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Journal of Cleaner Production 42 (2013) 167e171

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Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Comparative performance evaluation of conventional bleaching and enzymaticbleaching with glucose oxidase on knitted cotton fabric

Assad Farooq a,*, Shaukat Ali b, Naheed Abbas c, Ghulam Alia Fatima c, Muhammad Azeem Ashraf a

aDepartment of Fibre and Textile Technology, University of Agriculture, Faisalabad, PakistanbDepartment of Chemistry, University of Agriculture, Faisalabad, Pakistanc Institute of Rural Home Economics, University of Agriculture, Faisalabad, Pakistan

a r t i c l e i n f o

Article history:Received 19 July 2012Received in revised form12 October 2012Accepted 15 October 2012Available online 9 November 2012

Keywords:EnzymesBleachingHydrogen peroxideGlucose oxidaseTextile processing

* Corresponding author. Tel.: þ92 3006628872; faxE-mail address: assadfarooq@googlemail.com (A. F

0959-6526/$ e see front matter � 2012 Elsevier Ltd.http://dx.doi.org/10.1016/j.jclepro.2012.10.021

a b s t r a c t

The present research involves the enzymatic bleaching of cotton knitted fabric by using glucose oxidase.The performance of the enzymatic bleaching was compared with conventional bleaching process. Theenzymatic bleaching technique was found to be better technique than conventional one with respect tothe whiteness in addition to comparable mechanical properties like tensile strength and tear strength. Anincrease of approximately 6% was observed in the fabric whiteness index; however the decrease intensile strength is negligible. Furthermore, it was found that hydrogen peroxide produced by glucoseoxidase is a good alternative of commercially available hydrogen peroxide that is currently the mostextensively used bleaching agent in textile processing industry.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

The woven or knitted cotton fabrics contain impurities like oil,stains, waxes and colored matter which influence quality of thedyeing process. These impurities are usually removed by scouringtreatments. The greyness of cotton fabrics is because of the pres-ence of natural pigments in the fibers. In order to obtain brightsubstrate for dyeing or printing and to make fabric uniformly waterabsorbent, a pre-treatment such as bleaching is essential. Bleachingis a chemical process that removes colors, whitens or disinfectsoften via oxidation (Niaz et al., 2009).

Bleaching agents that are extensively utilized in the conven-tional bleaching process may comprise of the chemicals, likesodium chlorite and hypochlorite, formic acid, sodium nitrate andperoxides. These chemicals obviously have numerous disadvan-tages including production of toxic fumes, high time and energyconsumption, fabric strength reduction and environmentalcontamination (Gursoy and Hall, 2001).

Hydrogen peroxide is the most frequently used oxidativebleaching agent for cotton and cotton blends. Hydrogen peroxide

: þ92 41 9201267.arooq).

All rights reserved.

delivers a high degree of whiteness which is stable and does nottend to become yellowish during storage. Moreover, hydrogenperoxide has the advantages of being low cost, flexibility of appli-cation and the possibility of a one-bath (scour/bleach) procedure.On the other hand high temperature bleaching under alkalineconditions necessitates elevated energy utilization and more seri-ously it can cause considerable fiber damage. Different solutionslike the use of bleach activators have been tried to overcome suchproblems (Gursoy et al., 2004; Lim et al., 2005).

Enzymes are biological catalysts so as to be exercised on a largelevel for more than 75 years. Enzymatic handling of textiles isa general practice in textile industry to attain specific finishingeffects. Bio-finishing or bio-polishing is a name employed to illus-trate the elimination of surface fuzz from cellulosic fibers withcellulases. Enzymatic removal of these fibrils end results insmoother, softer and cleaner looking stuffs. Similarly, enzymes arebeing used in the denim industry instead of pumice stones toproduce the old fade look to the denim garments (Shahbaz et al.,2005). Enzymatic dealing of textiles has been accepted for severalyears in the textile wet processing areas. The previous decade haswitnessed an increase in the practice of enzymes because of theirenvironmental friendliness (Cavaco-Paulo and Gubitz, 2003).

Peroxidase, laccase, glucose oxidase, hemi-cellulase and catalaseare instance of the enzymes that possibly will be utilized in the

Table 1Specifications of fabrics.

