres is restricted to the cuticle scales of the fibres.

Bulk trials have demonstrated that novel modifications of the enzyme enable the reaction of the enzyme with wool to be controlled, so that less degradation of the wool occurs than in similar treatments with the native protease. An anti-felting effect has been achieved without any significant weight loss being caused by the modified protease during the treatment. This novel enzymatic process leads to environmentally friendly production of machine washable wool.     

The removal of lipid from the surface of wool to promote the subsequent enzymatic process with modified protease for wool shrink resistance

Abstract

When treated with modified protease, wool shows shrink resistance without significant damage to the fiber. It was considered that if wool fiber was pre-treated to make it more hydrophilic, the subsequent treatment with modified protease would be more efficient. After wool was pre-treated with cetyltrimethylammonium bromide (CTAB) under alkaline conditions, the fiber became very hydrophilic due to the removal of surface lipid. After CTAB treatment, it was found that residual CTAB on the fiber significantly decreased enzyme activity. Therefore prior to enzyme treatment, CTAB was washed off the fiber with anionic surfactant under acidic conditions. It was found that the activity of modified protease towards wool improved if wool had been pre-treated with CTAB then washed with anionic surfactant. It was concluded that pre-treatment of wool with CTAB under alkaline conditions followed by washing with anionic surfactant improves the wettability of wool and therefore promotes more efficient treatment with modified protease, achieving improved levels of shrink resistance with no effect on strength of the fiber or coloration properties.     

Immobilization of α-amylase from mung beans (Vigna radiata) on Amberlite MB 150 and chitosan beads: A comparative study

α-Amylase from mung beans (Vigna radiata) was immobilized on two different matrices, Amberlite MB 150 and chitosan beads. Maximum immobilization obtained was 72% and 69% in case of Amberlite and chitosan beads, respectively. The pH optima of soluble α-amylase were 5.6, whereas that for immobilized amylase on chitosan and Amberlite was 7.0. Soluble amylase and Amberlite immobilized amylase showed maximum activity at 65 °C, whereas chitosan immobilized amylase showed maximum activity at 75 °C. α-Amylase immobilized on Amberlite showed apparent K_m of 2.77 mg/ml, whereas α-amylase immobilized on chitosan showed an apparent K_m of 5 mg/ml. The Amberlite-amylase and chitosan-amylase showed a residual activity of 43% and 27%, respectively, after 10 uses. The loss of activity for free amylase after 100 days of storage at 4 °C was 70%, whereas that for Amberlite- and chitosan-amylases, under the same experimental conditions, the losses were 45% and 55%, respectively. The easy availability of mung bean α-amylase, the ease of its immobilization on low-cost matrices and good stability upon immobilization in the present study makes it a suitable product for further use in industrial applications.     

An evaluation of the action of thioesterases on the surface of wool

The thioesterase activity of palmitoyl protein thioesterase (PPT1) and six commercial lipases was measured against the synthetic substrates, S-palmitoyl-N-acetylcysteamine (Ac-Cym-Pal) and S-(18-methyleicosanoyl)-N-acetylcysteamine (Ac-Cym-18-MEA). PPT1 showed good activity against Ac-Cym-Pal but relatively low activity against the longer chain substrate, Ac-Cym-18-MEA. The highest activity was given by Lipolase 100L type EX (Novozyme) and Lipoprotein Lipase (Sigma) with greater than 90% hydrolysis of Ac-Cym-18-MEA within 10 min at pH 7.4. Other lipases to show high levels of thioesterase activity include Lipex 100L (Novozyme), Lipomod 34P (Biocatalysts) and Lipozyme CALB L (Novozyme). Chemical analysis of wool fibre and fabric treated with the above enzymes under optimal conditions showed that there was no hydrolysis of 18-MEA or other covalently bound fatty acids from the fibre surface. No change in the wettability of the fabric surface was observed following enzyme treatments. Scanning electron micrographs of the fabric treated with the most active enzyme, Lipolase 100L type EX, revealed that the surface of the fibres appeared to have a coating that was not removed by extensive extraction. Reasons for the inability of PPT1 and the other esterases to hydrolyse 18-MEA from the wool fibre surface are discussed.