| With the exhaustion of fossil energy and the aggravation of global energy crisis,the development and utilization of renewable resources are attracting more and more attention.As the most important energy sources,biomass energy plays an irreplaceable role in replacing traditional fossil fuels and solving energy crisis.Sweet sorghum can be used as a new"high-energy crop",because of its strong growth capacity and high sugar content,which plays an important role in guaranteeing national energy and food security.In particular,sweet sorghum straw,chosen as an important biomass resource,has been continuously developed and utilized,and its economic and ecological benefits have become increasingly prominent.At present,the most promising utilization way of biomass energy is the biological method,which mainly utilize cellulase to decompose lignocellulosic polysaccharides into fermentable sugars,and then produces biofuels such as bioethanol and butanol and other high value-added chemical products.However,there is a"biomass recalcitrance"in the degradation and transformation process of biomass materials,resulting in high cost,low efficiency and great difficulty in enzymatic hydrolysis of lignocellulose.In order to enhance enzymatic hydrolysis yield,two solutions are proposed:one is to develop cellulase with high degradation ability;Another is to adopt various pretreatment methods to pretreat biomass material to improve the accessibility of enzyme to substrate and thus improving the hydrolysis yield.This paper mainly studied the hydrolysis effect on sweet sorghum straw of five groups self-made cellulase,and optimized a cellulase with high degradation ability on sweet sorghum straw.In order to improve the enzymatic hydrolysis yield of sweet sorghum straw,the components of cellulase produced by aspergillus MS160.53 were analyzed,and the cellulase BGL proportional adjustment model was established to guide the adjustment of cellulase lacking in BGL.Meanwhile,Sweet sorghum straw was pretreated using heavy ion beam irradiation(HIBI)to destroy the recalcitrance of biomass and improve the enzymatic accessibility and the hydrolysis degree for substrate.The mechanism of heavy ion pretreatment of lignocellulose was studied by means of XRD,FTIR and AFM.The main research results are as follows:1.Optimization of cellulase for high-efficiency degradation on sweet sorghum strawThe cellulase that efficiently degrade sweet sorghum straw was optimized,and its hydrolysis yield reached 12.16%for sweet sorghum straw.Its production strain can be chosen as the optimal strain for cellulase production to conversion sweet sorghum straw into biofuel,which will greatly promote the application of biomass resources of sweet sorghum straw as bioenergy.2.Study on cellulase compounding to improve the decomposition capacity on sweet sorghum strawThe BGL proportion adjustment model y=1183.9x+3.4255 was established and its R~2=0.9878.After compounding,the enzymatic hydrolysis yield of sweet sorghum straw was 19.26%,which was 15.2%higher than that of the non-compounding enzyme(P<0.05).The adjustment of BGL ratio in cellulase provides a new perspective for the efficient decomposition on lignocellulose into fermentable and biofuels.3.Study on the improvement of enzymatic hydrolysis yield of sweet sorghum straw using heavy ion beam irradiation pretreatmentThe enzymatic hydrolysis yield of sweet sorghum straw pretreated by 600 Gy of heavy ion beam irradiation(HIBI)for 36 h was reached 34.43%,it is an increase of46.7%compared with the control.The study of mechanism showed that the change of ultrastructure on the surface of sweet sorghum straw was the main factor to improve the hydrolysis yield.In addition,HIBI pretreatment also resulted in different degrees of damage on crystalline structure of sweet sorghum straw and the gradual transformation cellulose I_αinto I_βas a result of the fracture of hydrogen-bonding.This indicated that heavy ion irradiation could be employed as a novel pretreatment technology to improve the enzymatic hydrolysis yield of lignocellulose,which filled the gap in the field of biomass material irradiation pretreatment. |
