Screening Of Crude Fiber Degrading Fungi From Distillers' Grains And The Preliminary Study On Degradation Conditions

Distillers'grains are rich in resources and are important renewable resources in China.The resource utilization of distillers'grains is of great significance for solving the problems of protein feed shortage and environmental pollution.Difficult-to-degrade crude fibres and lignin of distillers'grains seriously affect the distillers'grains into high quality protein feeds.Therefore,it is urgent to make a more effective biodegradation scheme for distillers'grains in order to promote the conversion of distillers'grains into high-quality protein feeds.For the safety of animals and humans,seven white rot fungi(Pleurotus floridanus,Stropharia rugosoannulata,Copyinds comatus,Lentinus edodes,Volvariella volvacea,Trametes cinnabarina,Ganoderma lucidum)were selected in this experiment.The best strains were determined by measuring the viability of their cellulase and lignin-degrading enzymes and their ability to degrade distillers'grains and husks.Then,the process of solid state fermentation degradation of distillers'grains and husks was optimized,and the effect of fungal hyphae on crude fiber detection of fermented feed was analyzed.It provides a theoretical basis for fermenting the distillers'grains to high quality protein feed.The results were as following.1.By discoloration experiment of PDA-guaiacol and PDA-aniline blue plate,Pleurotus floridanus,Volvariella volvacea,Trametes cinnabarina and Ganoderma lucidum were screened,which could produce high ligninolytic enzymes.Then,by experiment on CMC-Na-Congo red plate and microcrystalline cellulose Congo red plate,Pleurotus floridanus and Volvariella volvacea were screened,which could produce high cellulase.2.In the process of solid state fermentation of distiller's grains,comparing the ability to produce ligninolytic enzymes and cellulase and the ability to degrade crude fiber and lignin of distiller's grains in each strain.The results showed that:the ability of lignin-degrading enzyme produced from each strain was analyzed from highest to lowest,followed by Ganoderma lucidum,Trametes cinnabarina,Pleurotus floridanus,and Volvariella volvacea.The ability of cellulase produced from each strain was analyzed from highest to lowest,followed by Pleurotus floridanus,Volvariella volvacea,Trametes cinnabarina and Ganoderma lucidum.The best strain for degrading the lignin of distillers'grains is Ganoderma lucidum.The best strains for degrading the crude fiber of distillers'grains are Ganoderma lucidum and Pleurotus floridanus.In the solid-state fermentation of husks,comparing the degradation ability of lignin in the husk,Pleurotus floridanus is better than Volvariella volvacea;comparing the degradation ability of crude fiber in the husk,the two strains have no significant difference.Above all,Pleurotus floridanus is the most promising strain for degradation of distillers'grainsand rice husks.3.Degradation process of distillers'grains and husks by Pleurotus floridanus in solid state fermentation was optimized with single-factor experiments,center combination design experiments and response surface optimization.The optimized medium for degrading crude fiber in the husks by Pleurotus floridanus was:urea 1 g/L,KH₂PO₄ 2.15 g/L,Mg SO₄ 2.05g/L,ammonium tartrate 0.22 g/L,K₂HPO₄ 0.20 g/L,Ca Cl₂ 0.01 g/L,VB₁ 0.001 g/L;the optimized medium for degrading crude fiber in the distillers'grains by Pleurotus floridanus was:KH₂PO₄1.07g/L,Mg SO₄ 3.04 g/L,ammonium tartrate 0.22 g/L,K₂HPO₄0.20 g/L,Ca Cl₂ 0.01 g/L,V_B10.001 g/L?Compared with the initial Krik medium,the crude fiber degradation rate of Pleurotus floridanus increased from 10.34%to 17.08%after optimizing the culture medium,and the crude fiber degradation rate of distillers'grains was increased from 15.14%to 28.60%.4.Solid fermentation of wheat bran with Rhizopus oryzae,determine whether the total crude fiber content in the wheat bran fermentation medium was affected by the mycelium concentration of Rhizopus oryzae.The results showed that the content of Rhizopus oryzae mycelium in the solid-state fermentation process had a great influence on the determination of crude fiber.The crude fiber contents of Rhizopus oryzae(7d),Pleurotus floridanus(7d),Trichoderma harzianum(7d),and Candida utilis(2d)using GB standard method(GB/T6434-2006)were 33.36%,14.38%,17.14%,and 1.63%respectively?It can be seen that the crude fiber content in the solid-state fermentation medium measured by GB method contains the crude fiber of the fungal cell.