a novel modified thermoplastic starch is manufactured from a native starch using a polysaccharide produced by the fungus species ophiostoma ulmi , by growing a culture in a yeast extract medium ; adding the native starch ; mixing , and harvesting the modified thermoplastic starch . the modified thermoplastic starch may be used in the manufacture of a biodegradable plastic which exhibits low water absorbency and high tensile strength . the plastic may be used to manufacture films or moulding products by casting , extrusion , injection , or compression techniques .