New Two-Step Fermentation Process

Though the classical two-step fermentation process achieved very high yield of l-AA, it needed an additional hydrogenation step to convert D-glucose to D-sorbitol. Therefore, the direct fermentation of D-glucose to 2-KLG is also an interesting topic. There have been attempts to introduce an additional step to convert D-glucose to D-sorbitol. However, the lack of an enzyme that can 

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Compared to the classical two-step fermentation process, the new two-step fermentation process-based one-step process could further ehminate the cost of hydrogenation of D-glucose to D-sorbitol. Based on the two-step fermentation process, Anderson et al. expressed a 2,5-DKG reductase from Corynebacterium ATCC 31090 in E. herbicola ATCC 21988. The recombinant E. herbicola strain could accumulate 1 g 1 of 2-KLG from saturated D-glucose solution [31]. Using protoplast fusion of an E. herbicola and a Corynebacterium strain, the resulting strain could produce 2.07 gl of 2-KLG [40]. According to the limited literature in the public domain, the new two-step fermentation process-based one-step process seems to be less efficient than the classical two-step-based process. 

It is important to note that, though it has been reported that the new two-step fermentation process-based one-step process could accumulate more than 100 gl of 2-KLG, there is no public information available that can substantiate this claim [41]. 

Therefore, an innovative two-step fermentation process were discovered to resolve this problem. In the new innovative two-step fermentation process, the D-glucose was converted into 2,5-diketo-gluonic acid (2,5-DKG) by Erwinia herhicola ATCC 21988 or some similar strains with glucose dehydrogenase, gluconate dehydrogenase... 

Fundamentally new insights have recently been gained by Kluyver and Schnellen. Making use of a pure culture of methane bacteria, Methanosarcina Barkerii, they converted a mixture of carbon monoxide and hydrogen into methane according to the equation CO - - 3 H2 = H2O -F CH4. This fermentation process actually takes place in two steps (a) CO + H2O = H2 - - CO2 and (b) CO2 + 4 H2 = 2 H2O - -CH4. Many details and references to the older literature can be found in this publication and also in the thesis of Schnellen. ... 

Synthesis of vitamin C (ascorbic acid) is conventionally performed via the Reichstein-Griissner procedure, which involves the fermentation of glucose followed by five chemical steps. Cerestar/ BASF recently developed a new process that consists of one fermentation step and two simple chemical steps (via 2-keto-L-gluconic acid). It is predicted that soon a fermentation process will be developed to convert glucose into vitamin C in a single step, eliminating several recovery steps and reducing extraction solvents. 

A. vinelandii UWD and W. eutropha were grown in a two-step process, employing a pre-culture and a polymer medium. For PEG and DEG modulated fermentation, A. vinelandii UWD was used. After 48 h of growth, 10 vol.% of the pre-culture were used as inoculum for the polymer medium, which was harvested after 24 h (12). Both media were amended with 2.0 wt % of the respective PEGs. It is noteworthy that A. vinelandii UWD must be grown in the presence of 20 mg/L rifampicin, in order to prevent the back mutation of the engineered strain to the A. vinelandii UW parental strain genotype, which is not resistant to the antibiotic. All fermentation experiments were conducted in a shaker-incubator (New Brunswick Scientific) at 30 °C and 180 rpm. Cells were... 

Texture In the figure 2 the values of firmness along the process for two consecutive seasons is shown, very similar results were found for both seasons. The most important decreases took place during the lye treatment and subsequent wash step, reaching values of 50% of the initial. When the fruits were placed in the brine solution the firmnes recovered to 80% of the initial and, finally, during fermentation there was a new decrease to 60% of the initial. 

In the 1940 s, in addition to these operations, two other processes became important. Acetic acid was made by reacting methanol with carbon monoxide, and acetic anhydride was being made by the ethylidene diacetate process, which in effect is the dehydration of acetic acid to the anhydride by the use of acetylene. Fermentation ethyl alcohol was converted to acetic acid via acetaldehyde as well as by the direct oxidation of ethyl alcohol. A new operation on the Gulf Coast was also based on acetaldehyde. However, the acetaldehyde is made by the direct oxidation of liquefied petroleum gas. A further process for the production of these materials, in which acetaldehyde is oxidized in one step to a mixture of anhydride and acid, was also begun. 

Figure 19.20. Flowsketches of two processes employing fermentation, (a) Process for enzyme production, showing the use of growing trays, growing drums and stirred tank. Purification steps are the same for all three modes of culture growth, (b) Production of methane-rich gas by anaerobic digestion of finely divided waste solids in a 10-20% slurry. Residence time in the digester is five days [D.M. Considine (Ed.), Energy Technology Handbook, McGraw-Hill, New York, 1977].

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