Detoxification Of Ferulic Acid In Alkali-pretreated Lignocelluloses Hydrolysates

As conventional energy is decreasing and environment pollution is aggravating,the production of bioethanol by lignocellulosic material was paid much attention nowadays.However,various kinds of inhibitors,including ferulic acid,acetic acid and furfural,will be produced in cellulose hydrolysate after pretreatment.These inhibitors could restrain the subsequent hydrolysis and fermentation process for bioethanol production.To solve these problems,ferulic acid was selected as the main objective in this article to purposefully detoxify this main inhibitor existed in the hydrolysates.Meanwhile,the mechanism of detoxification was investigated to increase the degradation rate of lignocellulose,thus providing scientific basis for bioethanol production.An effective ferulic acid degrading bacteria,named as HHQ-1 and identified as Stenotrophomonas sp.,was isolated from polluted soil by concentration gradient screening.By orthogonal experiments,the optimum growing condition for HHQ-1 was investigated,which was adding 7%HHQ-1 inoculation?the initial concentration of ferulic acid was 1250mg/L?at 30? when pH value was 9.Meanwhile,the optimum degrading condition for HHQ-1 was investigated,which was adding 7%HHQ-1 inoculation?the initial concentration of ferulic acid was 1250mg/L?at 30?when pH value was 8.HHQ-1 was added in-situ into lignocellulose degrading process in the present study,where both cellulose degrading microbe and ferulic acid degrading bacteria worked together.Thus,the consortia degrading system was built.It was shown that the production of reducing sugars could increase 7.84%in the consortia degrading system compare to the single degrading system.OD₅₅₀ and conductivity in the two different degrading systems were analyzed.It was indicated that the optimal grow condition for the consortia degrading system was 25-30?,pH 6.5 when the inoculum ratio of Trichoderma reesei to HHQ-1 was one to three.Compared to the single degrading system,the cell quantity was increased and the breakage rate was decreased in the consortia degrading system.The optimum condition for cellulases hydrolysis in the consortia degrading system was investigated by orthogonal experiments,which was adding 3 mL Trichoderma reesei at 30? when pH value was 8.The composition of cellulases was studied both in consortia degrading system and single degrading system.It was indicated that the adding of HHQ-1 to the single degrading system could degrade ferulic acid inhibitor,thus increasing the stability of cellulases and enhancing the proportion of ?-glucosidase in the consortia degrading system.Scanning Electron Microscope?SEM?,X-ray Diffraction?XRD?and Fourier Transform Infrared Spectrometer?FTIR?were used to observe the morphological changes of rice straw biomass.It was indicated that in-situ detoxification could severely destroy basic tissue of rice straw,dramatically decrease crystallinity index of crystalline region and effectively degrade refractory-degraded lignin parts of lignocellulose.Compared to the single degrading system,the consortia degrading system could detoxify the main inhibitors which existed in pretreated rice straw hydrolysates,thus increasing the bioethanol yield and reducing the cost of bioethanol production.The consortia degrading system was supposed to be an effective choice for bioethanol production in large scale.