Question:
The officer took my license and served me with a notice of suspension after the breath test: How can he do that if I'm presumed innocent?

Answer:
Agreed, it is blatantly unfair. But the law in most states having a "per se" statute (see question #10) provides for immediate suspension and confiscation of the license if the breath test result is above the legal limit (or, in the case of a blood or urine test, if the officer reasonably believes the result will be above the limit).