David Bishop

Effects of Agitation and Endoglucanase Pretreatment on the Hydrolysis of Cotton Fabrics by a Total Cellulase

We have attempted to clarify the effects of low and high levels of mechanical agitation on the cellulolytic activity of a pure endoglucanase ( EG ) and a total cellulase mixture (TC) on scoured and bleached cotton fabric, along with the effect of EG pretreatment on subsequent treatments with TC. Methods used to follow the progress of fabric treatments include weight loss, breaking load loss, bending hysteresis, and the pro duction of soluble reducing sugars and reducing end groups in the fibers. The results show that agitation rate affects the mechanism of cellulolytic attack, and that this has implications for delivering desired finishing effects.

Effects of agitation level on the adsorption, desorption, and activities on cotton fabrics of full length and core domains of EGV (Humicola insolens) and CenA (Cellulomonas fimi).

The activities (at pH 7 and 50 degrees C) of purified EGV (Humicola insolens) and CenA (Cellulomonas fimi) were determined on cotton fabrics at high and low levels of mechanical agitation. Similar activity measurements were also made by using the core domains of these cellulases. Activity experiments suggested that the presence of cellulose binding domains (CBDs) is not essential for cellulase performance in the textile processes, where high levels of mechanical agitation are applied. The binding reversibilities of these cellulases and their cores were studied by dilution of the treatment liquor after equilibrium adsorption. EGV showed low percentage of adsorption under both levels of agitation. It was observed that the adsorption/desorption processes of cellulases are enhanced by higher mechanical agitation levels and that the binding of cellulase with CBD of family I (EGV) is more reversible than that of CBD of the cellulase of family II (CenA).

HYDROLYSIS OF COTTON CELLULOSE BY ENGINEERED CELLULASES FROM TRICHODERMA REESEI

We have characterized the activities of TC, EG-rich, and CBH-rich cellulases from T. reesei and have shown that their activities towards cotton fabrics are influenced by ionic strength and adsorbed ionic species as well as by temperature and pH. Adsorption and kinetic experiments confirm that increasing mechanical agitation favors EG attack by greatly increasing the availability of sites for EG adsorption. It is not clear whether this is a consequence of fiber fibrillation damage or of improved access to fiber surfaces deep within the fabric structure. The enhanced rate of cellulolytic hydrolysis of mer cerized cotton and the inhibitory effects on reactive and direct dyed fabrics are ex plained mainly in terms of increased or reduced availability of adsorption sites for CBHS and EGS. The implications for textile finishing are far-reaching. It is clear that a fabrics processing history (especially mercerizing and dyeing), construction, and level of ap plied mechanical agitation can be as important as the choice of enzyme composition and concentration in determining the consistency and quality of the end result.

Cellulase finishing of woven, cotton fabrics in jet and winch machines

Some authors have reported that as the applied agitation rate increases, the apparent activity of the endoglucanases from Trichoderma reesei towards cotton cellulose increases more markedly than does the apparent activity of the cellobiohydrolases. This suggests that the quality of cellulase finishing effects on cellulosic textiles may be machine-type dependent. The present work using total crude, endoglucanase-rich and cellobiohydrolase-rich cellulases from T. reesei confirmed that the final properties of woven, cotton fabrics treated under realistic processing conditions in a jet machine, were measurably and perceivably different from those of the same fabrics, treated using the same processing conditions of temperature, time, pH, enzyme concentration and fabric to liquor ratio, but in a winch machine. The results are interpreted in terms of the effects of agitation rate on the adsorption-desorption behaviour of the T. reesei endoglucanases and cellobiohydrolases.

