Engineering cellulase activity into Clostridium acetobutylicum.

Clostridium acetobutylicum produces substantial amounts of butanol, and an engineered cellulolytic strain of the bacterium would be an attractive candidate for biofuel production using consolidated bioprocessing. Recent studies have shown that this solventogenic bacterium can be used as a host for heterologous production and secretion of individual cellulosomal components, termed the minicellulosome. Their secretion yields range from 0.3 to 15 mg/L. Nevertheless, it appeared that key cellulosomal enzymes such as family GH48 processive enzymes and members of the large family of GH9 cellulases probably necessitate specific chaperone(s) for translocation and secretion, that is/are absent in the solventogenic bacterium. Heterologous secretion of the latter enzymes, however, can be obtained by grafting specific combinations of scaffoldin modules at the N-terminus of these cellulases, which are then used as cargo domains.