Cyanobacteria have been engineered to produce isobutanol directly. what advantage does this have over other alternative biofuels?

Traditionally, energy crops are used for ethanol production thanks to yeast cultures. But, cyanobacteria can naturally ferment alcohol, such as isobutanol, without the need of yeast cultures. Also, cyanobacteria have a fast life cycle, so it can be produced great amounts of isobutanol for a short period of time.