Mix the yeast with the water and sugar and wait a few minutes until it froths, indicating the yeast is alive.
Cut the vanilla bean in half lengthwise, scrape the seeds out with a small knife, and add to the yeast. If using vanilla extract, add it now.
Add the soymilk, the salt, all-purpose flour, and 1 cup of the whole-wheat flour. Knead and add the last cup of whole wheat flour slowly, until you have a resilient but smooth dough, about five to eight minutes.
Place the ball of dough in a bowl coated lightly with oil. Turn over once to coat the top with oil, cover with a kitchen towel, and let the dough rise in a warm place until doubled, about 90 minutes.
Punch the dough down and shape it into an oval. Place in an oiled loaf pan and cover loosely. Let the dough rise until it domes around the top of the loaf pan.
Bake in a 350-degree preheated oven for 50 minutes. Remove to a rack and let it cool for 10 minutes. Then unmold from the pan and continue cooling on the rack.