Fermentation Products: Physiological and Bioenergetic Considerations
The overproduction of substances by microbial cultures is discussed in a bioenergetic context. Since many fermentation products are generated by energy-yielding reactions, it is clear that the rate of energy consumption of a cell will influence the rate of product formation. It is shown that the nature of the growth environment influences to a great extent the magnitude of these energy-consuming reactions. On the other hand, the energetic efficiency of the energy-generating reactions can be reduced and this will lead, assuming the same rate of energy consumption, to an increased rate of product formation. Another class of products, in particular proteins, can only be produced by energy-consuming reactions. Therefore, the extra energy consumption caused by the overproduction of proteins is in direct competition with the energy consumption that the cell requires for maintenance and growth. The physiological implications of this metabolic conflict are discussed and it is suggested that this type of overproduction will be inherently unstable, unless the overproduction of a protein increases the fitness of the producer organism.
KeywordsBiomass Fermentation Magnesium Manganese Respiration
Unable to display preview. Download preview PDF.
- (2).Dawes, E.A., and Senior, P.J. 1973. The role and regulation of energy reserve polymers in micro-organisms. In Advances in Microbial Physiology, eds. A.H. Rose and D.W. Tempest, pp. 135–266. London: Academic Press.Google Scholar
- (8).Neijssel, O.M.; Hardy, G.P.M.A.; Lansbergen, J.C.; Tempest, D.W.; and O’Brien, R.W. 1980. Influence of growth environment on the phosphoenolpyruvate: glucose phosphotransferase activities of Escherichia coli and Klebsiella aerogenes: a comparative study. Arch. Microbiol. 125: 175–179.PubMedCrossRefGoogle Scholar
- (10).Neijssel, O.M., aad Tempest, D.W. 1979. The physiology of metabolite overproduction. In Microbial Technology: Current State, Future Prospects, eds. A.T. Bull, D.C. Ellwood, and C. Ratledge, 29th Symposium of the Society of General Microbiology, pp. 53–82. Cambridge: Cambridge University Press.Google Scholar
- (16).Sikyta, B.; Kyslík, P.; Voleský, B.; Pavlasovâ, E.; and Stejskalová, E. 1982. Over-production of endoenzymes in Escherichia coli - selection of hyperproducing strains in a chemostat. In Over-production of Microbial Products, eds. V. Krumphanzl, B. Sikyta, and Z. Vanek, pp. 593–599. London: Academic Press.Google Scholar
- (18).Tempest, D.W.; Dicks, J.W.; and Hunter, J.R. 1966. The interrelationship between potassium, magnesium, and phosphorus in potassium- limited chemostat cultures in Aerobacter aerogenes. J. Gen. Microbiol. 45: 135–146.Google Scholar