| The paper is to find out the effects of aeration, agitation, dissolved oxygen concentration (DO), pH on batch microbial transglutaminase (MTG) fermentation in 10L bioreactor. An initial study has been made on glucose feeding in 10L bioreactor and magnifying in 50L bioreactor before the presentation of a model of batch MTG fermentation which is made up of three mathematical equations. The following are the conclusions drawn from the experiments:1. In flask a variety of mediums are used to study the kinetics of batch Microbial transglutaminase (MTG) fermentation. The results show that batch MTG fermentation is a mixture type (Luedeking-Piret model) which is a mixture of growth associated and non- associated terms.2. The agitation and aeration in 10L bioreactor is also researched in this paper. 350rpm agitation is good for cell growth and MTG synthesis. Likewise, l.Ovvm aeration is of the same positive effect on cell growth and MTG synthesis. At last, we optimized the agitation and aeration in 10L bioreactor under the following conditions:agitation: 0h-8h, 250rpm; 8h-32h, 350rpm; after 32h, 250rpm aeration: 0h-8h,0.6vvm; 8h-32h,1.0vvm; after 32h,0.7vvmThe results show that MTG reaches 4.36(u.ml-1) at the 47th hour and yield coefficientfor cells on carbon substrates (Yx/s) is 1.545(g.g-1)3. We also studied the effects of dissolved oxygen concentration (DO) on batch MTG fermentation. High DO (30%) is good for cells growth and MTG synthesis in prophase fermentation. Low DO (10%) is good for MTG accumulation and can prolong the time of cells metabolism in anaphase fermentation. At last, the optimizing (before 32 hour DO30%, after 32 hour DO 10%) results show that MTG reaches 4.72(u.ml-1), 10% higher than DO 30%. Yield coefficient for MTG on carbon substrates (Yp/s) reaches 282.68(u.g-1), 6.2% higher than DO 30%. Yx/s reaches 1.46(g.g-1). The average rate of MTG formation is higher than other DO, reaching0.153u.ml-1.h-1. But the average specific formation rate for MTG is same as other DO.4. We studied the volumetric mass transfer coefficient for transfer across a phase boundary(KLa) and rate consumption of oxygen for cells(QO2) by kinetic method in batch MTG fermentation. The results show that the agitation and aeration have exert great impact on KLa and lower agitation (250rpm) is good for cell growth in prophase fermentation(about 8 hour).5. In this paper, pH 7.0 is good for cell growth; pH 6.4 is good for MTG formation, the optimizing pH (before 16 hour pH7.0, after 16 hour pH 6.4) results show that MTG reaches 4.26(u.ml-1), 33.13% higher than pH 6.4.the rp reaches 0.154(u.mr-1.h-1), the average specific rate of MTG formation reaches 0.036(h-1), Yp/s reaches 249.42(u.g-1), lower than pH 6.4, Yx/s reaches 1.531(g.g-1), lower than pH 7.0.6. The MTG reaches 5.12(u.ml-1) in 41 hour, higher 8.47% than single DO and 20.19% than single pH by optimizing DO and pH.7. We make a research into the exact time and quantities of feeding with glucose and glycerol in flask. Results show that when 1% glucose is fed, it is good for MTG synthesis in 24 hour and when glycerol is fed, it is good for cells growth. Feeding 1 % glucose under pH controlled is better than under pH nature in 24 hour in 10L bioreactor.8. We study effects of feeding rate on MTG synthesis with 1% glucose in 24 hour under pH controlled. It shows that if the feeding rate is higher, and the time that MTG synthesis stopping is longer; the feeding rate is lower, the time that MTG synthesis stopping is shorter and MTG accumulation is more. In this paper, 0.02(L.h-1) or 4(g.h-1) feeding rate is better.9. Based on the principle of magnifying with same aeration and results of MTG batch fermentation in 10L bioreactor, we have an experiment in 50L bioreactor. The results show that MTG is higher 1.64(u.mr-1) than in 10L bioreactor. The average rate of MTG formation is one times more than 10L bioreactor. but the average specific formation rate for MTG, the average rate of cells growth, Yx/s are lower than 10L bi...
|
PDF Full Text Request