Composition Type offabric

Type ofKnit

Yarn count(tex)

Course density(cm�1)

Wale density(cm�1)

Area density(g/m2)

Thickness(mm)

Tightnessfactor

Whiteness

100% cotton SingleJersey

Plain 20 7.4 6.3 88 0.39 8.10 15.46

A. Farooq et al. / Journal of Cleaner Production 42 (2013) 167e171168

bleaching process (Jensen, 1998). Commercially accessiblehydrogen peroxide is chemically manufactured; it is capable ofotherwise produced by the oxidation of glucose catalyzed byglucose oxidase.

Glucose oxidase (GOX) from Aspergillus niger is a glycoproteinwhich consists of two identical subunits with two FAD co-enzymes.The enzyme is originated in certain fungi, such as Aspergillus niger,Aspergillus oryzae, Penicillium amagasakiense. Its catalytic producthydrogen peroxide acts as anti-fungal and anti-bacterial (Wonget al., 2008). The enzyme is very specific for b-D-glucose and isable to produce hydrogen peroxide in the incidence of oxygen inaqueous solution by means of b-D-glucose as substrate (Buschle-Diller et al., 2001a).

Glucoseþ O2/Gluconic acidþ H2O2

b-D-glucose is oxidized to gluconic acid through the relocationof two electrons from the substrate (Bankar et al., 2009). Thegenerated hydrogen peroxide is capable of acting as bleachingagent for disintegration of any coloring composites in cotton orother cellulosics. The gluconic acid produced with the oxidation ofb-D-glucose also acts as chelating agent for metal ions and the useof additional stabilizer may be avoided (Tzanov et al., 2002).

Bleaching of cotton fabric by hydrogen peroxide produced fromglucose oxidase has been reported in literature (Tzanov et al., 2002;Eren et al., 2009; Anis et al., 2008, 2009) with comparable resultswith the conventional bleaching. The most important parametersfor bleaching with glucose oxidase are sufficient aeration durationproduction of hydrogen peroxide, pH and temperature. Consider-able increase in the production of hydrogen peroxide was observedby supply of aeration than mechanical agitation technique.Whiteness index of fabric increased initially by increasing theglucose amount up to some extent and than decreased verysignificantly (Tzanov et al., 2001).

The discoloration of cotton fabrics was observed (Shin et al.,2004) during enzymatic bleaching with glucose oxidase due toremaining glucose after reaction. High concentration of glucoseoxidase enzyme and increase in incubation time may be useful foreliminating the problem of discoloration (Saravanan et al., 2010).

The major objective of this project was to assess the perfor-mance of conventional bleaching process against enzymaticbleaching particularly with glucose oxidase and their effect on thequality of cotton fabric. This improvement was measured in termsof physical and mechanical testing of fabric by coping with theindustrial demands which includes no reduction of capacity,reduction of costs and the quality level has to be at-least as good asconventional production.

Table 2Recipe for production of hydrogen peroxide by using enzymeglucose oxidase.

Parameters Values

D-glucose (g/l) 10Glucose oxidase (U/mL) 25Sodium acetate (M) 0.1Temperature (�C) 37pH 5.0

2. Experimental

The research work entitled “Comparative performance evalua-tion of conventional bleaching and enzymatic bleaching withglucose oxidase on knitted cotton fabric” was carried out jointly inDepartment of Fiber and Textile Technology, Institute of RuralHome Economics, Department of Chemistry, University of Agri-culture, Faisalabad and Amtex Pvt Limited Faisalabad.

2.1. Materials

Sodium hydroxide (NaOH, 50%) and Hydrogen peroxide (H2O2,50%) of commercial grade were obtained from Sitara ChemicalIndustries Ltd, Pakistan. D-glucose, D-gluconic acid, Glucose oxidase,Sodium acetate, Acetic acid; Peroxide activator (Magnesiumsulphate) and Nonionic surfactant (Triton X-100) were purchasedfrom SigmaeAldrich. Nonionic & silicone free wetting agent (San-dozin MRN) and anionic stabilizer (SIFA liq) were obtained fromClariant. Samples of pure cotton Knitted fabric were collected fromthe running stock of Amtex Limited Faisalabad, Pakistan having thespecifications as given in Table 1.

