Methods for the economical production of biofuel from biomass

A method for producing distillers dried grains obtained from a fermentation process for the production of isobutanol, said method comprising:

• (a) cultivating a yeast biocatalyst in a fermentation vessel containing a culture medium comprising at least one carbon source to produce isobutanol, wherein said yeast biocatalyst is engineered to express exogenous genes encoding an acetolactate synthase, a ketol-acid reductoisomerase, a dihydroxy acid dehydratase, a ketoisovalerate decarboxylase, and an isobutyraldehyde dehydrogenase;
• (b) removing at least a portion of an insoluble material from the fermentation vessel after isobutanol is produced, wherein said insoluble material comprises said yeast biocatalyst;
• and
• (c) drying said insoluble material comprising said yeast biocatalyst to produce the distillers dried grains.