Strain Selection and Activity of Cellulase
Strain selection of Cellulase
Strain selection is a fundamental work in Cellulase production, and many experts at home and abroad have conducted extensive research. In order to produce high-quality Cellulaseroducts, Wang Jialin et al. (1996), based on absorbing domestic and foreign experience, successively introduced Trichoderma viride 10, Trichoderma viride Sn-91014, Aspergillus niger NT-15, and Aspergillus niger XX-15A. On this basis, physical and chemical mutagenesis methods such as ultraviolet radiation, specific electromagnetic wave radiation, linear accelerator, and nitrosoguanidine were used to obtain high-yield strains NT15-H, NT15-H1, XT-15H, and XT-15H1. The solid culture activity of Trichoderma NT-15H was tested by the Food Quality Supervision and Testing Center of the Ministry of Light Industry at Nanjing Station, and the filter paper activity was 3670u/g, Cellulase C1 enzyme activity was 24460u/g, and Cellulase Cx enzyme activity was 1800u/g, which has reached the international advanced level. This strain has stable performance in factory production. Zhang Linghua et al. (1998) used Trichoderma harzianum W-925, J-931, and obtained the Wu-932 Cellulase strain with high enzyme activity after composite mutagenesis with 2% diethyl sulfate and ultraviolet radiation (15W, 30cm, 2min). The Cellulase strain had a CMC saccharification power of 2975 and a filter paper enzyme activity of 531, which were 100% and 81% higher than the starting strain W-925, respectively. Wang Chengshu et al. (1997) from the Feed Additive Technology Service Center of the Ministry of Chemical Industry used the center's Trichoderma reesei A3 to undergo UV and nitrosoguanidine compound mutagenesis. The treated spores were inoculated onto a fiber bilayer plate, cultured at 30 ° C for 5-8 days, and left at 15 ° C for 7-10 days. Single colonies with larger transparent circle diameter and colony diameter were selected for solid-state fermentation in a triangular flask, and then screened to obtain the Trichoderma reesei 91-3 strain with high Cellulase activity.
The Cellulase strains are prone to degradation, and their enzyme production capacity significantly decreases after degradation. There may be three reasons for this:
① The strain screened by mutagenesis undergoes a revertant mutation.
② Natural negative mutation.
③ Long term low-temperature inclined storage of bacterial strains can lead to the growth of secondary hyphae on the conidia, and the vitality of the conidia formed by the secondary hyphae is weak, which may be the main reason for bacterial degradation. In order to avoid degradation of Cellulase strains, Zhang Linghua et al. (1998) reported using sand tubes to preserve the strains. The sand and soil that are about to be sieved and cleaned are mixed in a 3:2 ratio and packaged in test tubes. They are sterilized three times with a pressure of 1kg/cm2 for 30 minutes. The inclined bacterial strain to be preserved is prepared into a 1000ml spore suspension. 0.5ml is injected into each sand tube, shaken well, and stored in a vacuum dryer containing anhydrous CaCl2. After testing, the Cellulase enzyme activity remained basically unchanged within the 121 days tested; The time for Cellulase enzyme activity to decrease by 50% was extended from 60 days using conventional methods to 160 days, significantly slowing down the rate of bacterial degradation.
Factors affecting Cellulase activity
The optimal pH for Cellulase is generally between 4.5 and 6.5. Gluconolactone can effectively inhibit Cellulase, and heavy metal ions such as copper and mercury ions can also inhibit Cellulase. However, cysteine can eliminate their inhibitory effects and even further activate Cellulase. Plant tissues contain natural Cellulase inhibitors; It can protect plants from the decay caused by mold, and these inhibitors are phenolic compounds. If there is high oxidase activity in plant tissues, it can oxidize phenolic compounds into quinone compounds, which can inhibit Cellulase.
