Study On White Rot Fungi-Enzymes Degumming Of Hemp Bast

The hemp crop is one of the important economic crops in our country,and the degumming technology of its bark fiber is great significance for its higher value application.For the normal degumming techniques have some serious problems,such as low efficiency,degumming quality instability and wastewater pollution,which had long-term limited the development of bark fiber industry,and based on the characters that kenaf bark fiber gets higher level of lignin than other fiber and the lignin can be efficiently degraded by white rot fungi or laccase produced from white rot fungi,a new method that degums kenaf bark fiber with white rot fungi/laccase compound technology was studied.The main results are as following:(1)The optimized medium for laccase fermenting from combine fungi was studied.The optimal carbon source,nitrogen source and inducer were investigated.And then,by means of Plackett-Burman experiments,the steepest climbing experimental design and the center combination experiment design and response surface analysis,the optimum fermention formula for laccase was got finally:bran/glucose 40.98 g · L-1,Cu2+0.17 mmol · L-1,Tween-80 0.23%,soybean powder 3.0 g · L-1,pyrogallic acid 1.0 mmol· L-1,loaded volume 120 mL,inoculum dosage 8%,pH 4.0,and at last 48.23 U · mL-1 laccase activity could be achieved,which was 18.55 times of that of PS basal medium.The study on laccase properties shows,the laccase activity will be at highest level when it is at 40 ? and pH 5.5,and the laccase is stable under low temperature and weak acid.The laccase activity can be increased by low Cu2 + concentration,but inhibited by higher Cu2 +concentration.The study could laid a good material basis for enzyme degumming step.(2)Then the technology of white rot fungi-laccase compound degumming was studied.The effects of several pretreatment processes and degumming time on the degumming effect were investigated.The technical factors of enzyme degumming step were optimized.The result shows,when degumming the fiber with laccase liquor ratio 1:35 at 40 ? and pH 6.0 for 24 h,the residual pectin ratio would be down to 12.21%only and the breaking strength of the bundles reach to 4.93 cN·dtex-1.(3)It is proved clearly by microscope observation,FT-IR analysis,chemical component determination and strength test,while sequential degummed by white rot fungi and laccase,the kenaf bark fiber would has smooth surface,few pectin attachment and maintain high strength,it also means that the degumming effect is superior?In a word,the technology of degumming kenaf bark with white rot fungi and laccase will have many advantages,such as easy operation,non wastewater pollution and stability quality,which more superior than bacterium degumming and chemistry degumming ways.As a new kind of green degumming technique,it is expected to achieve significant application value and theory value.