Study On The Bleaching Effect Of Glucose Oxidase In Cotton Fabric Pretreatment

As a new enzyme for bleaching purpose,Glucose oxidase is considered to be the most probable bleaching agent used in industrial production abroad.Some interaction and bleaching processes of the enzyme had been studied abroad,but still lack of domestic study and deeply understanding.And in this paper,the bleaching effect of glucose oxidase in cotton fabric pretreatment was studied.Because the whiteness of the cotton fabric is influenced by cotton pigment, fragments of cotton seed coat,and so on,the experiment is started with pigment.After extracted from cotton seed coat with 1%NaOH,the pigment was purified.Basic performance of the pigment was studied.The pigment structure and bleaching process was researched,and it might be not composed of single compound.The main components are polyphenol substance with benzene ring structure,and groups such as carbonyl and ether bonds are also contained in conjugated chromophoric system.In bleaching process,Oxidation is taken place where there are methylene-quinone, carbonyl and ether bonds structures.The pigment then undergoes intramolecular nucleophilic attack of the carbonyl carbon with formation of dioxetanes followed by rearrangement with cleavage of the carbon-carbon bond of the dioxetane ring system. And the product can be degraded further.The optimum bleaching process was fixed through single factor experiments, L₂₅（5⁶） orthogonal experiments and its optimization experiments.H₂O₂ the bleaching needed was first produced at pH 7.0,temperature 40℃with glucose oxidase 10.650U/mL and glucose 15g/L for 100min,the buffer was stirred at 500rpm with ventilation at the speed 4.5g/L.After adjusted the pH to 10.0-10.5,fabrics was bleached at 95℃for 60min with the bath ratio 10:1.And other agents such as stabilizer for H₂O₂ needn’t to be added into the bath.Because H₂O₂ produced by glucose oxidase hadn’t decomposed fully and effectively,whiteness of the glucose oxidase bleached fabric could not catch up with that of fabric bleached in traditional process.But the glucose oxidase bleached fabric has less fiber disruption and strength loss.In order to increase the decomposition rate of the H₂O₂ and low the energy consumption,glucose oxidase bleaching process at low temperature was studied,and the optimum process was fixed.first,glucose oxidase produced needed H₂O₂ at the optimum process circumstances.Then low temperature bleaching process was carried out at pH 7.0,70℃for 60min with sodium pyrophosphate 2g/L and n_TAED/_nH2O2 0.5:1. And the bath ratio was 10:1.Decomposition rate of the H₂O₂ was above 98%in the low temperature bleaching.H₂O₂ could be decomposed fully and effectively.The problem about decomposition rate was solved well.And the process was carried out at neutral pH and low temperature,the ambient pressure be lightened and the energy consumption lowed.It is an ideal bleaching method.The fabric bleached with glucose oxidase has the same whiteness with that bleached in traditional process.And has less fiber disruption and strength lose.Be compared with alkaline scouring process,cotton seed coat fragments are the most resistant impurities in cotton fabric following bioscouring.The incomplete removal of cotton seed coat fragments during bioscouring increases the pressure of the subsequent bleaching process,which remains an obstacle to the commercialization of the bioscouring process.Xylanase was used for cotton fabric pretreatment,the removal rate of cotton seed coat fragments and the effect on whiteness of the fabric bleached with glucose oxidase in low temperature were studied.The fixed optimum xylanase pretreatment process was xylanase 0.8U/mL,at pH 8.0,60℃for 60min with the bath ratio 20:1.Then the pretreated fabric was bleached with glucose oxidase at low temperature.The removal rate of cotton seed coat fragments on xylanase pretreated fabric was lower than that on alkaline processed fabric.The xylanase pretreatment process must be optimized further,for instance,contrapose components and their contents in cotton seed coat,complex enzyme system composed of xylanase and enzymes can be used.Xylanase could remove cotton seed coat fragments partially, and had an active effect on lightening bleaching burden.After pretreated,the fabric bleached in low temperature has the same whiteness with that bleached in traditional process.Compared with glucose oxidase low temperature bleaching,the pretreatment process had some effect on whiteness enhancement,but not so obvious.And the low temperature bleaching process with pretreatment has less fiber disruption and strength lose.