Effect of chitosan on the diffusion rate of the mycelium
The effect of different concentrations of chitosan on the diffusion rate of the mycelium is given in Table 1. There was an obvious effect on the Lentinula edodes mycelium growth of the different chitosan solutions. When the solution concentrations were 0.1 mg/ml and 0.5 mg/ml, the mycelium grew fast and dense, which was significantly different from the control group. Among them, it performed better at the 0.1 mg/ml concentrations. However, the mycelium growth rate of the two groups was not significantly different. When the solution concentrations were 0.017 mg/ml, 0.007 mg/ml, and 0.005 mg/ml, the mycelium growth rate was not significantly different from the control group.
Table 1
Effect of different concentrations of chitosan on mycelium diffusion rate of the Lentinula edodes on the substratum(mm/d)
Chitosan concentration (mg/ml) | Average growth rate of mycelium(mm/d) | Significant Difference | Mycelium growth |
α = 0.05 | α = 0.01 |
Control | 3.005 | c | B | + |
0.005 | 4.018 | bc | AB | + |
0.007 | 4.385 | bc | AB | ++ |
0.01 | 4.678 | b | AB | ++ |
0.017 | 4.683 | bc | AB | + |
0.05 | 4.703 | b | AB | +++ |
0.1 | 6.360 | a | A | ++++ |
0.5 | 6.265 | ab | A | ++++ |
Notations: “++++” means strong growth of mycelium;“+++”general growth;“++”and “+” poor growth. |
Chitosan is a natural cationic polymer that could stimulate the development of the roots and stems and enhance the resistance of the plant. Meanwhile, it can also improve the quality and quantity of the plants (Olaiya 2010).The mechanism of the chitosan to stimulate the Lentinula edodes mycelium growth could be the stimulation of the mycelium cell to divide and grow. It may also promote the physiological activity of Lentinula edodes mycelium cells, thereby activating and improving the related enzyme activity. Afterward, enhance the absorption and utilization of the nutrients, resulting in the acceleration of the mycelium growth.
Effect of chitosan on mycelial CMCase activity
The effect of chitosan supplementation on CMCase activity of mycelial cells is shown in Fig. 1.The mycelial CMC enzyme activity of all groups treated with chitosan was higher than the control group when the chitosan concentration was 0.1 mg/ml, and its mycelial CMCase enzyme activity was the highest; Compared with the control group, when the chitosan concentration was 0.05 mg/ml, the mycelial CMCase enzyme activity was increased in the first 12 days, and the mycelial enzyme activity of CMCase was obviously decreased from the 18th day. When the chitosan concentrations were 0.017 mg/ml, 0.01 mg/ml, and 0.007 mg/ml, the mycelial CMCase enzyme activity was the same as that of the control group. The trend of the mycelial CMCase enzyme activity was different with time, its activity increased from day-0 to day-18, and then decreased, there was a second activity peak for 0.1 mg/ml, 0.5 mg/ml, 0.007 mg/mL and the control, but it was smaller than the first peak, and then the mycelial CMCase enzyme activity decreased.
The CMCase is an important cellulose enzyme, which could hydrolyze and generate certain glucose with the help of the CMCase, promoting the Lentinula edodes mycelium cell growth. Moreover, the mycelial growth rate reached its maximum from the 12th to the 18th day. The interesting thing was that the mycelium entered the physiological maturity period from the twenty-fourth to thirty-sixth day, and the CMCase enzyme activity was decreased. The reason was most probably because the CMCase enzyme was an inducible enzyme, as the exocellular enzyme of the mycelium cell, which was secreted little during the early growth period of the microorganism. Research also discovered the enzymatic secretion increased following the growth of the mycelium and was related to the age of mycelium.
Effect of chitosan on the mycelium amylase activity
The effect of chitosan solutions on the mycelium Amy activity is represented in Fig. 2. When the chitosan concentration was 0.1 mg/ml the Amy activity of Lentinula edodes mycelium was the highest, which was significantly higher than the control group.
At the chitosan concentration of 0.05 mg/ml, the Amy activity was significantly higher than that of the control after 12 days of continuous culture. Surprisingly, the activity of Amy was reversed and decreased as in the control group after 18 days., and then it stayed normal. Overall, the amylase activity showed an earlier increase and later decrease trend, and the amylase activity reached a maximum on the 12th day.
The starch in the medium can be hydrolyzed into glucose under the effect of the Amy, and the glucose is an important carbon source for the Lentinula edode growth. Amy of Lentinula edode exocellular had high catalytic activity, but its activity was reduced and then always kept at low level when the mycelium came into the mature periods. The starch was the rapid carbon source that was used by the Lentinula edode in the early growth period, and the amylase activity decreased with the growth of the mycelium, corelating to the mycelium growth rate. The chitosan could be a growth regulator for the Lentinula edode, playing a role in improving the Amy activity, and providing the carbon sources and energy for the mycelium growth.
Effect of chitosan on the POD activity of mycelium
The effect on the mycelium POD enzyme activity in the cultivation of different chitosan is shown in Fig. 3. The mycelium POD enzyme activity of the control group changed little. In the first 12 days, the activity of each concentration had changed to some degree. The mycelium POD enzyme activity of other groups was higher than that of the control group until 18 days of cultivation, but at other times the activity was almost lower than that of the control. POD is a lignin enzyme, that could accelerate the degradation and use of the lignin aromatic compounds, lignin, cellulose, and hemicellulose are the main components of the plant skeleton (Sakurai 1998). Also, the enzymatic activity of POD reached its highest peak in the mycelium’s rapid growth periods (from 12th to 20th day), and then the mycelium entered the physiology maturity periods (from 24th to 36th day). When the chitosan concentration was 0.1 mg/ml, the POD enzyme activity was significantly higher than the control group, which showed not only the mycelium of the Lentinula edode mycelium POD enzyme activity, but also the degradation of the lignin. At the same time, the degradation of the cellulose was increased and the mycelium grew better after being treated with chitosan.
Effect of chitosan on the mycelium peroxidase isozyme
The effect on the mycelium peroxidase isozyme in the cultivation of the different chitosan is shown in Fig. 4. The Lentinula edodes peroxidase isozyme has 3 enzyme belts. The strength of the first and second belt was different when compared to the control. The third belt of all the groups was strengthened compared to the control when the chitosan concentration was 0.5 mg/ml and 0.1 mg/ml, the enzyme belt was the widest, colored the fastest and dyed the deepest, and at this concentration, there was the most obvious enhancement effect. When the chitosan concentrations were 0.017 mg/ml and 0.05 mg/ml, the enzyme belt was wider, colored faster, and dyed deeper, and the enhancement effect was better, but the effect of enhancement was not obvious.