1. Clostridium thermocellum JN4 and Thermoanaerobacterium thermosaccharolyticum GD17 - Lactate to butyrate
2. Caldicellulosiruptor saccharolyticus and Rhodopseudomonas palustris - Acetate
3. Saccharomyces cerevisiae and Escherichia coli - formate
4. Amino acids exchange using combined dark- and photo-fermentation