2.2. Scouring and demineralization

For scouring, cotton fabric samples were treated with anaqueous solution containing 2.5 g/L NaOH (50%) and 1mL/Lwettingagent (Sandozin MRN) using a material to liquor ratio of 1: 50 at90 �C for 30 min. The bath was then allowed to cool at lowtemperature. The samples were then taken out from the bath andwashed in hot water.

Acidic demineralization of fabric sample was performed bytreating scoured cotton samples with 5 g/L D-gluconic acid at 60 �Cfor 20 min using a liquor ratio of 1:50. Then samples were washedthoroughly with water.

2.3. Production of hydrogen peroxide by using enzyme glucoseoxidase

Hydrogen peroxide was generated by means of glucose asa substrate and glucose oxidase as a catalyst. Glucose dissolved ina pH adjusted 0.1 M phosphate buffer was treated with glucoseoxidase under aeration. The 50 ml medium was prepared in theErlenmeyer flasks consisted of D-glucose, glucose oxidase and 0.1 Mof sodium acetate at pH 5.0. The assays were performed at 37 �Cwith an agitation speed of 100 rpm. The recipe for production ofHydrogen peroxide by using enzyme glucose oxidase is given inTable 2.

The concentration of hydrogen peroxide produced by glucoseoxidase was determined by AATCC test method 102: Determinationof hydrogen peroxide by potassium permanganate titration(AATCC, 2010a).

2.4. Bleaching

After the pre-treatments, i.e. scouring and acid demineralizationboth commercially available and glucose oxidase produced

Table 3Different variables for bleaching fabric samples.

Bleaching agents Duration (min.) Temperature (�C)

A1 ¼ Hydrogen peroxide D1 ¼ 30 T1 ¼ 30A2 ¼ Glucose oxidase D2 ¼ 45 T2 ¼ 60

D3 ¼ 60 T3 ¼ 90

A. Farooq et al. / Journal of Cleaner Production 42 (2013) 167e171 169

hydrogen peroxide were used to bleach the fabric samplesaccording to the bleaching variables given in Table 3.

2.4.1. Bleaching with commercially available hydrogen peroxideThe scoured and demineralized samples were put into the

bleaching baths prepared according to the recipe mentioned inTable 4. The bleaching was carried out for 30 min, 45 min, and60 min at 30 �C, 60 �C, and 90 �C. The stirring was continuouslydone by glass rod to ensure the uniform bleaching. After therequisite time cooling was allowed and samples were taken out ofthe bleaching baths. The samples were washed twice in hot andcold water and dried (Hashem, 2007).

2.4.2. Bleaching with hydrogen peroxide produced by glucoseoxidase

The scoured and acid demineralized samples were placed in thebleaching bath containing hydrogen peroxide produced fromGlucose oxidase and D-glucose at pH 5 and temperature 30 �C withliquor ratio of 1:20. Afterward the pH was changed to 10. Peroxideactivator and nonionic surfactant were also added. Treatmentswere then performed at different temperatures (30 �C, 60 �C, and90 �C) for different times (30 min, 45 min, and 60 min). The fabric

Table 5Recipe for bleaching with hydrogen peroxide produced by glucoseoxidase.

Parameters Values

Glucose oxidase (U/ML) 25D-glucose (g/L) 10Peroxide activator (g/L) 2Nonionic surfactant (mL/L) 1Temperature (�C) 30, 60, 90Time (min) 30, 45, 60

Table 6Comparison of individual treatment means.

Fabric whiteness Fabric tensile strength (lb)

Bleaching agent Temperature Duration Bleaching agent Temp

A1 ¼ 47.44b T1 ¼ 26.19c D1 ¼ 46.82c A1 ¼ 68.10a T1 ¼ 6A2 ¼ 50.58a T2 ¼ 54.79b D2 ¼ 48.90b A2 ¼ 67.70b T2 ¼ 6

T3 ¼ 66.08a D3 ¼ 51.38a T3 ¼ 6

Any two means not sharing a letter (a, b, c) in common differ significantly at 0.05 level ofmean value.

Table 4Recipe for bleaching with commercially available hydrogen peroxide.

Parameters Values

Liquor ratio 1:20Hydrogen peroxide (mL/L) 10Sodium hydroxide (mL/L) 6Stabilizer (mL/L) 1Wetting agent (mL/L) 1Temperature (�C) 30, 60, 90Time (min) 30, 45, 60

samples were then rinsed, and the enzyme solution discarded. Thesamples were neutralized with dilute acetic acid, washed in water,and then air dried. The recipe for bleaching with hydrogen peroxideproduced by glucose oxidase is given in Table 5.

