Aerobic hydrocarbon fermentation—a practical evaluation

Abstract

A recent demonstration of the production of yeast from hydrocarbons1.2 has been publicized because of the contribution it might make to the world food problem.3 It is also becoming increasingly evident that end-product accumulation is not completely dependent on the starting substrate,* and that it might be possible to replace some carbohydrate fermentations with hydrocarbon fermentations giving the same product, if the substitution can be justified economically. This communication attempts an evaluation of a general characteristic of aerobic fermentations to assess the relative merits of biosynthesis from hydrocarbon and carbohydrate starting materials.A major factor in aerobic fermentation is oxygen transfer from the gas phase to solution in the proximity of the cell! Although it, can be rationalized that oxygen transfer is the rate limiting step in aerobic fermentations,S this generality has been opposed.? It is considered a reasonable assumption, however, in fermentations such as yeast propagation,? where deBecze and Liebmanns consider aeration the most important factor accounting for 10-2094 of the total production cost.If we accept the premise that in yeast propagation oxygen transfer limits the production rate, then it is pertinent to examine the oxygen requirement of a hydrocarbon fermentation directed at yeast production. In the following calculations these assumptions are made :The composition of the product from the carbohydrate and hydrocarbon fermentations is identical.A typical microbial composition is 47% carbon, C; 6.57, hydrogen, H; 7.5% nitrogen, N ; 8% ashg; and 31% oxygen, 0, by difference.The dry weight yield of yeast from carbohydrate is 5094.9v10The dry weight yield of yeast from hydrocarbon is l0O%,.ltl1

Microbubble fermentation of recombinant Pichia pastoris for human serum albumin production

“…However, it gives no indication of an organism's true oxygen demand as it does not take into account the carbon that is converted into biomass and products. A number of workers (Darlington 1964, Johnson 1964, and Mateles 1971 have used the incorporation of oxygen, carbon, and nitrogen into biomass to predict the oxygen demand for fermentation. They found that a culture's demand for oxygen is very much dependent on the source of carbon in the medium.…”

“…Thus, the more reduced the carbon source, the greater will be the oxygen demand. Darlington (1964) and Johnson (1964) demonstrated that 100 grams of biomass from hydrocarbon requires approximately three times the amount of oxygen to produce the same amount of biomass from carbohydrate. Later, product formation as well as biomass production by oxygen conversion was calculated (Righelato et al, 1968, Cooney 1979.…”

Oxygen transfer in mechanically agitated aqueous systems containing dispersed hydrocarbon

“…(6) (7) With respect to eq. ( 5 ) , it should be noted that a / @ = yl PT/H = Cm, where C, is the final dissolved oxygen concentration in equilibrium with air after infinite elapsed time.…”

“…For the two-phase runs, K L a was then computed from j3 by rearranging eq. (7). For the three-phase runs, KLa* was computed from y1 by combining eqs.…”

“…For the three-phase runs, KLa* was computed from y1 by combining eqs. (7), (14), (15), and (17); the value of KLoao required in the latter two equations was calculated from twophase (liquid-liquid) stirred tank correlation^'-^ using the measured power input ( P / V ) for a particular run.…”