Energy sources of microorganisms

The source of microorganisms and CP-degradation kinetics are key factors in on-site systems. Development of specific microbial cultures for bioremediation of CPs may involve pure and enrichment culture approaches. The approach of isolation and mass cultivation, followed by inoculation of the treatment system, has been applied to systems using, for example, Flavobacteria (O Reilly Crawford, 1989) and Rhodococci (Valo et al., 1989). The Flavobacterium-based processes sometimes involve addition of supplemental carbon and energy sources during CP treatment. 

The breakdown of xanthine by Clostridium addiurici and C. cylindro-sporum is of interest not only because this purine can be the sole energy source of these microorganisms, but also because many of the intermediates of this pathway resemble dephosphoribosylated intermediates of the pathway of purine biosynthesis de novo. 

Triazines pose rather more of a problem, probably because the carbons are in an effectively oxidized state so that no metaboHc energy is obtained by their metaboHsm. Very few pure cultures of microorganisms are able to degrade triazines such as Atrazine, although some Pseudomonads are able to use the compound as sole source of nitrogen in the presence of citrate or other simple carbon substrates. The initial reactions seem to be the removal of the ethyl or isopropyl substituents on the ring (41), followed by complete mineralization of the triazine ring. 

Owing to diminishing fossil fuel reserves, alternative energy sources need to be renewable, sustainable, efficient, cost-effective, convenient and safe.1 In recent decades, microbial production of ethanol has been considered as an alternative fuel for the future because fossil fuels are depleting. Several microorganisms, including Clostridium sp. and yeast, the well-known ethanol producers Saccharomyces cerevisiae and Zymomonas mobilis, are suitable candidates to produce ethanol.2,3... 

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