Study On Directional Conversion Of Bamboo Fiber To Ethanol By Compound Bacteria

Ethanol is a renewable and clean energy produced from biomass.The conversion of biomass to bioethanol plays a key role in reducing the world’s dependence on fossil fuels.In this study,bamboo and wood fibers are used as raw materials to optimize the flora combination,and their directional bioethanol conversion is systematically studied.The main results are as follows:(1)Bamboo fibers were used as raw materials and 800KGy dose of 60Co-y was used to The bamboo fibers were pretreated by X-ray irradiation.The characterization analysis was carried out by scanning electron microscope.It was found that the lignin and hemicellulose structure of bamboo fibers were broken and the cellulose was exposed.After measuring the components of lignocellulose before and after pretreatment,it was found that the cellulose content increased to 49.04%compared with the previous 40.52%,the lignin and hemicellulose content decreased,and the enzyme and substrate could be fully combined to improve the cellulase conversion efficiency.(2)Trichoderma reesei RuC-30 was mutated by UV.The optimal concentration of spore suspension is 104/ml,and the average number of single colonies on the plate is 193.The optimal UV mutation condition is that the vertical irradiation distance is 30cm and the irradiation time is 120s.Under this irradiation dose,the lethal rate of the strain is 87.60%and the forward mutation rate is 5.13%.The ratio(H/D)of the diameter(H)of the transparent hydrolysis circle and the diameter(d)of the colony formed by the strain on the Congo red screening medium is the basis of the preliminary screening,Then,a mutant strain 8.4-3 was screened based on the enzyme activity of the filter paper after the preliminarily screened strain was connected to the liquid fermentation medium.The enzyme activity of FPA filter paper was 128.24U/ml,which was 21.91%higher than that of the original strain.(3)The cellulolytic complex strains were constructed and cross inoculated with Aspergillus niger C112 and white rot fungus tramete versicolor on PDA respectively.It was found that there was no antagonistic reaction.It was found that the enzyme activity of filter paper was the highest when Aspergillus niger C112(V):Trichoderma reesei RutC-30(V)=1:9.The best inoculation method is:inoculate Trichoderma reesei RutC-30 first,and then connect Aspergillus niger C112 every 12 hours.Taking the pretreated bamboo and wood fiber as the substrate and adopting the optimized bacterial combination,the effects of five single factors such as carbon source content,pH,fermentation time,bacterial inoculation amount and nitrogen source content on the enzyme production of the composite bacterial system were explored.The results showed that the optimum conditions for enzyme production were carbon source content of 7%,pH=6,fermentation time of 4 days,inoculation amount of 4%and nitrogen source content of 8.5%.Through the response surface analysis,it was found that the interaction between carbon source content and fermentation time,nitrogen source content and fermentation time was significant.The enzyme production effect of the strain was 7.32%carbon source content,8.35%nitrogen source content and 3.74d fermentation time.Under this condition,the best simulation value of FPA enzyme activity was 277.15U/ml.(4)The yeast was used as the production strain and the sugar produced by the bamboo fiber hydrolyzed by the complex strain system was used as the carbon source for fermentation to convert ethanol.At the same time,the effects of five single factors,such as the amount of bacteria,pH,fermentation time,nitrogen source content and temperature,on the concentration of ethanol were studied.Through the single factor optimization experiment,the optimal fermentation conditions were obtained when the fermentation time was 96h,pH=7,the amount of bacteria was 8%,the temperature was 32℃,and the content of nitrogen source was 25%.Through the analysis of response surface test,it was found that the interaction between nitrogen source content and fermentation time,nitrogen source content and fermentation temperature was significant.When the fermentation time of Saccharomyces cerevisiae was 120h,the nitrogen source content was 24.91%,and the fermentation temperature was 32.50℃,the optimal simulation value of ethanol yield was 29.51mg/ml.