From biofuel to bioproduct: is bioethanol a suitable fermentation feedstock for synthesis of bulk chemicals?

The first pilot-scale factories for the production of bioethanol from lignocellulose have been installed, indicating that we are on the brink of overcoming most hurdles for an economically feasible process. When bioethanol is competitive as biofuel with fuels originating from petrochemical resources, it will also become interesting to use lignocellulose as a feedstock for the fermentative synthesis of bulk chemicals. Lignocellulose hydrolysates, however, are highly complex and viscous media, posing challenges to oxygen transfer, product formation at low sugar concentration, product recovery, etc. Bioethanol is an exceptional product in this respect because it can be produced anaerobically, at low sugar concentrations, and can be easily removed from the broth by distillation. For products that do not have these benefits, another approach may be interesting, in which lignocellulose is first converted to bioethanol, which in turn serves as a substrate for a second conversion into the desired product, similar to the traditional production of acetic acid in vinegar. In this perspective, we compare these one-stage and two-stage conversions with respect to overall yield and productivity of the fermentation process and the differences that occur in product removal. (C) 2011 Society of Chemical Industry and John Wiley & Sons, Ltd