Study On Techniques And Mechanism Of Microbial Retting Of Flax In South China

Flax (Linum usitatissimum L.) is the important raw material for textile fiber in China. The initial step for converting flax to linen is called retting, which is the major problem in processing flax. After introduction of flax to southern China, in order to establish the technical system of new pattern retting of flax in south China, major factors of natural water retting of flax, such as the type and number of retting bacteria, retting-enzymes, external retting conditions and stem characteristics were all studied deeply in the paper. And throuth screening from flax, a bacteria strain with high retting ability was obtained.The main results are as follows:(l)The pectinolytic bacteria played an important role in the retting. The activity of pectinase in retting water had an osculatory correlation with the retting. Water quality, ratio of flax stem to water, pH, water temperature and so on had an important effect on the growth of pectinolytic bacteria and the activity of pectinase in retting water. The optimum external retting conditions were as follows : pond water abundant in pectinolytic bacteria, water temperature 30℃-35℃, ratio of flax stem to water 1:20-25 and pH 7.0-7.5, Urea added into retting water by 2% of flax stem'mass. The different part, diameter and ripeness of flax had a different effect on flax retting. Therefore, it is necessary that the flax stems in same characeristic are selected together to ret in processing flax.(2)A bacteria strain with high activity of pectinase and xylanase was screened from flax stem. It was preliminarily identified and named Bacillus circulans Ae. Pectinase producing conditions by Bacillus circulans A& were studied in shake flask culture. The result showed that the optimum pectinase producing conditions were as follows: flax stem power 7 %, (NH4)2SO4 1 %, K2HPO4 0.15 %, pH 7.5, inoculum age 24 hours, inoculum amount 5 %, aeration 70 mL medium / 250 mL flask, agitation speed 200r/min. After cultivating for 20-24 hours, the highest pectinase activity was 7 800 U / mL.(3) Under the optimum growth condition, retting time of flax by Bacillus circulans A6 was 12 hours, which was shorter 84 hours than that of naturewater retting. Pectinase, xylanase, CMCase, proteinase and amylase were produced by Bacillus circulans Ae cultured with medium containing flax stem power as the sole source of Carbon. The culture filtrate of Bacillus circulans A6 at 25% (v/v) and ratios 1:15~20, were able to produce the flax fiber in 24 hours. The color, gloss and strength of fiber were better than that of nature water retting.