Re: Unlikely
Perhaps I was not clear in my post... most B12 production has focused on the "bacterial" production and absorption... pancreatic enzymes among others being necessary too... a weak link in the chain and we have a problem with production and/or absorption, and may likely need to supplement.
In fact levels of B12 absorption have been shown to fall with impaired pancreatic function and removal of all or a part of the ileum, etc. etc.
My guess is that any one of us modern humans have probably fallen in our ability to make and/or absorb nutrients for one of many reasons or another.
B12 has been found to be produced by gram negative and positive bacteria, both rod and cocci forms, yeasts and molds.
This product,
http://www.scdworld.net/ProductDetails.asp?ProductCode=A112%2D1&Show=ExtInfo
with Saccharomyces cerevisiae may be worth a go... one liter can be extended to 22 liters or so using your own BSM to cultivate; it is very cost effective.
Just like healthy bacteria... there are good and healthy levels of yeasts occupying our gut, contributing to our nutritional needs too...
grz-