NOVELTY - A method for degrading a plastic is in the presence of a biosurfactant using recombinant microorganisms, is new.    USE - The method is for the degradation of (waste) plastics and also applicable in producing useful substances simultaneously e.g. proteins, metabolites and biosurfactants particularly alpha-amylase (claimed).    ADVANTAGE - The method is efficient and safe to enable removal of environmental pollutants on large scale with simultaneous production of useful substances.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a method for degrading a plastic by contacting the plastic with a microorganism;    (2) a process for producing useful substances from a plastic which comprises degrading the plastic by contacting with a microorganism and further converting components of the thus degraded plastics with use of a microorganism;    (3) a method for degrading a plastic by contacting the plastic with a microorganism in the coexistence of a biosurfactant and/or a plastic-degrading enzyme and thus degrading such plastic through the action of the microorganism;    (4) a transformant microorganism obtained by recombining a DNA that contains a gene encoding a surface-active substance, a DNA that contains a gene encoding a plastic- degrading enzyme or/and a DNA that contains a gene encoding a useful substance;    (5) a DNA containing a base sequence that encodes:    (a) a polypeptide identical or substantially similar to that of (III) with 105 amino acids; or    (b) one based on the sequence of (III) but with some amino acids deleted, substituted or added and practically functionally equivalent to hydrophobin;    (6) another DNA containing a base sequence of (III) with 318 base pairs or a part of it, or one hybridizable with a DNA containing a base sequence complementary with that of the already-specified DNA under stringent conditions and having practically identical function as such DNA;    (7) a similar DNA containing a base sequence that encodes:    (a) a polypeptide identical or substantially similar to that of (IV) or (V) with 224 or 259 amino acids; or    (b) one based on the sequence of (IV) or (V) but with some amino acids deleted, substituted or added and practically functionally equivalent to a plastic-degrading enzyme;    (8) a DNA containing a base sequence of (IV) or (V) with 675 or 780 base pairs or a part of it, or one hybridizable with a DNA containing a base sequence complementary with that of the already-specified DNA under stringent conditions and having practically identical function as such DNA;    (9) a DNA containing a base sequence that encodes:    (a) a polypeptide identical or substantially similar to that of (VI) with 174 amino acids; or    (b) one based on the sequence of (IV) or (V) but with some amino acids deleted, substituted or added and practically functionally equivalent to a plastic-binding protein;    (10) a DNA containing a base sequence of (VI) with 525 base pairs or a part of it, or one hybridizable with a DNA containing a base sequence complementary with that of the already-specified DNA under stringent conditions and having practically identical function as such DNA; and    (11) proteins encoded by these genes.