Jin, Chunhua
ABSTRACT
Ramie fabrics after weaving and desizing are treated with three kinds of commercial enzyme mixtures to examine the changes in some fabric properties compared with an alkaline boiled treatment. The effects of the enzymes on removing pectin from ramie are evaluated. Relative amounts of residual pectic substances on the surfaces of untreated and treated fabrics are obtained by staining with ruthenium red. The content of pectic substances in the fibers after treatments is measured as galacturonic acid by a carbazole-- sulfuric acid reaction, then the results are related to changes in whiteness, surface structure observed by SEM photographs, and mechanical properties measured by the KES-FB.
Recently, many studies of enzyme applications on textiles have been reported. Some were studies of cellulase hydrolysis of cellulosic materials and the textile properties of cotton fabrics subjected to cellulase treatment [4, 14, 17]. In addition, other studies reported biopolishing of cotton fabrics, which depresses pill formation and improves fabric hand [16], and enzyme applications for scouring cotton fabrics to reduce impacts on the environment through reduced energy cost and waste water pollutants using biochemical reactions under mild conditions [5, 10-12, 19]. Pectinase enzyme complexes are capable of breaking down pectic substances and related compounds into water-soluble fragments. Li et al. treated raw cotton fibers and unscoured cotton fabrics with pectinases and cellulases and found that significant changes occurred in cotton fiber and fabric properties under mild treatment conditions [10-12].
Bast fibers such as linen and ramie contain less cellulose and more noncellulosic materials like pectic substances, hemicellulose, lignin, wax, natural color, and so on, than cotton fibers. Because cellulose fibers are bound by pectic substances, retting or alkaline boiling of the raw materials must first occur to prepare the fibers before weaving. Recently, many studies have reported on enzyme retting of flax [1, 2, 7, 8]. However, in another study, pectic substances still remained in bleached linen [7]. Ramie has a high potential use not only for clothing materials, but also for industrial composite materials [18], so other workers have attempted to improve its mechanical properties such as harsh and rigid handle and poor elastic recovery [6]. Scoured and spun ramie fabrics still contain noncellulosic materials, which affect its properties.
In this paper, we examine the effects of commercial enzyme mixtures, mainly from pectinase, cellulase, and hemicellulase, on removing pectic substances from ramie fabric, and we try to evaluate the effects of pectinase and cellulase. In addition, we evaluate resulting effects such as changes in whiteness, surface structure, and mechanical properties compared with fabrics treated by alkaline boiling.
Experimental
Twill-woven ramie fabric supplied by Kurabo Co. Ltd. was desized in distilled water for 30 minutes at 75 deg C and then washed with deionized water. Three kinds of commercial enzyme mixtures in cultivation solution were supplied by Novo Nordisk Co. Ltd.: Ultrazyme 40L consists of pectintranseliminase, polygalacturonase, pectinesterase, hemicellulase; Viscozyme L consists of various kinds of carbohydrates such as arabanase, cellulose, beta-glucanase, hemicellulase, and xyranase, etc.; and Cellsoft L, which consists of cellulose obtained from Trichoderma and is used for biopolishing cellulosic fabrics.
To prepare an enzyme solution, 0.3 g enzyme solution was dissolved in 1000 ml cold 0.05 M sodium acetate buffer (pH 4.6). A sheet of fabric with 10 g weight was treated in the solution at a liquor ratio of 1:100 for 1 hour at 50 deg C using a Terg-O-Tometer (Ueshima Seisakusho Ltd.) with mechanical agitation. To terminate the reaction, the fabrics were washed with deionized with water five times before air-drying. Alkaline boiling involved a 4% aqueous sodium hydroxide solution at the boil at a liquor ratio of 1:100 for 1 hour. Then the treated fabrics were rinsed with deionized water five times and dried.
Both untreated and treated fabrics were stained in a ruthenium red aqueous solution. Surface reflectance R was measured with a spectrophotometer (Minolta CM-- 2002). K/S values were calculated according to the Kubelka-Munk equation [20]. The function K/S was directly proportional to the concentration of colorant in the substrate.
