Studies On Breeding Of Fungal Strain With High Yield Of Laccase And Degradation Mechanism Of Lignin In The Rape Straw By The Mutant

The white rot fungi Pleurotus ostreatus WY-01 was chose as the studying strain in this experiment,using the N + implantation bred a stable and high-yield of laccase with the mutant strain WY-02.Then,this experiment also studied the optimum solid medium and fermentation condition of the mutagenic stain WY-02 by orthogonal experimental design and using infrared spectrometry discussed the biodegradation mechanism of lignin in the rape straw by WY-02.The result of injecting N + in the Pleurotus ostreatus WY01was as following:when the implantation dose was 80×2.6×1014N+/cm2,the survival rate of spores increased 26%,and appeared the highest positive mutation.Therefore,80×2.6×1014N+/cm2 was decided the optimal N+ injecting dose.The activity of laccase of mutanted strain WY-02 was raised from4.17U/g to12.5U/g.Characteristics of enzymes production in WY-02 kept stable by 5 times subculture.By single and orthogonal test,the culture medium for the laccase production by the mutant strain WY-02 was studied.The optimum solid medium consisted of 10g/L glucose,0.2 g/L ammonium tartrate,0.015g/L CuSO4·5H2O,The study on optimal fermention conditions of the mutagenic stain WY-02 was indicated:the optimum fermentation temperature was 28℃,pH was 4.5 and seed volume was 3 germ bungs/15g,the optimum inductor was 1.0mmol/L ABTS.Fermented under optimum factors,the laccase of mutant strain WY-02 activity reached 15.3 U/g.FTIR spectrometer was used to analysis the change of lignin groups in rap straw which degraded by the mutant strain,in order to explore the degeneration mechanism of lignin in the rap straw by WY-02.As could be seen from the atlas,the 1635 cm-1indicated that C=O expansion vibration between lignin and the benzene ring was weaken obviously.The characteristics absorption peak of the benzene ring(1515cm-1) turned the peak into a small shoulder.The CH2 distortion vibration absorption peak (1460cm-1),which attributed in the lignin,became not obvious.The absorption peak (1324cm-1) was obvious reinforcement.The absorption peaks were respectively juliana lilac group's C-O( 1241cm-1) and guaiacyl group's O-H(1057cm-1),which vibrated weakly.From the above analysis we could see,the rap straw was degraded by the mutant strain,lignin had been significantly destroied.Not only the C=O link between lignin and aromatic rings,CH2 structure of the side chains and the lignin monomers(juliana lilac group and guaiacyl group)were partly degraded,but also aromatic rings of lignin was also destroied.This indicated that the structural carbohydrate of the rap straw was stepwise degraded by the mutant strain,the ring structure of lignocellulose was decomposed to the chain strucuture,thus the numbers of the methy and the hydroxy group were generally increased.This indicated that the white rot fungi mutagenesis strain had the unique superiority in the degradation of lignin,which was advantageous in the degeneration of the high lignification straw.