Fatwa ID: 02437
Answered by: Mufti Mohammed Tosir Miah
Question:
In the baking process it is often used yeast, and there is one kind of yeast commercially named here in Italy 'Lievito di birra' (Beer's yeast), it seems it is called 'Brewer's yeast' in English.
I read many fatawa declaring it halal, and I read on encyclopaedia’s and I asked to an Italian Muslim chemist about it and everyone confirmed that it not derived from beer, or any other alcoholic, neither it contains it nor it produces it during the bakery process. Rather it is named 'beer's yeast' because it may be used to make beer, wine or other alcohol beverages if kept in a very sugared liquid for many days at a precise temperature. These conditions are not fulfilled in the bakery process, than it doesn't produce alcohol.
In spite of that there is website called muslimconsumergroup.com where it is written that this yeast is haram because it is a by-product of alcohol beverages and here in my town some brother printed a paper and left it in many copies in the masajid to inform people that this yeast is haram.
Answer
بسم الله الرحمن الرحيم
As there are differences amongst the scholars it is best to refrain from consuming brewer’s yeast. It will fall under doubtful things which the Prophet of Allah 
prohibited from.
It is narrated by Saaiduna Numan Bin Bashir 
who said: I heard the Prophet of Allah say: "Truly, what is lawful is evident, and what is unlawful is evident, and in between the two are matters which are doubtful which many people do not know. He who guards against doubtful things keeps his religion and honour blameless, and he who indulges in doubtful things indulges in fact in unlawful things, just as a shepherd who pastures his flock round a preserve will soon pasture them in it. Beware, every king has a preserve, and the things Allah has declared unlawful are His preserves. Beware, in the body there is a flesh; if it is sound, the whole body is sound, and if it is corrupt, the whole body is corrupt, and behold, it is the heart." (Sahih Bukhari)
Only Allah Knows Best
Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