The pectic substances in the ramie fabrics were extracted with 0.5% aqueous ammonium oxalate for 1 hour at 90 deg C and measured as garacturonic acid by a carubazol-sulfuric acid reaction [3, 13]. The amount of pectic substances was evaluated as 1.37 times the garacturonic acid.
Lightness L* and yellowness b* based on CIE L*a*b* color space for the untreated and treated fabrics were measured using a spectrophotometer (Minolta CM-- 2002).
For the SEM observations, samples (8 mm X 8 mm) were mounted on SEnt stubs, coated with 30 nm of gold in a sputter-coater (Nippon Denshi JFC- 1100), and observed with a scanning electron microscope (Nippon Denshi JSMT-300, 25kV).
Mechanical properties such as tensile, shearing, bending, and compression were measured with a KES-FB instrument (Kato Tech Co.) in the manner described elsewhere [9], and the results are summarized in Table II. The parameters measured for the tensile property were linearity of the tensile curve (LT), tensile energy per unit area (WT), tensile resilience (RT, and maximum elongation (EMS. The parameters measured for the shearing property were shearing stiffness (G), hysteresis at 0.50 shearing angle (2HG), and hysteresis at 5 deg shearing angle (2HG5). The parameters measured for the bending property were bending rigidity per unit width (B) and hysteresis of the bending moment at 0.5 cm^sup -1^ of curvature (2HB). The parameters measured for the compression property were the linearity of compression curve (LC), compression energy (WC), and compression resilience (RC). The thickness under the compression load 0.5 gf/cm^sup 2^ and the weight of fabrics after treatment per unit area before treatment were also measured and are summarized in Table II. We conditioned the test specimens at standard conditions (20 deg C, 65% RH) before measuring these properties.
Results and Discussion
EVALUATING PECTIC SUBSTANCES ON AND IN FIBERS
Because the removal of pectic substances is an important issue in scoring ramie, we evaluated the relative amount of residual pectic substances in the fabric by K/S value of fabrics stained with ruthenium red. Because the residual pectic substances of untreated fabric were highest among them, this was taken as 100% (Table I). Alkaline boiling reduced pectic substances on the fibers by about 40%. The effects of three kinds of the enzyme mixtures were different. The effect of the viscozyme treatment was nearly the same as that of alkaline boiling. The effect of Cellsoft was highest among them; in contrast, that for Ultrazyme was lowest.
The rate of pectic substances in the fibers after treatment, measured by extraction by 1% aqueous ammonium oxalate, are also summarized in Table I. Apparently the amount of pectic substances in the Ultrazyme-treated fiber was lowest. Note however, that all pectic substances could not be extracted under the experimental conditions used, and some of them still remained in the fibers. The reason for the larger values of treated fabrics, except for Ultrazyme, than for untreated fabrics is because the treated fabrics simultaneously lost other components such as cellulose, hemicellulose, lignin, and so on. Thus the rate of pectic substances in the fibers became higher than the untreated one.
CHANGES IN L* AND b*
In order to evaluate changes in whiteness with scouring treatment, we measured the lightness (L*) and yellowness (b*) of the CIE L*a*b* color space. There was a small increase in L* and a small decrease in b* for the fabrics treated with alkaline boiling, Viscozyme, and Cellusoft (Table I), which means that the whiteness of the fabrics increased, although the ramie fabrics were white originally. On the other hand, both L* and b* decreased significantly for the sample treated with Ultrazyme, which means fabric whiteness decreased and the hue of the fabric changed somewhat. These results coincide with high amounts of pectic substances on the fiber surface.
