Evaluation of UF and RO in a cellulose saccharification process

The applications of membrane separation within the bioconversion of lignocellulosic materials to ethanol are studied, and this paper reports on cellulolytic enzyme recovery, and reduction of the product inhibition. The conversion of cellulose and hemicellulose to hexoses and pentoses is carried out in a laboratory scale UF-membrane reactor, and the sugars, which have an inhibiting effect on the enzymes, are continuously removed with the permeate. By optimizing the space velocity, the enzyme inhibition is minimized and the rate of hydrolysis is significantly increased.The recovery of the enzymes has also been investigated with regard to their mechanical stability and adsorption on the substrate. Prior to enzymatic hydrolysis, the raw material is subjected to a pretreatment to make the cellulose more accessible to the enzymes, and the effect of the pretreatment can easily be evaluated in the UF-membrane reactor.As a result of the continuous removal of products formed in the hydrolysis, the permeate has a low content of fermentable sugars, and to give the optimal conditions for the fermentation a concentration step is needed. Different RO-membranes are tested in a laboratory scale batch cell to be able to choose a membrane material, fit for filtration in larger modules.