The multidisciplinary PASS-BIO project aims to establish a suitable, cost-efficient bioreactor module for the flexible conversion of a wide variety of feedstock to produce either short-chain carboxylic acids in an acidic fermentation or methane as alternative. The module should be designed according to the principle of plug flow. Although this technology is not new, its full potential in terms of process robustness is not exhausted compared to the round stirred tank reactor. Intensified monitoring to control the formation of spatial gradients along the reactor lengh is used to implement autonomous operation, even for inexperienced users. The project aims to identify suitable substrate mixtures, enzymes to support the process, and optima for blending different substrates. In addition, the use of the end products of acid fermentation as starting material for the biotechnological production of the polyunsaturated fatty acid docosahexaenoic acid will be evaluated. The whole upstream process shall be made easier and reliable for fast adaptation as a contribution towards smart bioproduction grids.