Question

cyanobacteria have been engineered to produce isobutanol directly what advantages does this have over other alternative biofuels

Answer 1

The advantage that engineered cyanobacteria have over other alternative bio fuels is that IT AVOID MULTIPLE PROCESSING STEPS.
Bio fuels are liquid fuels that are derived from waste plants and animal matters. Production of bio fuels involves many steps. Withe the advance of engineered cyanobacterial, multiple production steps can be avoided during the manufacturing of bio fuels. 

Answer 2

b. Multiple processing steps can be avoided.