You can not ignore the alpha channel on the Carbonite it's self. You either have to export those again from Media Encoder as a 24bit instead of 32 bit....
Or you can load it to Media 3 or Media 4 so that only video loads since 3 and 4 have no alpha channel associations.
However -- Note that this does not mean that you are "not loading" the bits...This is a 32bit file so it will still load the "video and Alpha" into memory.
So for efficiency of your Ram Cache you really want to have these as 24 bit. You can use XPression as well to import that as a material put it on the scene director and then put it to the Sequencer. From the Sequencer you can export to images. When exporting you can pick the encode format and that can let you export without Alpha as well.
#Carbonite