Computational methods Ethanol

Computational methods can also be focused on one selected pathway with finer detail, as opposed to the broad-sweeping computational methods described in Section 18.2.1.3. A kinetic model of xylose utilization by S. cerevisiae for ethanol production aimed to identify which portion of the poorly functioning pathway should be improved [85]. This analysis concluded that higher xylulokinase activity was needed. The authors experimentally verified that increasing xylulokinase activity via the expression of the E. coli xylB improves ethanol production and xylose consumption [85]. Since this initial report, a variety of other studies have reported strategies for increasing xylulokinase activity that also improve xylose utilization [86, 87], including those implemented in the thermotolerant yeast Hansenula polymorpha [88]. 

A suggested procedure would be equal volumes of the sample and a 4% (by volume) benzene in pure ethanol. This is easily set up using a G.C.-Computer system Note Ethyl Acetate can also be detd by Standard Method ASTM Designation DI617—69, described here under Ethyl Acetate 4.3.10 Methyl-isobutyl-kefone (MIBK). The rest is iisted but not described in MIL-E-463B, but it seems that the Test 4.6.1.8 for determination of Acetone and other ketones, described... 

The first persons to point out the possibility of computer monitoring of indirectly measured parameters were Yamashito, Hisashi, and Inagaki in 1969 (2). The method was described in a U.S. Patent in 1975 (3). Examples of the application of computer-aided indirectly measured parameters to the control and optimization of batch-fed Baker s Yeast fermentation were described by Jefferis and Humphrey in 1973 (4) and by Wang, Cooney, and Wang in 1977 (5). Background and detailed history of this application can be found in the review by Humphrey (1). The work to be discussed in this report is another example of computer-aided indirectly measured cell biomass and growth rate and the use of this information in the feed back control of the carbon substrate, ethanol, in a process for the production of a yeast single cell protein (SCP). 

The use of digital computers to carry out complete calculations in the design of separation processes has been the goal of many. To do this effectively, suitable methods for phase equilibria and tray-to-tray distillation calculations are required. Results calculated by the application of such methods to dehydrate aqueous ethanol mixtures using ethylene glycol as the extractive distillation solvent is discussed below. A brief review of the methods used for phase equilibria and enthalpies is followed by a discussion of the results from distillation calculations. These are compared for extractive distillation with corresponding results obtained by azeotropic distillation with n-pentane. 

The methods used here to give the phase equilibria are reviewed, and the Azeotropic Distillation Program ADP/ADPLLE is described. Application of the program to calculate an azeotropic distillation problem is shown and discussed, and a sample computer output is given and is briefly discussed. Finally, calculated azeotropic distillation results are compared for dehydrating aqueous ethanol for the three entrainers, n-pentane, benzene, and diethyl ether. 

Special consideration is given to the effect of completely miscible cosolvents such as methanol and ethanol. A new approximate method of predicting cosolvent effects is presented. The results should be useful in supplying necessary phase equilibrium data to complex computer programs for modeling transport and fate of sparingly soluble organics in the environment. 

Since the assumptions given by Eq. (13-16) become approximations for highly nonideal solutions such as ethanol and water, nG and nL become only approximately equal to riG and n L, respectively. Thus, some disagreement in the yji s predicted by use of the two types of efficiencies might be expected. The error in the y 1 s resulting from setting n G — nG and n L = nL appears to be small relative to the precise method used to compute the m s. 

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