People with thin skins don't last too long on the forum. Relax. I am going to eliminate both reports you've made.
You screwed up and used too much nitric and now you must pay the piper. Either drop the precious metals with copper and start over or evaporate the solution down to eliminate the excess nitric. Both methods are dealt with on the forum. Study the forum and forget the yeast. No one here and no one on the internet, that I can find, has heard about using it.
Never pre-mix the nitric. Instead, in general:
(1) Cover the material with HCl. Heat to about 60C
(2) Add a small amount of nitric.
(3) When it stops fizzing and reacting, add another small quantity of nitric. Repeat.
(4) When an addition of nitric produces no reaction, don't add any more nitric
To get an idea of how much acid it will eventually take. For about 31g of karat gold, pure gold, copper, etc., it will take about 125ml of HCl and about 25ml of HNO3.
Details on this and every other process on the planet can be found on this forum. Search and see.