Our "apprenticeship" means we have sat in on yeast lectures and shadowed brewers for a day ( but admit to experiencing a few zeds from zymamonas (an anaerobic bacteriun causing slimy gelatinous threads in beer) and zymase, a mixture of enzymes extracted from yeast which causes the alcoholic fermentation of sugars.
A Vin Doux Naturel is a lightly fortified wine, whereby the addition of grape spirit arrests the alcoholic fermentation, leaving naturally sweet grape sugars, but increasing the alcoholic strength to around 15.