Your need to find a supervisor at your of a nearby institute. Many students have done theses on plastic polymers microbes facilitated degradation.

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You can 1st find for articles and thesis in pollution and micropolluants in Iran's coastal waters and in the world.....

Dear sir;

thanks for your consideration.actually i found some articles and read them.my proposal is almost done

You have to choose a supervisor at your institute who shall guide you. Many publications are available on plastic degradation which is an inefficient process. Be humble in asking for suggestions.