Artisan bread requires a very small amount of yeast due to the longer rising process it is put through. The longer the rise, the more fermentation occurs which means there is a lot more flavour in the final loaf. Yeast uses the sugar to rise so any more than a tiny amount of yeast will mean the dough rises too much over the 3-4 hours' time period and will then collapse. The smaller the amount of yeast, the longer it takes to use all the sugar which means by the end of the rise there is more flavour left in the dough. The mixture is usually wetter than conventional dough which helps create the glucose needed to sustain the long rise.
Please click here for a recipe for making artisan dough with your BM450 bread maker.