Introduction to Classification and Application of Cellulase

  • The optimum pH of cellulase is generally 4.5 to 6.5, which acts on cellulose and products derived from cellulose. Microbial cellulase is of great significance in converting insoluble cellulose into glucose and destroying cell walls in fruit and vegetable juice to improve the yield of juice.

     

    Classification of Cellulase

    1. Classified by composition and function

    According to the different catalytic reaction functions, cellulase can be divided into endoglucanase (1,4-β-D-glucan glucanohydrolase or endo-1,4-β-D-glucanase, EC3.2.1.4) and exo-glucanase (1,4-β-D-glucan cellobilhydrolase or exo-1,4-β-D-glucannase, EC 3.2.1.91). The endoglucanase randomly cuts the amorphous region inside the cellulose polysaccharide chain to produce oligosaccharides of different lengths and new chain ends. Exoglucanases act on the ends of these reducing and non-reducing cellulose polysaccharide chains to release glucose or cellobiose. β-glucosidase hydrolyzes cellobiose to produce two molecules of glucose. Fungal cellulase has high yield and high activity. Cellulase derived from fungi is mainly used in animal husbandry and feed work.

     

    1. According to the degradation mechanism

    The cellulase reaction is different from the general enzyme reaction. The main difference is that the cellulase is a multi-component enzyme system and the substrate structure is extremely complex. Due to the water insolubility of the substrate, the adsorption of cellulase replaces the ES complex process formed by the enzyme and the substrate. Cellulase first specifically adsorbs on the substrate cellulose, and then decomposes the cellulose into glucose under the synergistic action of several components.

     

    In 1950, Reese et al. proposed the C1-Cx hypothesis, which believed that different enzymes must work together to completely hydrolyze cellulose into glucose. The synergistic effect is generally considered to be that the C1 enzyme first attacks the amorphous area of cellulose to form a new free end required by Cx. Then CX enzyme cuts the cellobiose unit from the reducing or non-reducing end of the polysaccharide chain, and finally the cellobiose is hydrolyzed into two glucoses by β-glucosidase.

     

    Application of Cellulase

    Common livestock and poultry feeds such as grains, beans, wheat and processing by-products contain a lot of cellulose. Except for ruminant animals that can use part of it with rumen microbes, other animals such as pigs, chickens and other monogastric animals cannot use cellulose. In recent years, the use of fungal cellulase has become one of the important measures to improve livestock and poultry production performance and feed utilization.

     

    1. Inclusion in cattle diet

    A professor experimented with steers. 40g of cellulase per head was added to the diet every day and fed for 60 days. The results showed that the daily gain of the enzyme-added group was 892.78g and the control group was 746.8g. The difference was extremely significant. He used 30 Holstein cows for the test, and the test group added 50g of cellulase per head per day. The results showed that the total milk production of 15 cows in the experimental group was 2916kg in 68 days; while the total milk production of 15 cows in the control group was 2689kg in 68 days, the difference was significant.

     

    1. Inclusion in chicken diet

    Broiler diets are generally based on high fish meal, high corn, and high soybean meal. In order to reduce the usage of these conventional raw materials, cheap feed materials are widely used. Researchers increased the proportion of fiber-rich wheat bran in broiler diets, adding 0, 0.05%, and 0.1% cellulase preparations for experiments. The results showed that the daily weight gain of the 0.1% cellulase group increased by 4.31%, 4.54%, and 4.13% in the three growth stages of 1-2, 3-6, and 7-8 weeks compared with the control group. The material consumption ratio decreased by 1.56%, 4.50%, and 4.3% respectively.

     

    Researchers added 0.1%, 0.15%, and 0.5% cellulase to the diet of laying hens. The results showed that during the egg production period from January to October, the egg production rate increased by 0.53%, 1.25%, and 2.88%, respectively.

     

    1. Inclusion in pig diet

    Scientists added 0.6% and 1.2% cellulosic complex enzymes to the basal diet. As a result, the weight gain of growing and finishing pigs increased by 16.84% and 21.86%, respectively, compared with the control group.

     

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