thank you for your answer.
The product is traditional food like pickle, vegetable yogurt ...
lactic acid fermentation is main process
so pH is roughly 5.5 - 4.0 during shelf life.
The arising time of yeast colony on the surface of product (of course , It
is tightly closed) is the late of shelf life(pH 4.0).
Identification of species is not yet conducted.
Sorry for my bad english.