I am searching for a ways to preserve the banana, and most of the time they said that I need to wrap the stems in a plastic or scotch tape so the gas wont come, they said that this gas is the reason why banana ripens fast.  I am thinking that maybe by separating each bananas then cutting the stem of each one of them instead of wrapping them will effectively preserve the bananas? It is very time consuming to wrap each one of the stem.   
From what I understand, ethylene gas is released at the stem. This causes fruit to ripen quicker. That's why you'd want to wrap the stem. If you separate them, you'd still need to wrap each one individually as gas is released there. There might be some additional benefit to separating it as, you can allow each banana to ripen at it's own rate. But if that's too time consuming, just wrap the whole bunch at once will offer some benefit. I can't imagine that taking more than a few seconds?   Cutting the stems, I imagine would only serve to speed that process up.  http://www.instructables.com/id/Keep-Bananas-Fresh-Longer-slices-too/?ALLSTEPS 