Screening And Identification Of Lignocellulose Degrading Bacteria And Degradation Products Research

The complex structure of lignin obstructs the utilization of cellulose and hemicellulose.Biodegradation is safety and efficiency to environmental.In this research,we screened bacteria which had lignocellulose degradation ability from different separation sources,and obtained functional strains by analyzing their degradation characteristics and degradation mechanism.Finally,applied them to the hay and explored its effect on the quality of hay.This research consists of four experiments.In the first experiment,12 target strains were obtained through preliminary screening.Congo red and aniline blue were added to the media as respectively.After that,6 target strains were carried out while the media have hydrolysis circle,the different carbon sources utilization was tested at the same time.This study identified 6 strains of bacteria with lignin degradation ability,they are Bacillus aryabhattai,Acinetobacter johnsonii,Acinetobacter lwoffii,Micrococcus yunnanensis,Duganella zoogloeoides and Sphingobium yanoikuyae.Experiment 2 completed the determination of the efficiency to degrade alkaline lignin,and then measured lignin peroxidase(Lip)activity,manganese oxide enzyme(Mnp)activity,laccase activity(Lac)and cellulase activity.Subsequently,the response of lignin peroxidase and manganese oxide enzyme activities to different temperatures was researched.The degradation rate of alkaline lignin degradation was 38.8%~53.5% by 6 strains respectively.The highest enzyme activity of A.johnsonii and A.lwoffii Lipase activity after 3 days fermentation was 6594 U·L-1 and 7151 U·L-1,respectively.The activity of Mnp was the highest after D.zoogloeoides and M.yunnanensis fermentation for 48 h,which were 13529 U·L-1 and 12533 U·L-1.The optimum temperature for the degradation of lignin by the six functional strains was similar to the ambient temperature.The Lip and Mnp enzyme activities were optimum at 40°C of two Acinetobacters.The third experiment mainly studied the degradation products of alkaline lignin and the degradation mechanism.Firstly,the products in the fermentation broth were analyzed by gas chromatography-mass spectrometry through three different polar solvents,and the possible degradation pathways were analyzed.The degradation products of the six strains were similar,and all of them were metabolized to produce palmitic acid,octadecanoic acid and valeric acid lactone,while 2,2'-dimethylbiphenyl,2,2',5,5'-Aromatic organic compounds such as tetramethylbiphenyl,acetosyringone,and dibutyl phthalate are degraded and utilized.Six strains may utilize aromatic organic compounds through the biphenyl metabolic pathway and the DBP aerobic metabolic pathway.In the fourth experiment,the laboratory hay hydraulic machine was designed,and the laboratory hay was made subsequently.The degraded bacterial suspension was inoculated for 30 days,and nutrients content of the hay was measured by NIRS and the forage quality was evaluated.The results showed that the alfalfa hay quality improved after inoculation.A.lwoffii was the best one which promoted the nutrients and quality significantly,while oat hay had not been improved with inoculants.In this research,six strains of lignin-degrading bacteria were isolated from different environment.These strains have obvious effects on the quality improvement in alfalfa hay.And A.lwoffii was the striking strain.All the strains could be used in lignin energy,especially as a guidance to promote the quality of forage.