Equil. aspects in biotechnol. and thermodn. as the main theory underlying them have thus far received relatively little attention. As a consequence, design and development of biotechnogical processes is still carried out today in an relatively empirical way. For this situation to improve, a wider and more systematic use of the thermodn. aspects pertaining to biotechnol. must be encouraged. Recognizing this need, the ESF program on Process Integration in Biotechnol. developed an intensive advanced course which was held twice so far. The present contribution uses the course structure in order to give a short overview of the field and to identify research needs. The development of a rigorous thermodn. description, for the exceedingly complex world of biotechnol., is indeed one of the major challenges today in establishing the scientific basis for rational efficient, and fast bioprocess development and design. [on SciFinder (R)]