The Study Of Screening Of Lignin Degrading Strains And Pretreatment Of Biomass By The Degrading Strain And Ionic Liquids

Renewable resources received considerable attention by people due to the extensive use of non-renewable resources such as petroleum,coal,and natural gas.As a renewable material for biorefinery,,the rich content of cellulose,hemicellulose,lignin contained in biomass that has great development potentail.Bioethanol prepared by using biomass that is rich in lignocellulose has become the focus of current research.Detailed expression can be considered as,above all,biomass is degraded into fermentable reducing sugar,and then bioethanol is produced by using this fermentable reducing sugar.However,the degradation of lignin has become an obstacle to the production of bioethanol.Now on,biological pretreatment methods,physical and chemical pretreatments,and ionic liquid pretreatment methods are considered to be the main pretreatment methods.Therefore,screening of lignin-degrading strains becomes an effective way to reduce the waste of biomass and this method shows the feature of environmental protection,cheap and effective.In this paper,soil samples are collected from Wenshan County in Yunnan Province,Bengbu City in Anhui Province and Keshan County in Harbin City.Moreover,it should be noted that samples were covered with dead wood and straw before they are taken.After the process of enrichment culturing using liquid medium,dilution coating,dash separation and identification culturing by using PDA-guaiacol,4 strains with a red-brown oxidation ringare are screened out.Rescreening method is implemented using liquid fermentation to obtain the strain named KS-2.Finally,KS-2 was identified as Trametes according to morphological identification and molecular biological identification.Laccase activity of 107 U/L about KS-2 was shown by the Determination of enzyme activity results.Therefore,the KS-2 strain was used as the starting strain to optimize production conditions of this enzyme.Then,the effects of carbon source,nitrogen source,Cu²⁺concentration,initial pH value,and culture temperature on the laccase activity of strain KS-2 are investigated due to single-factor experiments.The results show a best enzyme activity of 631 U/L,which is based on the cultivated condition by using a 1:1 ratio of glucose and corn stover as a carbon source,peptone as a nitrogen source,an initial pH of the medium at pH 5.5,28°C cultured temperature and 10 day training time.The enzyme activity in this cultivated condition is 5.9 times higher than that before the optimization of culture conditions.Under the best enzyme production conditions,degradation of corn straw powder by strains are investigated in different days.Raw corn stalk powder shows the feature of smooth surface without voids,but the stalk powder that is degraded shows the rough surface with cracks and voids.According to the Biomass composition determination method of United States Energy Agency,40.1%of degradation rate is shown after 5 days of degradation.Similarly,10 days of degradation shows the 53.3%of degradation rate,15 days of degradation presents the 65.4%of degradation rate.In this study,three ionic liquids including[Hpy]Cl,[Hnmp]Cl and[Hmim]Cl are synthesized.The mixture of poplar flour and bamboo flour are heated at 90°C and 100°C respectively for 30 min in an oil bath by using these synthesized ionic liquids.After processing,the yield of lignin and cellulose-rich material is detected.The Lignin or cellulose-rich material that is treated by using ionic liquid are analyzed by the SEM,Crystal analysis,FT-IR and 2D ¹H-¹³C HSQC.The higher lignin yields are demonstrated after the pretreatment of poplar powder by using[Hpy]Cl,and compared with the original lignin in poplar powder,61.0%of yield is shown.However,51.7%of yield of bamboo flour is shown under the same conditions.More specifically,improving the pretreatment temperature could increase the lignin yield significantly.Structure type of S-G-H of Lignin pretreated by ionic liquid is determined by the FT-IR and HSQC.Two pretreatment methods in this study can be used to remove lignin efficiency in biomass for obtaining the cellulose-rich material that produce reducing suger.Lignin-degrading strain has a high laccase activity,lignin in straw could be effectively degraded,to obtained the straw cellulose residue.Ionic liquid pretreatment method could not only obtain the cellulose residue but also efficiently separate the lignin.Moreover,it is applied to produce lignin chimeric agents and adhesives in industry.