Study On Pretreatment Of Rice Straw With Biological Enzyme And Its Application

The energy shortage and environmental pollution caused by the rapid development of human society have made people realize the importance of using renewable biomass resources.As the main source of biomass resources,lignocellulose shows good environmental and economic advantages in terms of conversion into bio-based materials and biofuels.my country has very rich biomass resources and is the world’s largest producer of rice and wheat.However,a large amount of waste crop straws are not effectively used every year.The internal structure of lignocellulose such as crop straws is tight and regular,and most of the cellulose is embedded in it,making it difficult for lignocellulose to be reasonably utilized as a resource.Therefore,the key bottleneck of lignocellulose resource utilization is to destroy its internal structure and release cellulose.There are two most widely used methods of cellulose: using the extracted cellulose to prepare cellulose-based materials or enzymatically hydrolyzing cellulose to obtain fermentable sugars to prepare bioethanol.The biological enzyme pretreatment process has the advantages of high efficiency and environmental protection,and has developed rapidly at home and abroad,showing a good application prospect.However,at present,the pretreatment of lignocellulose with biological enzymes is mainly used for degumming in the textile industry,and most of them are processed by a single biological enzyme.There is a problem of low processing efficiency,which needs to be further improved.Therefore,in response to the above shortcomings,this paper develops a new type of biological enzyme system pretreatment technology from the perspective of improving the added value of cellulose resource utilization and optimizing the biological enzyme pretreatment process.The technology was applied to the pretreatment of rice straw,and its treatment effect and mechanism of action were studied,and it was applied to the preparation of cellulose-based materials and bioethanol.The following research results and conclusions were mainly obtained:(1)The effects of enzyme activity ratio,pretreatment temperature,and pretreatment time of different biological enzyme systems on rice straw components were investigated.The results showed that the removal rate of lignin reached more than 85%,and the cellulose content increased by 53.7%,in the pretreatment condition of the bio-enzyme system,of which enzyme activity ratio,treatment temperature and time are 30:20:2,45 ℃ and 24 h respectively.Meanwhile,the biological enzyme system also has a good pretreatment effect on lignocellulosic raw materials such as corn cob and bagasse.The pretreatment method can effectively remove non-cellulose components in lignocellulose,and provide a basis for realizing high-value utilization of lignocellulose.(2)The mechanism of the biological enzyme system on the pretreatment of rice straw was systematically studied.SEM,BET and TG results show that the P/X/L biological enzyme system can remove a large amount of hemicellulose,lignin and other components in the straw fiber,destroying the dense structure of the straw fiber,Increase the specific surface area,pores and pore volume.The results of FT-IR and XRD show that the pretreatment method can break the bonds between the components of the rice straw,remove non-cellulose components while retaining its original I type crystal structure,and has good mechanical properties for the preparation.And mechanical properties of cellulose-based materials offer the possibility.(3)After the rice straw is pretreated by the biological enzyme system,high-intensity ultrasound and freeze-drying methods are used to prepare nano-cellulose aerogel materials with good thermal insulation properties.The effects of the ultrasonic parameters of high-intensity ultrasound and the modifier methyltrimethylsiloxane(MTMS)on the thermal insulation performance of aerogel materials were investigated.The ultrasonic power was 550 W,the ultrasonic time was20 min,and the modifier was added.When the ratio is 1:2(nanocellulose suspension:MTMS),the thermal conductivity of the obtained aerogel material is 0.03828W/Mk.(4)The effects of different biological enzyme system enzyme activity ratios,pretreatment temperature and time on the enzymatic hydrolysis and saccharification of rice straw were investigated.After the rice straw is treated at a temperature of 45℃and a pretreatment time of 24 h,in the condition of the enzyme activity ratio of30:20:2,the yields of reducing sugar and glucose reached the highest,897mg/g and652mg/g respectively,which were consistent with the compositional changes of straw.