In this third batch I used the same protocol of cooking and mixing but placed the cultured beans in a bread-pan (about 4 inches deep) and created 'air channels' in the beans with sterile utensils.

It turned out pretty well. Digging into the lower beans revealed a really good cover of bacteria. The top beans dripped off or dried early in the incubation so they did not have any growth on their superior surface.

I dug into the bottom-right corner of the breadpan and found consistent gooey beans.

I googled Bacillus subtilis to learn more about it and came across "MicrobeWiki", a very informative site about the characteristics and capabilities of a host of microbes. Under its B. subtilis entry I learned:

"Bacillus subtilis bacteria use their flagella for a swarming motility. This motility occurs on surfaces, for example on agar plates, rather than in liquids. Bacillus subtilis are arranged in singles or chains. Cells arranged next to each other can only swarm together, not individually. These arrangements of cells are called 'rafts'. In order for Bacillus subtilis bacteria to swarm, they need to secrete a slime layer which includes surfactin, a surface tension-reducing lipopeptide, as one of its components (Schaechter 2006)."

Since it moves so readily on surfaces, that could explain why it is so quick to cover the soybeans, presumably monopolizing the real-estate from other bacteria or fungi. I'll still boil all the utensils, regardless.

 The wiki also says B. subtilis is used as a fungicide!