Team:Shanghai YGQ/Improve
Improve
Effect of LuxR on wood vinegar bacillus
Fermentation performance of strain under oscillation condition
Develop original strains by oscillation G.x and expression strains Gx - pMV24 - IuxR, comparison of two strains of bacteria fermentation performance, the results are shown in figure 3 to 7, with the increase of incubation time, compared with the original strain G.x, and the expression of strain Gx - pMV24 - luxR bacteria growth weakened obviously, growth rate is relatively slow, and to 72 h, both glucose is depleted from the culture medium, from this moment beginning, strains of bacteria volume between gap is also slightly bigger, and 120 h, the bacteria volume compared with the original strain, was reduced by 16.05%. Under the condition of oscillation, the fermentation performance and total acid content of each strain showed no significant difference, as shown in figure 3-7(c).
For glucose utilization, both strains used glucose as the main carbon source for the growth and metabolism of bacteria in the first 72h. In the first 24h, there was no significant difference in glucose consumption between the two strains. However, from 36h to 60h, the glucose consumption of the overexpressed strains was relatively more than that of the original strains. Although overexpression of strains of glucose using speed, bacteria volume less, but its in 72 h before the production of gluconate, most in the 60 s h, reach maximum glucose acid content is 16.50 g/L, the original strain increased by 12.11%. Zhong 06 with fake steady-state analysis, research g. xylimus cells with glucose as the substrate metabolism of flow distribution, the results showed that 40% of the carbon source to glucose acid, that is to say, in the first 72 h, compared with the original strain, the flow of overexpression of metabolic flow strain more glucose acid.
After static culture, the difference of cellulose yield and fermentation performance between the two strains were compared. The results showed that the cellulose yield of the overexpressed strain gx-pmv24 IhuxR was significantly higher than that of the original strain from the beginning of fermentation. By the time glucose was exhausted on the 16th day, the cellulose yield of the overexpressed strain reached 5.012 g/L, 36.45% higher than that of the original strain, as shown in figure 3-8(a). As for the utilization of glucose, as shown in FIG. 3-8(b), the glucose consumption rate of the overexpressed strain g.x-pmv24-luxr was slow due to dissolved oxygen and other factors. The sugar utilization rate of the overexpressed strain g.x-pmv24-luxr was significantly higher than that of the original strain from the beginning of fermentation. As shown in figure 3-8 (c), and the oscillation of fermentation, quiet place in the process of training both a significant difference between the total acid content, from 8 d, expression strains pH at a higher than the original strains, which means the total acid content in the fermented liquid to lower than the original strains, and 16 d at the end of the fermentation, reached the highest pH is 4.48, is 8.75% higher than the original strains, but gluconate is different, the two strains of bacteria were accumulated in the first 4 d glucose acid, achieves maximum 4 d, But express strain levels low of 7.69 g/L, 9.7% lower than the original strains. The original strains glucose acid content until 12 d has remained steady at around 8.50 g/L, starting from 12 d glucose acid content is reduced, and 16 d 5.7 g/L, and the expression of strain in 4 d - 8 d, glucose acid content changed little, keep at around 7.30 g/L, 8 d began to cut down the content of glucose acid, and 16 d to a minimum of about 4.36 g/L, 23.68% lower than original strain, as shown in figure 3-8 (d). Above all, let stand conditions, The overexpression strain increased the glucose consumption rate, produced less gluconic acid, and significantly increased the cellulose production. That is to say, the overexpression of luxR improved the utilization rate of gluconic acid.
Oscillation and static buy two ways compared through strains with the original strain fermentation performance difference, the result showed that shaking culture conditions, the original strains, overexpression of strain G.x pMV24 - huxR bacteria growth rate slows, glucose utilization rate is accelerated, produced more gluconate, and late fermentation glucose depletion, the utilization of glucose acid significantly enhanced. Under the static condition, the overexpressed strain increased the glucose consumption rate, produced less gluconic acid, and significantly increased the cellulose production. In other words, luxR overexpression improved glucose utilization.