A membrane bioreactor for enzyme recovery from saccharification

The present work is part of a bigger project which, as a final goal, has the development and the optimization of a membrane integrated saccharification process for the production of corn based sugar syrups in Cargill plants. Nowadays, the starch saccharification process is mainly performed through a two steps batch bioreactor mediated by hydrolytic enzymes. First, a fast preliminary hydrolysation occurs, where the long polymeric starch chains are cut and of a maltodextrin mixture is produced. Then, the liquified starch is sent to a batch bioreactor where different hydrolytic enzymes, according to the final product type, complete the starch conversion into molecules at low degree of polymerization (DP). The optimisation idea is to use a membrane bioreactor to operate the saccharification in continuous mode, where the enzymes are separated from end products with the help of a selective ultrafiltration membrane. The process under investigation is an innovative technology with high potentiality which could allow not only to increase the reaction yield, but also to save on downstream costs. The Cargill plant of Castelmassa (RO) is taken as reference for this work, in particular, the dextrose line that produces highly concentrated sucrose syrups. Therefore, starting from the currently adopted plant set-up the best operative conditions for a hypothetical plant development with membrane bioreactors will be determined. The experimental work aimed at the optimisation of the membrane filtration stage was performed in the MEMLAB laboratories at DICAM, of the university of Bologna, using a 10 kDa membrane selected from a previous study. The optimisation of reaction conditions was performed in Castelmassa, using the real plant feed to the saccharification stage.