2.5. Fabric evaluation

After all treatments following tests are carried out to check thebleaching performance on cotton knitted fabric samples:

2.5.1. Fabric whitenessThe whiteness of the bleached samples was measured on

Datacolour Spectra flash SF600 CT-Plus according to AATCC testmethod 110-2005 for whiteness measurement of textiles (AATCC,2010b). It is the latest laboratory equipment which is principallyemployed for whiteness checking, colour and shade matching.

2.5.2. Tensile strengthThe tensile strength of a fabric was determined by the

maximum force to break the fabric. The testing was performed ontensile testing machine based on constant rate of elongationaccording to ASTM standard test method D-5034 (ASTM, 2010a).

2.5.3. Tear strengthThe force needed to initiate or to continue tearing fabric is

known as tear strength. It is the resistance of a material to a forcetending to tear it apart, measured as the maximum tension thematerial be able to withstand exclusive of tearing. ASTM standardtest method D-2261 for tearing strength of fabric was used formeasurement (ASTM, 2010b).

2.5.4. Statistical evaluationThe results were statistically analyzed using DMR test for indi-

vidual comparison of means (Steel et al., 1997).

3. Results and discussion

The single jersey knitted cotton fabrics were bleached usingcommercially accessible hydrogen peroxide and enzymaticallygenerated hydrogen peroxide at different levels of time andtemperature as given in Table 3. The effects of time and tempera-ture on the bleaching of single jersey fabric were observed bycalculating means. After bleaching, the fabric samples were testedfor whiteness index, tensile strength and tear strength in order toevaluate bleaching performance.

3.1. Whiteness index

The statistical comparison of individual means for whitenessindex is presented in Table 6, which indicates that the maximumwhiteness index was achieved for A2 (Enzymatic bleaching agent)with the mean value 50.58 followed by A1 (Conventional bleachingagent) with mean value 47.44. The present results confirm thebetter performance of the enzymatic bleaching agents in

Fabric tear strength (lb)

erature Duration Bleaching agent Temperature Duration

9.69a D1 ¼ 7.97b A1 ¼ 6.94b T1 ¼ 7.89a D1 ¼ 7.52a7.97b D2 ¼ 8.14a A2 ¼ 7.51a T2 ¼ 7.32b D2 ¼ 7.12b6.05c D3 ¼ 7.79c T3 ¼ 6.48c D3 ¼ 7.04c

probability. Further small letters (a, b, c) are placed according to increasing order of

01020304050607080

30 °C 60 °C 90 °C

Temperature

Wh

iten

ess in

dex

30 min 45 min 60 min

Fig. 1. Performance of conventional bleaching agent with respect to whiteness index.

64

65

66

67

68

69

70

30 °C 60 °C 90 °CTemperature

Te

ns

ile

s

tre

ng

th

(lb

)

30 min 45 min 60 min

Fig. 3. Performance of convention bleaching agent with respect to fabric tensilestrength.

A. Farooq et al. / Journal of Cleaner Production 42 (2013) 167e171170

comparisonwith conventional bleaching agent. These results are inline with the findings of Buschle-Diller et al. (2001b) who proposedthat enzymatic hydrolyzes of carbohydrates results in betterbleaching action. Similarly, the fabrics bleached with enzymaticbleaching agent are softer than the fabrics bleached with conven-tional bleaching agents. Studies affirmed that the enzymaticscouring and bleaching of cotton fabrics develop softness andapproximately the similar whiteness contrasted to the conven-tional one (Mangovska et al., 2004). Enzymatic treatment of cottonpeels off the cellulose which results in the formation of more pol-ished surface (Ramadan, 2008). Gluconic acid produced in thereaction acts as a chelator for metal ions so the use of additionalstabilizing agent may be avoided. In a previous work it hasobserved that glucose remaining after the reaction stabilizes thehydrogen peroxide (López and Cavaco-Paulo, 2008) and may causesome discoloration.

