If Patterson believes that oxygen is removed by the enzyme and only N2 is
produced. What happens to the oxygen? Where do you/he think it goes?
Do you think it stays in the enzyme?

Not enzyme. Bacteria. Yes, that's exactly what happens. The oxygen is
consumed by the bacteria.

First:
These denitrifying bacteria are anaerobic. They thrive in LOW oxygen
conditions. Anoxic conditions are required for their survival. This means
they do not need nor do they consume oxygen to survive. Why do you insist
that anaerobic bacteria involved in denitrification consume oxygen? Oxygen
is a TOXIN for most anaerobic bacteria. They do not produce nor consume
oxygen. Anaerobic bacteria can not even grow in the presence of oxygen.

Second:
Oxygen is NOT produced. The end result biproducts of nitrate metabolism by
denitrifying bacteria are N2 and H2O.

I am not guessing here.

nitrogen cycle:
http://www.reefscapes.net/articles/a...ogencycle.html
http://en.wikipedia.org/wiki/Denitrification