Cellulase is an important enzyme product. It is a complex enzyme mainly composed of exo-β-glucanase, endo-β-glucanase and β-glucosidase. It also has high xylanase activity. Cellulase has huge market potential in the fields of feed, alcohol, textile and food. It will be the fourth largest industrial enzyme after glucoamylase, amylase and protease, and is a new growth point in the enzyme preparation industry.

There are many microorganisms that produce cellulase. So far, thousands of strains of cellulase-producing strains in 53 genera have been recorded at home and abroad, including bacteria, fungi and actinomycetes. At present, fungi are mainly used for cellulase production. 20% of the world's cellulase market comes from Trichoderma and Aspergillus. Among them, Trichoderma is recognized as one of the highest cellulase-producing species. , is the most commonly used strain in production.

Since Reese discovered Trichoderma from U.S. military uniforms during World War II, the industrial production of Trichoderma cellulase has attracted more and more attention, and T.ressei has become the most important enzyme in the world. Cellulase producing strains. Its advantages are that it has the characteristics of extensive cultivation and strong adaptability, and is suitable for solid culture and liquid submerged fermentation. Its enzyme system cellulase has high activity and can produce a large amount of extracellular protein. Its extracellular cellulose system consists of 60 It is composed of % to 80% exoglucanase, 20% to 36% endoglucanase and 1% β-glucanase. These enzymes work together to convert cellulose into glucose.

Mutation breeding is an effective method to improve the enzyme activity of strains. Taking the T.ressei Rut C-30 mutant strain as an example, it was obtained through 3-step mutagenesis (Qin Lingling et al., 2011) . First, strain M7 was obtained by screening for hydrolytic cellulase activity under metabolite inhibition conditions and performing ultraviolet mutagenesis; secondly, through chemical mutagenesis (nitrosoguanidine) and an enzyme whose process was similar to the former but more stringent. After live screening, strain NG14 was isolated from M7. In terms of extracellular protein and cellulase activity, NG14 increased several times compared with the parental strain and other available cellulase mutant strains (Eveleigh et al., 1979); finally, strain Rut C30 was obtained after ultraviolet mutagenesis of NG14 and screening for 2-deoxyglucose resistance (Kang et al., 2006; Wick et al., 1957). When Rut C30 was first isolated, the cellulase production could reach 15 FP units/(L·h), and it could produce about 20 mg/mL extracellular protein. Compared with its parent strain NG14, the production of extracellular protein was much higher. 2 times, reaching 2%, and the output in industrial fermenters exceeds 30g/L, reaching the enzyme output required by industry; compared with other Trichoderma strains, the exoglucanase produced by Rut C30 has the highest stability and is When cultured at pH 5.0 and 50°C for 30 days, only 28% of the enzymes were inactivated (Esterbauer H et al., 1991).

T.ressei mutant strains QM9414, MCG77, MCG80, Rut C30, CL-847, VTT-D and SVG are excellent strains for producing complete cellulase systems. When the above strains are cultured in an inorganic salt medium supplemented with cellulose (such as filter residue, cotton, microcrystalline cellulose, etc.) or treated lignocellulose (wood, straw), they can secrete cellulase (H. Esterbauera et al. al., 1991). Under laboratory shake flask fermentation culture conditions, the above strains can produce an average of 250 mg of cellulase protein for every 1 g of carbon source consumed, with a protein activity of 0.5 to 1.0 U/mg and a yield of 50 to 150 FP units/(L·h) , fed-batch continuous culture can increase enzyme concentration and production.

Research by Mach and Seiboth found that Trichoderma can also produce high concentrations of cellulase and hemicellulase using cellulose, xylan or other plant polymers or even industrial and agricultural by-products such as lactose as culture media phosphatase (Mach et al., 2003; Seiboth et al., 2007).

Trichoderma cellulase has recently been produced industrially. In addition to international brand companies Genencor and NovoNordisk, domestic companies such as Hunan Utel Enzyme Preparations have produced cellulases on a large scale.

