Because plant based sources for the production of biofuel are limited and are competing with food production, alternative sources are investigated. One such alternative is the development of microbial fermentation using bulk industrial waste streams as e.g. from forestry and paper industry as starting material. The research goal within this  cooperation is to find alternative, improved cell-factories for the fermentative production of butanol. This will be done by (i) metabolic engineering and physiological optimization of the well-known acetone-butanol fermentation by Clostridium acetobutylicum and some related Clostridium species, and (ii) selection and development of other butanol cell factories from the different biological platforms available within the Kluyver Centre. This will include selection of Sacharomyces cerevisiae, Bacillus subtilis and several lactic acid bacterial strains with high butanol-tolerance (more than the reported tolerance to 2% butanol of Clostridium acetobutylicum) and using these, and the solvent-tolerant Pseudomonas putida, as hosts for introduction or improvement of butanol-producing pathways.