| In the production process of ramie, ramie degumming is an important part of this production process. However, the traditional warm water retting method has some disadvantages, such as long degumming time and low yield. Comparing with chemical alkali cooking method, biological technology uses degumming fermentation method of retting bacterial and exploits the synergy of pectinase, semi fiber enzymes and other enzymes to degrade the gum absorbed on ramie phloem. This method not only make the fiber ramie achieve the textile requirement, but also retain the inherent fiber morphology. Therefore, biological technology has broad prospects in the hemp degumming. Screening and mutating the degumming bacterial, which has completing enzyme system and high active enzyme and is suitable for industrialized production, has been the main research direction of the biological degumming of ramie.Engineering Research Center for Clean Production of Textile Printing, Ministry of Education, Wuhan Textile University, select high performance single degumming bacterial L11 by screening dominant strains from ramie degumming symbiotic bacteria RAMCD407 in the course of study on ramie biological degumming. This paper further studied the fermentation conditions of strain L11 for biological degumming and researched the ultraviolet mutagenesis of strain L11.(1) Use the screened single strain of bacillus cereus L11 to ramie degum, record the growth of microbial in fermentation liquid and the change rules of PH, reducing sugar, enzyme activity, chemical oxygen demand(COD), protein and the residual gum rate of organic matter in the fermentation degumming process. The results show that the residual gum rate decreases greatly in the early period of degumming, flattens out in the middle period and decreases sharply again in the late periods of degumming with the lowest value 15.86%. The quantity of live degumming bacteria increases continually in the early and middle periods of degumming and tends to decrease in the late period. The enzyme activity of pectinase and xylanase increases slowly in the early period, increases rapidly in the middle period and tends to decrease in the late period of degumming. The enzyme activity of cellulose is very low and changes little in the degumming process. The enzyme activity of pectinase and xylanase respectively is 118.48 U/m L and 61.26 U/m L. The p H value decreases in the early and middle period and increases in the late periods, getting the lowest value 6.91 at 36hours, like a “V” shape. The content of protein firstly increases and then decreases, it shows a peak value 117.33 mg/L. The curve of reducing sugar shows two peak values and varies like an “M” shape. The COD value increases in the early and middle period and decreases in the late period, getting the peak value 15.9 g/L at 48 hours.(2) Use the high performance ramie degumming strain L11 as starting strain of ultraviolet mutagenesis to be irradiated by ultraviolet respectively. It can be found that the best irradiation time is 150 seconds by changing the ultraviolet irradiation time, when the fatality rate of strain is 86.7%. Then fermentation degum the obtained mutant strain, measure the pectinase enzyme activity, cellulose enzyme activity and residual gum rate of mutant strain at regular intervals. By comparing the enzyme activity of fermentation liquid before and after the ultraviolet mutagenesis and the residual gum rate after ramie degumming, it can be found that the pectinase enzyme activity increases continually and the ramie residual gum rate decreases when the irradiation time is between 30 seconds and 150 seconds. The pectinase enzyme activity gets the maximum value 175.63 U/m L and the residual gum rate gets the minimum value 13.32% when the irradiation time is 150 seconds. This means that when the irradiation time is 150 seconds, the strain obtained through ultraviolet fermentation, which has high pectinase enzyme activity and low residual gum rate, is the high performance degumming strain L12. |
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