There are two main modes of fermentation production of Trichoderma cellulase: solid-state fermentation and liquid fermentation.

The solid fermentation method uses corn and other crop straws as the main raw material. It has low investment, simple process and low product price. At present, most domestic cellulose manufacturers use this technology to produce cellulase (Qiyong Li et al., 2000). Chen Hongzhang and others from the Institute of Process Engineering, Chinese Academy of Sciences conducted research in the field of solid-state fermentation of cellulase and designed a 100m3 cellulase solid-state fermentation reactor and its supporting equipment, realizing large-scale production of cellulase using steam-exploded straw as raw material. Production, the maximum output reaches 210FPA/g dry koji. However, cellulase produced by solid fermentation method is difficult to extract and refine. At present, cellulase manufacturers in my country can only use the direct drying method to crush to obtain solid enzyme preparations or soak in water and press filter to obtain liquid enzyme preparations. The appearance of the products is rough and the quality is unstable. The fermentation level is unstable, the production efficiency is low, and it is easy to Contaminating bacteria.

The liquid fermentation production process is to crush corn straw to less than 20 mesh for sterilization treatment, and then send it to the fermentation kettle for fermentation. At the same time, cellulase strains are added. The fermentation time is about 70h and the temperature is lower than 60℃. The sterile air after sterilization is introduced from the bottom of the kettle for ventilation and stirring. The fermented material is filtered through plate and frame filter press, concentrated by ultrafiltration and spray dried to obtain cellulase products. Liquid submerged fermentation has become an important research and development direction at home and abroad due to its advantages of easy control of culture conditions, resistance to contamination by bacteria, and high production efficiency. Li Zhongxing et al. (1999) used T.koningii T215 as the bacterial strain and fermented cellulase in a 30t airlift reactor. The average CMC enzyme activity reached 78.3IU/mL.

Lu Zhaoxin of Nanjing Agricultural University and others studied the cellulase activity of Trichoderma cells immobilized with gauze covered with different polymers. Among them, the cellulase activity of Trichoderma immobilized by covering poly (HPMA) carrier was the highest. Up to 3.5IU/mL. Cellulase produced by immobilized Trichoderma cells was used to directly hydrolyze rice and wheat straw pretreated with radiation and low-concentration NaOH without purification and isolation. The glucose yield increased with the increase of irradiation dose and hydrolysis time. Electron radiation and 4 The glucose yield of rice straw treated with % NaOH reached 19%, while that of wheat straw reached 22%. It is believed that the immobilized Trichoderma cell enzyme solution can well hydrolyze the radiation-pretreated rice and wheat straw. The research result "Basic research on improving cellulase hydrolysis efficiency by combining radiation and biotechnology" won the second prize of the Science and Technology Progress Award of the Ministry of Agriculture in 1999.

Since cellulase is a multi-component complex, the substrate specificity of each component is different, and the composition and proportion of each component of cellulase from different sources are quite different. As a result, the determination method of cellulase activity is complex and inconsistent. There are many traditional cellulase activity determination methods, such as microcrystalline cellulase activity determination method, filter paper enzyme activity (FPA) determination method, salicinase activity determination method, dyed cellulose method, filter paper collapse method, cotton thread cutting method, carboxylase activity determination method, etc. Methylcellulose sodium salt (cmC-Na) enzyme activity determination method, marshmallow method, CMC viscosity reduction method, fluorescein determination plate method, etc. (Yin Juan et al., 2009). The use of new sensors to measure cellulase activity has been increasingly used in the production process. Biosensors are suitable for real-time and online determination of complex systems. They have the characteristics of rapid determination, simplicity and portability, high sensitivity, high specificity, and detection Samples can generally be used repeatedly, do not require the addition of other reagents, do not require pretreatment, and do not require sample clarity, etc., which show huge advantages in monitoring and control.