SEM OBSERVATIONS OF SURFACE STRUCTURE
We observed morphological changes from treatment using a scanning electron microscope (SEM). The SEnt micrographs are shown in Figure 1. The fiber structure of the untreated fabric had clean surfaces covered with lamella and many striations along the fiber axis (A). Alkaline boiling created a large amount of loose fibrils on the fiber surface and deeper striations along the fiber axis (B). On the other hand, Ultrazyme treatment acted on the fiber surface and degraded the lamella, causing parts of them to drop off the surface (C). Vicsozyme acted more vigorously than Ultrazyme on the fiber surface and degraded the lamella. Nodes were distinguished clearly on the Ultrazyme-treated fiber (D). The surface of the Cellusoft-treated fiber was very clean. Most fibrillar fuzz was removed from the surface, and as a result, nodes and striations were clearly distinguishable (E). Mori et al. treated cotton fibers with cellulase and reported that the inner structure of the fibers was degraded during cellulase treatment [14]: Buschle-Diller et al. investigated cellulase hydrolysis of ramie with the other cellulose fibers and concluded that the cotton, linen, and ramie fabrics manifest the desired effect of surface fibril removal without suffering large weight losses or reductions in tensile strength after short treatment periods [4]. Although an hour treatment with cellulase just peeled off the lamella of the ramie fiber in this work, longer treatment times might cause more damage to the inner structure of the ramie.
MECHANICAL PROPERTIES MEASURED By KES-FB
From the results of the tensile properties, we saw an increase in EMT and WT for alkaline treatment but not for enzyme treatment. This means that the alkaline treatment swelled the fibers, so they became easier to stretch and needed more energy to stretch to the maximum load of 500 gf/cm. The decrease of 2HG5 indicated increased elasticity [9, 15]. An increase in thickness despite fabric elongation (warp 2.56%, weft 0.84%) coincided with this. In contrast, there was a decrease in WT and a small increase in G for the Ultrazyme treatment. This means the treatment made the fibers stiffer and less elastic. In addition, the larger values of 2HG and 2HG5 also mean the Ultrazyme treatment made the fabrics slightly elastic. The thickness was nearly the same as that of the untreated fiber despite shrinkage by the treatment (warp 3.21 %, weft 2.94%). The decrease in weight per unit area of fabrics was largest with the Ultrazyme treatment, which must have been caused by the vigorous action of the pectinase. We expected a change in bending stiffness with the scouring treatment, but there was no significant change. The increase in 2HB just for Cellusoft indicated decreased elasticity as well as increased 2HG and 2HG5 and decreased WC. The weight loss observed with the treatment must have been caused by the action of cellulase on the fiber surface. The decreased thickness may have been caused by both removal of fibrillar fuzz from the surface and a small elongation with treatment (warp 1.47%, weft 0.42%). The change in mechanical properties with Viscozyme treatment was smallest among them.
Conclusions
We have treated ramie fabrics with three kinds of commercial enzyme mixtures and evaluated the scouring effects on pectic substance removal, whiteness, surface structure and mechanical properties compared with alkaline boiled samples. Cellusoft, made from cellulase, acts on the surface of the fibers and removes fibrillar fuzz from the surface. At the same time, the pectic substances on the surface are removed. In contrast, treatment by Ultrazyme, consisting mainly of pectinase, shows drastic effects on the removal of pectic substances in the fibers, but removal is less than that by cellulase, resulting in decreased whiteness for Ultrazyme-treated fabrics.
Measurements of mechanical properties with KES-FB reveal that untreated and treated ramie fabrics are still stiff with low elongation. However, there is a small change, that is, alkaline treatment swells the fibers and makes them easier to stretch. On the other hand, enzyme-- treatment makes the fibers stiffer and less elastic. The effect is larger in the order Ultrazyme > Cellusoft > Viscozyme.
ACKNOWLEDGMENTS
We would like to thank Kurabo Co. Ltd. for supplying the ramie fabric and Novo Nordisk for providing the enzymes for this research.
Literature Cited
1. Akin, D. E., Morrison, W. H., Gamble, G. R., Rigsby, L. L., Henriksson, G., and Eriksson, K-E. L., Effect of Retting Enzymes on the Structure and Composition of Flax Cell Walls, Textile Res. J. 67(4), 279-287 (1997).
2. Akin, D. E., Rigsby, L. L., and Perkins, W., Quality Properties of Flax Fibers Retted with Enzymes, Textile Res. J. 68(10), 747-753 (1999).
