TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Degradation Methods: The biosurfactant is particularly a plastic-binding protein. Such plastic-degrading enzyme is for decomposing a plastic. The biosurfactant has an effect in adsorbing onto the plastic to enhance hydrophobic interaction between them, under the conditions of which the biosurfactant and plastic are mixed, particularly in a low moisture-activation stat, and optionally high salt concentration state, for their mixing and in a high moisture-activation sate, and optionally low salt concentration state, for the plastic-degrading enzyme to decompose the plastic. Such plastic is allowed to contact with Aspergillus oryzae or Aspergillus sojae, so that their produced biosurfactant and plastic- degrading enzyme can act on the plastic for degradation. The useful substances can be proteins, primary and secondary metabolites or biosurfactants, which are substances secreted to outside of the microorganism. A transformant microorganism is obtained by recombining a gene that encodes a gene relating to the biosynthesis of a useful substance for high expression of such enzyme. The plastic degradation is promoted by the coexistence or externally adding of such surface-active substance and/or plastic-degrading enzyme, or by using a transformant microorganism obtained by recombining genes that encode the biosurfactant and/or plastic-degrading enzyme for highly expressing them, and the genes are under the regulation of a structural expression promoter, or inducible expression promoter. Such surface-active substance used is preferably a biosurfactant. The biosurfactant and/or plastic-degrading enzyme are originated from a fungus of Aspergillus genus, e.g. Aspergillus oryzae. Such plastic-degrading enzyme can be esterase, protease, peptidase, lipase, cutinase, serine hydrolase or their mixture.Preferred Transformants: The surface-active substance is particularly an Aspergillus oryzae-originated hydrophobin, with the plastic-degrading enzyme being an Aspergillus oryzae-originated cutinase, and the useful substance being alpha-amylase. A biosurfactant such as hydrophobin and plastic-degrading enzyme e.g. cutinase are used.    TECHNOLOGY FOCUS - POLYMERS - Preferred Degradation Methods: Such plastic is particularly a biodegradable plastic, e.g. polyester, polyurethane, polypropylene, polyvinyl chloride, nylon, polystyrene, starch and their mixture. The polyester is selected from polybutylene succinate, polylactic acid, poly(partial butyl succinate adipate), aliphatic polyester and polycaprolactone. The plastic can be one of the essential elements in a composite material.    TECHNOLOGY FOCUS - BIOLOGY - Preferred Degradation Methods: The microorganism is a mycelioid, e.g. Streptoverticillium of Streptomyces genus including Streptomyces glyceus and Streptomyces selicolor. Such microorganism can also be a eukaryotic mycelian fungus, e.g. of genus Aspergillus, Penicillium, Trichoderma, Rhizopus, Magnaporthe, Metarhizium, Neurospora, Monascus, Acremonium or Mucor, including A. oryzae, A. sojae, A. nidulans, A. tamari and A. repens. The plastic is allowed to contact with such microorganism in a liquid culture system, or through contact of Aspergillus oryzae with a plastic in a solid cultures system.Preferred Transformants: Such transformant is a microorganism belonging to genus Aspergillus, particularly originated from Aspergillus oryzae. EXAMPLE - A plastic e.g. polybutadiene styrene film was allowed to contact with Aspergillus oryzae in a fortified emulsion minimal medium while culturing, or with added cutinase and/or hydrophobin. The degradation was confirmed.