Using cellulases to improve the dimensional stability of cellulosic fabrics

Cellulosic fabrics of various constructions and fiber compositions are treated with cellulases under pad-batch conditions. All treated fabrics exhibit commercially significant improvements in dimensional stability after subsequent washing and drying cycles. The enzyme treatments are optimized in terms of cellulase concentration, wet pick-up, cellu lase composition, and batching time. Development samples of specific EG-rich cellulases used at 1.0 to 5.0 mg per gram of fabric give good results in terms of low shrinkage. with fabric weight and strength losses well within commercially acceptable limits. The im provements in dimensional stability compare favorably with those achieved by durable press finishing, but without deterioration of fabric handle. This work formed part of a wider European Commission-funded project (Brile-Euram III project 2157), and a patent application relating to the preferred cellulase/pad-batch process has been filed (WO0153592, published in August 2001).

An ethoxylated alkyl phosphate (anionic surfactant) for the promotion of activities of proteases and its potential use in the enzymatic processing of wool

Pretreatments of wool fabrics with cationic, anionic or non-ionic surfactants were investigated to reduce surface tension and improve the wettability of the fibres in order to promote protease activity on the fibres in subsequent processes. Results showed that an ethoxylated alkyl phosphate (specific anionic surfactant) as well as the widely used non-ionic surfactant was compatible with proteases in the enzymatic treatment of wool. There is therefore a potential for using specific anionic surfactants to achieve efficient enzymatic scouring processes.

Possibilities for recycling cellulases after use in cotton processing: part II: Separation of cellulases from reaction products and released dyestuffs by ultrafiltration.

The adsorption and activity of a total cellulase (Trichoderma reesei) was measured and compared on undyed and dyed cotton fabrics. Recovery of enzymes from the reaction mixture and by desorption from the cotton substrate was evaluated. About 80% of the initial protein could be recovered. The removal of released products (soluble reducing sugars and dyes) from the treatment liquor and subsequent concentration of cellulase proteins was performed using an ultrafiltration membrane. Strong protein-dye interactions made it impossible to separate efficiently the dyes from the enzymecontaining treatment liquors. The use of surfactants did not enhance cellulase desorption from cotton fabric. Although anionic surfactants have a deactivating effect on cellulases, this effect seems to be reversible, since after ultrafiltration the cellulase activity was similar to that of enzymes desorbed with buffer only. Humicola insolens cellulases were shown to be much more sensitive to anionic surfactant than T. reesei cellulases. The use of cellulases that bind reversibly to cellulose is suggested for achieving more efficient cellulase recycling and for reducing backstaining by dye-cellulase complexes.

Possibilities for Recycling Cellulases After Use in Cotton Processing

Preliminary recycling experiments with cellulase enzymes after cotton treatments at 50°C showed that activity remaining in the treatment liquors was reduced by about 80% after five recycling steps. The potential problems of end-product inhibition, thermal and mechanical deactivation, and the loss of some components of the cellulase complex by preferential and or irreversible adsorption to cotton substrates were studied. End-product inhibition studies showed that the build-up of cellobiose and glucose would be expected to cause no more than 40% activity loss after five textile treatment cycles. Thermal and mechanical treatments of cellulases suggested that the enzymes start to be deactivated at 60°C and agitation levels similar to those used in textile processing did not cause significant enzyme deactivation. Analysis of cellulase solutions, by fast protein liquid chromatography, before and after adsorption on cotton fabrics, suggested that the cellobiohydrolase II (Ce16A) content of the cellulase complex was reduced, relative to the other components, by preferential adsorption. This would lead to a marked reduction in activity after several treatment cycles and top-up with pure cellobiohydrolase II would be necessary unless this component is easily recoverable from the treated fabric.

Effects of Laundering on the Sensory and Mechanical Properties of 1 X 1 Rib Knitwear Fabrics Part I: Experimental Procedures and Fabric Dimensional Properties

Acrylic, cotton, and wool 1 × 1 rib knitwear fabrics have been subjected to up to 50 laundering cycles using a variety of washing and drying conditions. The dimensional, mechanical, and tactile properties of new and washed fabrics are determined and evaluated using standard test procedures. In Part I, we establish the techniques for predicting the final, fully relaxed dimensions of knitted fabrics. We determine fully relaxed k-constant values and the influence of fiber type and washing and drying methods on these values. In Part II, we will discuss the changes in mechanical and tactile properties that occur in these fabrics with repeated washing.