Microbial Fermentation Processes of Cellulase
China is a country with extremely scarce feed resources, with limited land and a large population. The contradiction between humans and livestock competing for food is very prominent. To maintain the sustainable development of China's feed industry and animal husbandry, it is necessary to solve the feed problem well, otherwise it will seriously restrict their development. Cellulose is a very abundant resource in nature, formed by the polymerization of 800-1200 glucose molecules.
Therefore, microbial fermentation can fully utilize agricultural and sideline product scraps, straw, and bran to produce Cellulase additives, which can improve the production performance of livestock and poultry, increase feed utilization rate. Cellulase also improves the nutritional value of feed, reduces feed costs, and increases economic benefits. It has broad development prospects, and in the future, research and development of Cellulase should be further strengthened.
Fermentation processes of Cellulase
There are two main production processes for Cellulase, namely solid fermentation and liquid fermentation, which are as follows:
Factors affecting Cellulase enzyme production and activity
There are many factors that affect Cellulase production and activity, in addition to bacterial species, including culture temperature pH, Moisture, substrate, cultivation time, etc. These factors are not isolated, but interconnected. Zhang Zhongliang et al. (1997) used uniform design Cl12 (1210) and green wood mold (T. ViriclePers. expr) as the strain to study the effects of five factors affecting Cellulase production on enzyme yield and activity. They believed that a substrate with a crude fiber content of 40%, an initial pH of 7.5, four times water addition, and 45 hours of cultivation at 26-31 ℃ could achieve a maximum Cellulase enzyme yield of 26mg/g and CMC enzyme activity of 20mg/g · h.
Wang Chenghua et al. (1997) also studied Cellulase enzyme production conditions of the mutant screened Trichoderma reesei 91-3. The results showed that the strain was cultured on a 7:3 mixture of straw powder and wheat bran, with the addition of 4% ammonium sulfate, 0.4% potassium dihydrogen phosphate, and 0.1% magnesium sulfate as the optimal medium. The suitable cultivation temperature was 28-32 ℃, the optimal temperature was 30 ℃, and the optimal inoculation amount was 4%. The fermentation peak was reached after 96 hours. Zhang Linghua et al. (1998) studied the optimal fermentation conditions for the high-yielding Cellulase producing strain Wu-932 obtained by mutagenesis using Aspergillus niger W-925 as the starting strain. The results showed that the optimal fermentation conditions were 1:2 wheat bran and rice straw powder as the culture medium, 5% inoculation amount, average length of rice straw pulverization of 3-5mm, initial pH of 4-5, temperature of 28-35 ℃, and fermentation time of 72 hours.
Control of contaminating bacteria
There is a common contamination of feed Cellulase, commonly known as "white haired bacteria". After pollution, enzyme activity decreases in mild cases and fermentation fails in severe cases. Therefore, studying the control of fermentation pollution is of great significance in regards to Cellulase production. Zhang Linghua et al. (1998) studied the colony characteristics, sources, growth and physiological features, as well as control methods of "white haired fungus", and found a tropical Candida J-931 that is in a symbiotic relationship with Trichoderma harzianum Wu-932 and in a competitive inhibitory relationship with "white haired fungus". Using this bacterium for mixed fermentation can effectively control the contamination of "white haired bacteria".
