Fermentation hydrocarbon substrate

A suitable means of scale-up for aerobic processes is to measure the dissolved oxygen level that is adequate in small equipment and to adjust conditions in the plant until this level of dissolved oxygen is reached. However, some antibiotic fermentations and the production of fodder yeast from hydrocarbon substrates have very severe requirements, and designers are hard-pressed to supply enough oxygen. 

The correlations for as discussed above are for homogeneous liquids. Bubbling gas-liquid reactors are sometimes used for suspensions, and bioreactors of this type must often handle suspensions of microorganisms, cells, or immobilized cells or enzymes. Occasionally, suspensions of nonbiological particles, to which organisms are attached, are handled. Consequently, it is often necessary to predict how the values for suspensions will be affected by the system properties and operating conditions. In fermentation with a hydrocarbon substrate, the substrate is usually dispersed as droplets in an aqueous culture medium. Details of... 

The volumetric coefficient A a for oxygen absorption into oil-in-water emulsions is of interest in connection with fermentation using hydrocarbon substrates. Experimental results [7] have shown that such emulsions can be categorized... 

Erickson, Humphrey, and Prokop (1969) have developed mathematical models which can be used to describe batch growth in hydrocarbon fermentation with two types of dispersed system. In the first type of fermentation, the growth-supporting hydrocarbon substrate is dissolved in inert hydrocarbons, and it is assumed that substrate utilization from the dispersed phase causes little or no change in the interfacial area. 

Single-cell protein (SCP) is the term that refers to protein in a variety of microbial cells, which are produced by fermentation using hydrocarbon substrates. The typical protein content of these microor nisms is 6070% in bacteria, 4565% in yeasts, and 3540% in mold after separation and drying [3]. When... 

Figure 5 shows some data referring to the ability of biosurfactant to emulsify kerosene produced by B. subtilis ATCC 6633 at the different substrate concentrations tested (5, 10, 20, and 40 g/L). Besides a decrease in surface tension, stabilization of hydrocarbon/water is frequently used as an indicator of surface activity. Note, however, that the quantity of biosurfactant produced should not be related to the E24 because that is an intrinsic property of the molecule. A similar behavior of the emulsifying activity in relation to the carbon source concentration and to the incubation period has been observed. The diverse initial concentrations of commercial sugar studied favor the formation of a surface-active compound, with an emulsifying activity >50% in a 48-h process. The maximum values for emulsion activity of 57.9 and 56.9% were determined for 10 and 20 g/L of substrate, respectively. It should be emphasized that there was a reduction in the E24 after a 96-h period of incubation. Carvalho et al. (36) reported similar results for cell-free fermented broth by Bacillus sp. emulsified in kerosene. 

It is doubtful that cellular models of any greater complexity will have much utility in soluble substrate fermentations.However, another level of complexity may be warranted in insoluble substrate fermentations such as hydrocarbons and cellulose. 

A dramatic rise of the cost for liquid and gaseous hydrocarbons stimulates development of novel biopolymers which production is not depended on fossil fuels. Fermentative biosynthesis of poly(3-hydroxybutyrate) [PHB] and its homologues - poly(3-hydroxyalkonoates) [PHAs] bases on using renewable organic substrates. Hydrocarbons wastes of food- and wine/juice industries (sugars, melissa, starch et al.) present the basic structural material for bacterial PHB (and PHA). Utilization of hydrocarbons dining biosynthesis of PHA is favorable to eco-efficiency. 

Substrate transfer plays a very special role in the three-phase system of hydrocarbon fermentation. In principle, there are two ways in which the substrate may have access to the organism. 

Fig. 14. Primary recovery scheme of cells from fermentation broth using hydrocarbons as substrate (Wang, 1968)...

For 20 years prior to those mid-50 s, there had been an established, and growing, industrial fermentation industry, based mainly on the use of blackstrap molasses as a substrate. Then, beginning the hydrocarbon age, there came the petrochemicals, derived from the ever-so-cheap barrel of crude. The byproducts of the petroleum industry had unlimited promise for chemical productions. Olefins and the polymers were starting their boom. Everything grew bigger, very rapidly. Everyone took it that the cheap barrel of crude would, like diamonds, be forever. As for the fermentation industry - it was a case of "off with old, and on with the new". Hence, the statements like that of Hastings. 

In addition to molds, yeasts are also known to produce large amounts of CA from various carbon sources.CA production by yeasts was used commercially during the 1960s and 1970s, when n-alkanes and hydrocarbons were relatively inexpensive. Nowadays, Y. lipolytica is widely used yeast for its ability to produce large amounts of CA from various substrates. One disadvantage of yeast fermentation is that they produce substantial quantities of unwanted by-product isocitric acid. 

Oxidation of different substrates. We found (Vorobjeva, 1959) that glycerol can be used as a sole carbon source by P. jensenii only under aerobic conditions. If fumarate was added to minimal medium, then glycerol fermentation proceeded under anaerobic conditions with fumarate acting as an electron acceptor. Propionibacteria can oxidize compounds more reduced than glycerol, namely, alkanes and long-chain primary alcohols (Table 3.1). Oxidation of hydrocarbons is suppressed by the inhibitors of cytochrome oxidases, NaNa (10 M) and KCN (10" M), respectively, by 88 and 96%, which is similar to the degree of inhibition observed for glucose oxidation by P. pentosaceum. 

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