Figs. 1 and 2 reveal the performance of both conventional andenzymatic bleaching agents at variable time and temperatures asmentioned in Table 3. The results explained that for both conven-tional and enzymatic bleaching, whiteness index was increased byincreasing the temperature. Similarly, the trend is evident that withthe increase in bleaching duration whiteness index also increased.Researches unraveled that whiteness was augmented by increasingthe concentration and temperature (Rekha, 2002). MoreoverCsiszar et al. (2007) reported that depending on bio-treatmentinterval, the whiteness possibly can be increased up to 10%.

3.2. Tensile strength

The statistical comparison of individual treatment means withregards to tensile strength of fabric is accessible in Table 6. Thecomparison of individual means showed that the maximum tensilestrength was documented for A1 (Conventional bleaching agent)with the mean value 68.10 lbs followed by A2 (Enzymatic bleaching

01020304050607080

30 °C 60 °C 90 °C

Temperature

Wh

iten

ess in

dex

30 min 45 min60 min

Fig. 2. Performance of enzymatic bleaching agent with respect to whiteness index.

agent) with mean value 67.70 lbs. The end results illustrated thattensile strength was a little greater for conventional bleaching. Thisdecrease in tensile strengthmay be due to decrease in the degree ofpolymerization of cellulose in result of oxidation (Tzanov et al.,2001; Buschle-Diller et al., 2001a). In a previous study, thecurrent results were also instituted in order with previous findingsthat the capacity of various enzymes to perk up the surface wettingproperties of raw and pre-treated cotton fabrics (Hartzell andHsieh, 1998).

Figs. 3 and 4 reveal the tensile strength of the fabrics treatedwith both conventional and enzymatic bleaching agents at variabletime and temperatures. The results show that tensile strength wasdecreased by increasing the temperature. The present findingswere verified by the exploration of previous studies which revealedthat lower temperatures during pre-treatments result in greatertensile strength (Shenai, 1996). Moreover, the bleaching durationhas abrupt effect on the tensile strength and D2 (45min) is themostappropriate bleaching duration to retain maximum tensilestrength. These findings were also seasoned by the research workof Pereira et al. (2005) who concluded that strength of fabric isexaggerated by the variation in treatment time.

3.3. Tear strength

The statistical comparison of individual treatment means withregards to tear strength of fabric is presented in Table 6. Thecomparison of individual means proved that the maximum tearstrength was traced for A2 (Enzymatic bleaching agent) with themean value 7.51 lbs followed by A1 (Conventional bleaching agent)with mean value 6.94 lbs. The results proved that tear strength wasa little bit greater for enzymatic bleaching.

Figs. 5 and 6 reveal the performance of both conventional andenzymatic bleaching agents for tear strength of the fabric at vari-able time and temperatures as mentioned in Table 3. The resultsshows that tear strength were decreased by increasing the

62

64

66

68

70

72

30 °C 60 °C 90 °C

Ten

sile

stren

gth

(lb

)

Temperature

30 min 45 min 60 min

Fig. 4. Performance of enzymatic bleaching agent with respect to fabric tensilestrength.

0

2

4

6

8

10

30 °C 60 °C 90 °C

Temperature

Te

ar s

tre

ng

th

(lb

)

30 min 45 min 60 min

Fig. 5. Performance of convention bleaching agent with respect to fabric tear strength.

0

2

4

6

8

10

30 °C 60 °C 90 °C

Temperature

Tea

r stren

gth

(lb

)

30 min 45 min60 min

Fig. 6. Performance of enzymatic bleaching agent with respect to fabric tear strength.

A. Farooq et al. / Journal of Cleaner Production 42 (2013) 167e171 171

temperature. The elevated temperature and relative movementflanked by fabric and water all through pre-treatment produce aneffect that throw in to fabric surface irregularities and its suc-ceeding wear attributes (Hasani, 2010). However, for time durationthe trend is apparent that with the increase in bleaching durationtear strength of the fabric reduces.

4. Conclusion

� The enzymatic bleaching technique was found to be bettertechnique than conventional one with respect to the whitenessin addition to comparable mechanical properties like tensileand tear strength. Moreover, the fabrics bleached with enzy-matic agents were softer and hence will have better comfortproperties.

� From the overall results, it can be concluded that hydrogenperoxide produced by glucose oxidase may be a good alterna-tive of commercially available hydrogen peroxide that iscurrently the most extensively used bleaching agent inconventional bleaching process.

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