3. Bitter, T., and Muir, H. M., A Modified Uronic Acid Carbazole Reaction, Analy. Biochem. 4, 330-334 (1962).
4. Buschle-Diller, G., Zeronian, S. H., Pan, N., and Yoon,
M. Y., Enzymatic Hydrolysis of Cotton, Linen, Ramie, and Viscose Rayon Fabrics, Textile Res. J. 64(5), 270-279 (1994).
5. Buschle-Diller, G., Mogahzy, Y. E., Ingresby, M. K., and Zeronian, S. H., Effects of Scoring with Enzymes, Organic Solvents, and Caustic Soda on the Properties of Hydrogen Peroxide Bleached Cotton Yam, Textile Res. J. 68(12), 920-929 (1998).
6. Cheng, K. P. S., and How, Y. L., Modifying the Mechanical Properties of Ramie and Its Blends, Textile Res. J. 66(4), 209-214 (1996).
7. Dezert, M-H., Viallier, P., and Wattiez, D., Continuous Control of an Enzymatic Pretreatment on Linen Fabric Before Dyeing, J. Soc. Dyers Colour. 114(10), 283-286 (1998).
8. Henriksson, G., Akin, D. E., Rigsby, L., Patel, N., and Eriksson, K-E. L., Influence of Chelating Agents and Mechanical Pretreatment on Enzymatic Retting of Flax, Textile Res. J. 67(11), 826-836 (1997).
9. Kawabata, S., "The Standardization and Analysis of Hand Evaluation," 2nd ed., Textile Machinery Society of Japan, Osaka, 1980.
10. Li, Y., and Hardin, I. R., Enzymatic Scouring of Cotton: Effects on Structure and Properties, Textile Chem. Color. 29, 71-76 (1997).
11. Li, Y., and Hardin, I. R., Treating Cotton with Cellulases and Pectinases: Effects on Cuticle and Fiber Properties, Textile Res. J. 68(9), 671-679 (1998).
12. Li, Y., and Hardin, 1. R., Enzyme Scoring of Cotton-- Surfactants, Agitation, and Selection of Enzymes, Textile Chem. Color. 30(9), 23-29 (1998).
13. McComb, E. A., and McCready, R. M., Colorimetric Determination of Pectic Substances, Analyt. Chem. 24(10), 1630-1633 (1952).
14. Mori, R., Haga, T., and Takagisi, T., Bending and Shear Properties of Cotton Fabrics Subjected to Cellulase Treatment, Textile Res. J. 69(10), 742-746 (1999).
15. Pan, N., Zeronian, S. H., and Ryu, H-S., An Alternative Approach to the Objective Measurement of Fabrics, Textile Res. J. 63(1), 33-43 (1993).
16. Pedersen, G. L., Screws, G. A., and Cedroni, D. M., BioPolishing von Cellulosetextilien, Melliand Textilber. 74(12), 1277-1280 (1993).
17. Radhakrishnaiah, P., Meng, X., Huang, G., Buschle-Diller, G., and Walsh, W. K., Mechanical Agitation of Cotton Fabrics During Enzyme Treatment and Its Effect on Tactile Properties, Textile Res. J. 69(10), 708-713 (1999).
18. Ruegg, J., and Colijin, J., Ramie-Hochleistungsfaser aus der Natur, Textilveredlung 29, 9-13 (1994).
19. Sawada, K., Tokino, S., Ueda, M., and Wang, X. Y., Bioscouring of Cotton with Pectinase Enzyme, J. Soc. Dyers Color. 114(11), 333-336 (1998).
20. Trotman, E. R., Dyeing and Chemical Technology of Textile Fibers, Charles Griffin & Co. Ltd, London, 1975. Manuscript received September 13, 2000; accepted December 12, 2000.
CHUNHUA JIN AND MASAKO MAEKAWA1
Division of Life Science and Human Technology, Nara Women's University, Nara 630-8506, Japan
1 Author to whom correspondence should be addressed. Division of Life Science and Human Technology, Nara Women's University, Nara 630-8506, Japan, phone & fax: 0742 (20) 3467, email: maekawa@cc.nara-wu.ac.jp.
