Screening Of Irpex Lacteus And Optimizing Of Its Enzyme Production And Degradation Of Straw

The objective of this study was to convert the crop straw resources to feed and increase the source of livestock feed. The Irpex lacteus which have the capacity of Lignin degradation was obtained.The enzyme production and the straw degradation conditions of Irpex lacteus were optimized. The results show that:1.The soil composition in5samplings from Yangzhou, Nanjing, Linyi, Weifang and Lianyungang were measured, and using the selective medium, coloration reaction of PDA-RB plate and PDA-Bavendamm plate identificatied the growth of lignin-degrading fungi and properties of lignin degradation enzyme in different soils. Finally, we choose advantage strain according to the growth characteristics of strains in different regional sampling points. The advantage strain was identified as the Irpex lacteus by the Chinese Academy of Sciences Institute of Microbiology. The results showed that lignin-degrading fungi density in soil of these five sampling points is greatly different, and it had positive correlation with the soil organic carbon content (r=0.84, P<0.01).Therefore, the lignin-degrading fungi density (5.67±0.58)105g-1in soil sampling point of Yangzhou was extremly higher than that of the other four sampling points (P<0.01), and the property of lignin-degrading fungi in producing enzyme was the supreme.2.The optimum temperature for Irpex lacteus to produce lignin peroxidase and manganese peroxidase was40℃. At this condition, the activity of lignin peroxidase and manganese peroxidase were more than31.61%and50.59%higher than20℃, respectively. The optimum temperature of producing laccase was30℃and it is different between producing different enzymes. Glucose as the best carbon source promoted Irpex lacteus to produce lignin degrading enzymes (P<0.05). Peptone was the best nitrogen source that promote Irpex lacteus production (P<0.01).6pieces of strain inoculation can promote strain to produce lignin peroxidase and manganese peroxidase.4pieces of strain inoculation can promote the generation of laccase. Orthogonal test showed that the activities of lignin peroxidase was higher at the condition which temperature was35℃, the contents of glucose and peptone was20g·L-1,4g·L-1, respectively, and4pieces of strain inoculation. The activities of manganese peroxidase and laccase were higher at the condition which temperature was35℃, the contents of glucose and peptone was20g·L-1,2g·L-1, respectively, and5pieces of strain inoculation.It was not consistent with the results of single factor experiment, proved that there was interactional relationship between various factors.3.It was advantage for degradation of NDF, ADF and ADL when wheat straw smashed. Compared with the untreated group, the degradation rate of NDF, ADF and ADL in cutting up treatment were higher42.42%and7.32%,78.12%and37.12%,90.95%and13.79%respectively. Under the condition of25℃, Irpex lacteus showed strong ability of lignin degradation, and the rate of ADL degradation was13.43%, higher than45℃.The degradation rate of NDF, ADF and ADL were higher when the inoculum concentration of Irpex lacteus was0.2g, but no significant effect on the degradation rate of lignin. For degradation of ADL in the wheat, the optimum contents of glucose was40g/L, and the rate was12.34%higher than20g/L group. The best peptone contents of Irpex lacteus to degradate lignin was8g/LIn conclusion, the strain Irpex lacteus in this study had the ability of degradating lignin. It was influenced by the culture conditions that the enzyme production ability of Irpex lacteus and the degradation to Various fibers in wheat straw.