Which gas makes Orange juice bottles swell?

I forgot a bottle of 1L Orange Juice (100% orange juice with pulp) in the fridge for about a week, the bottle was previously open so air got inside as well.


After a week the bottle got inflated and when I opened it I could hear the gas coming out. No odours, orange juice still the same colour (not sure if the same taste, I threw it away).


Which gas was produced and how did it happen? The air that got in seems to have played a part on it (these bottles stay in the supermarket closed for a long time without getting inflated).




I can't imagine the gas was anything except $\ce{CO2}$ formed by the action of microorganisms contaminating the orange juice. They degrade the organic components of the juice to power their metabolisms, and produce carbon dioxide as a byproduct. 


A common contaminant of pasteurized fruit juice is a genus of bacteria called *Alicyclobacillus*, but [this paper](http://onlinelibrary.wiley.com/doi/10.1111/j.1472-765X.2007.02229.x/abstract) says that *Alicyclobacillus* bacteria do *not* cause bottle swelling and *do* cause a medicinal smell.


By searching Google for ["bottle swelling" "orange juice"], I found an English-language abstract of a [thesis](http://www.dissertationtopic.net/doc/1719787) from China which implies that the culprit could be a yeast.


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