Patent ID: 8465961

Claim:
An isolated improved xylose-utilizing Zymomonas strain obtained by a method comprising: a) providing xylose-utilizing Zymomonas cells; b) continuously growing the xylose-utilizing Zymomonas cells of (a) in a feeding growth medium comprising xylose, whereby a culture comprising ethanol is produced; c) adding to the culture made in (b) an amount of ammonia and acetic acid or ammonium acetate, whereby a stress culture comprising ethanol and ammonium acetate is produced; d) continuously growing the stress culture made in (c), whereby improved xylose-utilizing Zymomonas cells are produced, wherein the improvement in the cells is increased conversion of xylose to ethanol in the presence of ammonium acetate compared to the Zymomonas cells of (a); e) isolating one or more cells from the improved culture made in (d); and f) growing the one or more improved cells to make the strain.