Dissolve yeast in warm water; set aside.
In a bowl, combine flour, whole wheat flour, wheat germ, brown sugar, salt, sliced banana, creamy peanut butter, and egg. Add the yeast mixture and knead until smooth and satiny, about 10 minutes. Allow to rise, covered, in a warm place for 2 hours.
Punch down; place in a greased loaf pan, and allow to rise until doubled in bulk, about 1 hour.
Bake at 350*F, for 20 to 30 minutes, or until golden brown.