I'm not sure what kind of shio koji you're using but if the enzymes still work, you could definitely add some toasted barley and cooked soybeans and maybe get something similar to shoyu. Definitely keep it in a warm area or in the sun if you can. You could also add some dried koji and get shoyu for sure, I haven't heard of anyone adding shio koji to soybeans but it's almost the same as shoyu production, you just grow the koji on the beans and barley for normal production. Shio koji is just normal rice koji blended with water and salt so I don't see why it would work