Saccharomyces cerevisiae strains do not provide the amylase enzyme necessary to break down and hydrolyze pure starch molecules. Best as I can tell, the same is true wrt Brettanomyces. There are articles extant showing when amylase producing genes are cloned into sac c. yeast it actually becomes highly capable of converting raw starches into ethanol for the purposes of fuel production. I imagine the same would be true of Brett...
Cheers!