DEFINED COIMMOBILIZATION OF MIXED MICROORGANISM CULTURES

Specifically selected organisms bound in close proximity can be an effective means of optimizing biotransformations that exploit complementary metabolic activity. A review of the literature gives the advantages as, primarily, controlled sequential conversions (e.g., in steroid, alcoholic beverage, or hydrogen production) or simultaneous metabolism of a multicomponent medium (e.g., in waste degradation and remediation). The local oxygen environment can also be manipulated by incorporating photosynthetic organisms for in situ generation, or conversely to provide a gradient, by binding aerobes externally to anaerobes to generate internal oxygen limitation. Of the two broad categories for physical immobilization, adsorption and encapsulation, the latter dominates reported work. The commonest immobilizing medium is calcium alginate. Mechanisms influencing the association of two or more different organisms are, however, rarely researched in comparison to single-cell or enzyme immobilization.