Patent ID: 7767431

Claim:
An isolated E. coli strain which is resistant to threonine raffinate comprising from 0.05% to 5% ammonium sulfate, wherein said threonine raffinate is the waste stream product generated from ion exchange operations for threonine recovery from fermentation broth; which produces between about 95 and about 150 g/L of L-threonine by about 48 hours of growth in culture; and which comprises a chromosome comprising at least one E. coli L-threonine operon obtained from strain ATTC Deposit No. 21277 operably linked to a non-native promoter, and wherein the threonine operon encodes a feedback-resistant aspartate kinase I-homoserine dehydrogenase I (thrA), a homoserine kinase (thrB), and a threonine synthase (thrC).