The rule that min b'sh'eino mino requires bitul b'shishim rather than bitul b'rov, is this d'rabbanan or d'oraisa?
If your question is if the taste that comes out of an item needs sixty times it size to nullify it min haTorah, then your question really is, is Ta"am k'ikur M'Dioraysa.
That is a three way Machlokes in the Rishonim, based on the Gemorah in Pesachim 44b,
(1) it is from the Torah and you would get the same punishment as the original forbidden food,
(2) it is from the Torah but you do not get malkus on just the taste, or
(3) it is only m'dirabonon.
Here is how the sefer קובץ יסודות וחקירות summarizes it:
When a forbidden substance becomes mixed with a permitted substance of another type, [it causes it to become forbidden] if its flavor can be detected...
What is implied? When the fat of the kidneys falls into beans and becomes dissolved, the beans should be tasted. If the taste of fat cannot be detected, they are permitted. If [not only] the taste, [but also] the substance of the fat is present, they are forbidden according to Scriptural Law. If the flavor could be detected, but there is no substance, they are forbidden by Rabbinic Law.
In paragraph 3 Rambam goes on to define what he means by ‘substance’, and in paragraph 30 to discuss what to do if there is no one available to taste the suspect mixture (which often involves estimating based on a ratio of 1:60).