Two n's would need a short vowel in front of them
stress-doubleA doubled consonant is the standard English signal for a short stressed vowel. Acuminate has a long stressed vowel and no doubled consonant anywhere in it.
heard asacuminnate
spelledacuminate
saiduh-KYOO-min-ut
One n. acuminate.
English doubles a consonant to show that the vowel before it is short and stressed, as in winner or beginning. The i in acuminate is neither short nor stressed; it is barely voiced at all. So there is nothing for a second n to mark.
Filed alongside
acumanate accuminate acumminate acumunate acyouminate acyoominate
All of them are filed together. All 7 spellings of acuminate.