平菇(Pleurotus ostreatus)对稻草中木质素的生物降解及降解产物分析

Biodegradation of Lignin by Pleurotus ostreatus in the Straw and Analysis of Degradation Outcome

变色圈试验证明平菇可以选择性优先降解稻草中的木质素,培养15d后,平菇对稻草中的木质素降解率为17.86%,对综纤维素降解率为2.44%,选择性指数为9.79。生料栽培平菇后,稻草中的木质素被降解50.24%。用气—质色谱(GC/MS)和红外光谱(IR)对木质素降解产物分析结果表明,平菇对稻草中木质素的降解效果十分明显,降解产物中检测出了大量含有苯环的小分子,证明木质素聚合体的降解首先发生在单体的侧链及单体间的连键上,发生Cα-Cβ、β-O-4等断裂,形成了单体。在进一步的降解过程中,平菇表现了其自身特有的降解机制,取代苯环单体上的甲氧基为甲基,而后发生苯环的开裂,这与报道的白腐菌降解过程有所不同。红外光谱分析中,平菇对木质素的降解明显,降解产物中含有很多木质素单体所特有的基团,如紫丁香基、愈创木基等,说明木质素的降解首先发生的是侧链的氧化反应。

The experiment of discolor zone indicates that Pleurotus ostreatus can selectively degrade lignin, and the rate of lignin degradation is 17,86% after 15 days＇ culture, the cellulose degradation rate is 2.44% and the Select Factor （SF） is 9.79. The rate of lignin degradation in the non-autoclaved straw which cultivated Pleurotus ostreatus is 50.24 %. The result of the analysis to the degradation outcome of lignin by GC/MS and IR shows that the degradation effect by Pleurotus ostreatus is very effective. In the GC/MS analysis, lots of compounds containing benzene ring were detected. It proves that lignin polymer was degraded when Pleurotus ostreatus was cultured. The breakage first occurred on the side chain and the bond between monomers, such as Cα-Cβ, β-O-4 etc., and formed the monomers. Then Pleurotus osreatus exhibited its special degradation mechanism, methoxy was displaced by methyl, then the ringopening reaction happened. It is different from the reported about the degradation mechanism of white-rot fungi. In IR analysis, the result is the same as that of GC/MS. In the degradation outcome by Pleurotus ostreatus there are some special groups such as guaiacyl and syringyl. The result proves that lignin is degraded by Pleurotus ostreatus, and the first oxidation is on the side chain of monomer.