Lactose sugar unfermentable?

[BigNastyBrew]

Of course...right?

I was just reading some of the differences between S. cervisiae and S. pastorianus and an interesting component grabbed my attention. S. pastorianus is said to have the ability to break down melibiose which is a disaccharide. Lactose sugar is a disaccharide comprised of glucose and galactose. So is melibiose.

Does S. pastorianus have the ability to break down ALL disaccharides or is there some other variable involved? In other words, if I wanted to brew with lactose sugar in a lager, would it ferment out? We know that S. cervisiae cannot. Anyone try this at all?

[ChrisKennedy]

No. Different bonds require different enzymes. Lager yeast can break down certain disaccharides (just like S. Cerevisiae can) but not others. The lactose bond is one that neither can break down, even if the saccharides that make up the disaccharide of melibiose and lactose are the same.

[BigNastyBrew]

Thanks for the response. I was just about to try my own experiment.