It's not certain either are bidders for BioAmber although BioAmber mentions Cargill as a partner (patents) and ADM is (if i'm not wrong) Cargill's largest rival. To both companies this Sarnia plant is quite an addition to their succinic acid production. ADM has been mentioned not only as a competitor but there are flight records of Learjet leaving Chicago (ADM HQ) going to Sarnia and returning, with the assumption of how many private jets take that flight path it is quite an indication of ADM being a potential bidder.
Again I could be completely wrong and this could all be coincidental, although it looks to me like, at least ADM, there is reason to believe these two Co.'s are the major bidders.