Naturally occurring microorganisms

Complementary work by the GE team on Hudson River sediments has utilized a microcosm system to understand better both the aerobic and anaerobic transformations that occur in stationary sediments. These studies provided further evidence that the naturally occurring microorganisms shown in the Hudson River field trial have the potential to attack Aroclor 1242 at rapid rates both aerobically and anaerobically. These results are helping to further our understanding of the fate of released PCBs in river sediments (Fish Principe, 1994). 

A more efficient and simple bioreduction system, which avoids the problems with the system involving naturally-occurring microorganisms or cell-free systems described above, has been required. A novel bioreduction system, in which Esherichia coli transformant cells coexpressing the genes of an NAD(P)H-dependent carbonyl reductase and GDH, as a cofactor regenerator, were used as the catalyst, has been constructed (Kataoka et al., 2003). The production of chiral CHBEs is a typical successful example with this bioreduction system. 

The ASTM defines a biodegradable plastic as a degradable plastic in which the degradation results from the action of naturally occurring microorganisms such as bacteria, fungi and algae. 

Bioremediation in engineered systems can be used for removal of MTBE from groundwater. There are also naturally occurring microorganisms which have been shown to completely mineralise MTBE under aerobic conditions. Several pure strains that have been isolated and studied can mineralise MTBE. They do so by direct metabolism, whereby, MTBE is used as the sole carbon and energy source [15,21-25]. 

OPP has addressed these atid similar questions oti a case-by-case basis iti its risk assessments. To answer these questions, EPA hcis normative data requirements and test methods developed for naturally occurring microorganisms. Use of these tests (or tiered series of tests) enable the Agency to to establish whether the effect of concern is likely to materialize under field conditions. In some cases, applicants have addressed questions by revising the conditions of the proposed test or by modifying the test microorganism to minimize potential risk. 

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