1,4-.alpha.-D-Polyglucan-based thermoplastic mixture, process for the preparation and use thereof The present invention relates to a thermoplastic mixture based on biopolymers obtainable by preparing and mixing (A) 100 parts by weight of a biocatalytically produced 1,4-.alpha.-D-polyglucans, (B) up to 400 parts by weight of a melt-processable polymeric material different from (A), (C) water in an amount sufficient for plastification of the mixture, (D) at least one plasticizer in an amount of 10 parts by weight up to half the total of the parts by weight of (A) and (B), and (E) where appropriate up to ((A)+(B)) parts by weight of other conventional additives, where the water content of components (A) and (B) has been corrected to zero by calculation where the plastification takes place with introduction of thermal and mechanical energy, to the use of the mixture for producing essentially biodegradable moldings and sheets, and to a process for preparing the mixture.