Submerged Fermentation Conditions

Certain fermentation conditions for fumaric acid are required to obtain high productivity. Among the parameters reported in the literature are pH, morphology, and neutralizing agent. The production media are nitrogen, but not carbon, limited (Goldberg et al., 2006). 

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The process for producing amphomycin comprises cultivating a strain of Streptomyces canus in an aqueous, nutrient-containing carbohydrate solution under submerged aerobic conditions untii substantiai antibacterial activity is Imparted to the solution and then recovering the so-produced amphomycin from the fermentation broth. 

Pleurotus sajor-caju was selected in the present study for the utilization of polysaccharides from corn stalks for production of protein-rich mycelial biomass in submerged fermentation rather than for production of mushrooms (fruiting bodies). Production of mycelial biomass of various mushrooms including morels in submerged cultural conditions is another way to use them as food, food additives or mushroom flavor agents (8,9). 

The original mold observed and preserved by Alexander Fleming was a strain of Penicillium notatum, a common laboratory contaminant. Later, cultures of Penicillium chrysogenum were found to be better producers of penicillin, and the present industrial strains have been derived from this species. The original strains produced the antibiotic only by surface fermentation methods and in very low yields. Improved media and productive strains under submerged aerobic fermentation conditions led to dramatic yield increases. Subsequent improvements, principally in culture selection and mutation, further improved yields, reaching 20-30 g/L. 

The protease fermentation of the Bacillus bacteria takes place under strictly aseptic conditions in conventional equipment for submerged fermentations. The aeration rate is about 1 vvm (volume of air per volume of medium per minute). Vigorous agitation is used to improve air distribution and oxygen transfer. The fermentation temperature is around 37°C, and the time cycle is 2-4 days. 

World War II spurred much advancement in the production of penicillin, particularly the advent of submerged fermentation processes. This new technique was soon adapted to the large-scale production of bacterial proteases. The first modern detergent protease, isolated from Bacillus licheniformis, was introduced in 1962. This enzyme, a particular type of protease called a subtilase, was stable at higher temperatures, had broad substrate specificity and worked well in alkaline conditions. The appearance of this enzyme and others similar to it (i.e., subtilisins) opened up the detergent enzymes market, and by 1969, 50% of the laundry detergent products sold in the United States and Europe contained enzymes. ... 

Microbial rennet may be produced by submerged fermentation of selected strains, eg, the fungus Khi mucor miehei. Various versions of such enzymes have been developed the principal differences are the thermolabiHty of the enzyme itself. This helps cheesemakers develop theic particular type of cheese under local conditions. Products made by recombinant DNA techniques inducing microorganisms to produce chymosin are now being introduced onto the cheese market by Pfizer and Gist Brocades. 

Submerged fermentation can be conducted in different modes of operation. The most traditional is batch fermentation, in which the bioreactor is filled with medium, inoculated and incubated under controlled conditions to the point in which the product (enzyme) has been synthesized to (or nearly to) its maximum level then the cells are harvested for enzyme recovery, if intracellular, or else discarded to recover the medium containing the enzyme, if extracellular. Fed-batch fermentation is a variant of the former in which, after certain time of batch cultivation, the bioreactor is fed with nutrients according to a controlled rate profile and up to a final volume and the product is then recovered as above. This mode of cultivation is particularly appealing for the production of enzymes because it allows the control of the metabolic... 

Microbial lipases are produced mostly by submerged fermentation. Many studies have been undertaken to define the optimal culture and nutritional requirements for lipase production. Lipase production is strongly influenced by a wide range of fermentation parameters such as nitrogen and carbon sources, pH, temperature, agitation, dissolved oxygen concentration and presence of lipids (Elibol and Ozer 2001). A survey of fermentation conditions for the production of bacterial lipases has been reported by Gupta et al. (2004). 

As mentioned earlier, microbial enzymes are produced by submerged fermentation, in which a bioreactor is filled with medium and inoculated with specific microbial cells. The mixture remains under controlled conditions until a sufficient level of prodnction is obtained. If the enzyme is intercellular, the cells need to be harvested for enzyme recovery but in extracellular enzymes, this is not required. Some enzymes can be intracellular in one organism and extracellular in another. For example p-galactosidase (lactase) is extracellular in Penicillium sp. but intracellular in Kluyveromyces marxianus (Stred ansky et al., 1993). In addition, intracellular enzymes can be changed to extracellular by genetic and protein engineering modifications (Geciova et al., 2002). 

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