| The enzymes have got more attention and applications for their efficiency, specificity and mild action conditions. However, because most enzymes are proteins, inactivation behavior will take place inevitably at high temperatures. Poor thermostability has become the limitation of applications of enzymes at high temperatures. Therefore, it is very important to study the enzymatic thermostability and explore the methods of improving the thermal resistance of enzymes.Firstly, the thermostability ofα-amylase in solution was studied. The influence of several additives on the thermostability ofα-amylase was discussed. The varieties of particle sizes and fluorescence spectrum in the inactivation process were investigated. The results showed that inactivation of mesophilicα-amylases in solution followed first order kinetics. Calcium acetate, sodium lactate, L-histidine and low molecular weight chitosan (LWCS) could improve the thermostability of the enzymes remarkably. Among these additives, LWCS had best stabilizing effect. The composite of calcium acetate and sodium lactate had positive action on the thermostability ofα-amylase A, which was better than that when the additives was used individually. But the composite did not have such effect on the thermostability ofα-amylase B.α-Amylase aggregated and the particle size was increased at high temperatures. The thermal stabilizers postponed the inactivation through restrained the aggregation of the enzyme. The results from fluorescence spectroscopy measurements showed that the addition of stabilizers changed the conformation of the enzyme and made the enzyme in more ideal status, which was favorable to the thermostability of the enzyme.The inactivation of enzymes occurred on the fabrics in desizing process. The thermostability ofα-amylase on the fabrics was studied. The results showed that the inactivation of the enzyme on the fabrics also followed first order kinetics. But the inactivation rate ofα-amylase on the fabric was much slower than that in solution, which demonstrated that the fabrics were also good thermal stabilizers of the enzyme. After several stabilizers were added, the thermostability was further improved. Especially the addition of LWCS could make theα-amylase obtain preferable thermostability at temperatures higher than 100℃.Influences of various factors on the desizing effect of cotton fabrics were studied by "change-one-factor-at-a-time" method and orthogonal design. The optimal process conditions were set as follows: steaming temperature 100℃, steaming time 15 min,α-amylase B concentration 0.5 g/L, pH=6, LWCS concentration 15 mmol/L. The cotton was desized under this condition and the desizing ratio was 98.6%.The pectinase has obtained more and more application on the scouring of cotton fabric. But the study of the enzyme property is not intensive enough. In this paper, the activity of pectinase for scouring was explored in detail. It could be observed that pectinase A could hydrolyze apple pectin and the product had a characteristic absorption peak at 236 nm in ultraviolet region. Therefore, ultraviolet spectrophotometry method could be used to measure the activity of pectinase A. However, pectinase A had no effect on the pectin in cotton fabrics and this enzyme was not suitable for the souring of cotton fabrics. Pectinase B could not hydrolyze apple pectin and ultraviolet spectrophotometry method could not be applied to measuring its activity. But because pectinase B was able to hydrolyze the pectin in cotton fabrics, its activity could be characterized via the removing ability of pectin of cotton fabrics.The enzymology property and thermostability of pectinase B was investigated. When the concentration of pectinase B was 0.16 g/L, the optimal temperature was 70℃, the optimal pH value was 7-9. Pectinase B had good thermostability at temperatures lower than 70℃, and the half life time at 70℃was 131.2 min.Both the pectin and wax in cotton fabrics had effects on the wettability. And the effect of wax was much deeper than that of the pectin. Therefore, the pectinase and surfactant should be combined to remove pectin and wax at the same time in scouring process. Through "change-one-factor-at-a-time" method and orthogonal design, the optimal souring process conditions were determined as follows: pretreatment (5 min)→2 dip-squeeze (pectinase B 2 g/L, pH=7)→treatming for 30min at 90℃→treating for 20 min in 2 g/L paregal O solution at 100℃→washing thoroughly. After the treatment, the removing ratio of pectin was 93.8%, the capillary effect was 18.4 cm.Lastly, the cotton fabrics were treated by one-bath desizing-scouring method withα-amylase and pectinase and the conditions were optimized and adjusted, which was as follows. Solution (α-amylase B 0.5g/L, pectinase B 1g/L)→2 dip-squeeze (Liquid pickup 100%)→treatming for 20min at 90℃→treating for 20 min in 2 g/L paregal O solution at 100℃→washing thoroughly. Under this condition, the desizing ratio was 96.4%, the removing ratio was 90.4%, and the capillary effect was 18.6 cm.
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