Formation of higher alcohols and phenol by strains of zymomonas sp.

Abstract

AbstractStrains of the bacteria Zymomonas sp. were studied for their ability to form higher alcohols. In a complex growth medium, six strains were shown to produce significant amounts of 1‐propanol, 1‐butanol, 2‐methyl‐1‐butanol, 3‐methyl‐1‐butanol, 2‐methyl‐2‐butanol, pentanols, secondary hexyl‐alcohols, and trace amounts of n‐hexanol. When resting cells of these organisms were placed into a fermentation medium containing glucose and Tris‐buffer, Z. mobilis 8938 produced increased levels of 1‐butanol, and secondary hexyl‐alcohols at concentrations of 13.5 mg/liter and 5.8 mg/liter, respectively. Another strain, Z. mobilis subsp. mobilis B 806, stimulated the formation of 1‐propanol and 1‐butanol at concentrations of 14.9 mg/liter and 23.52 mg/liter, respectively. Amino acids or amino acid precursors were then added to the fermentation medium. The presence of threonine and α‐ketobutyric acid stimulated Z. mobilis 8938 to produce 82.6 mg/liter secondary hexyl‐alcohols and 8.0 mg/liter n‐hexanol, respectively. Isoleucine and valine increased the production of 2‐methyl‐1‐butanol (394.0 mg/liter) and 3‐methyl‐1‐butanol (113.4 mg/liter), respectively, by Z. mobilis subsp. mobilis B 806. Glutamine enhanced the formation of 2‐methyl‐2‐butanol production to concentrations 38.8 mg/liter in Zymomonas strain B 806. Additional experiments suggested that higher alcohol production could also be accomplished in the absence of glucose when cells were allowed to metabolize the precursors only. The effect of aromatic amino acids on phenol production was determined using resting cells of Zymomonas sp. The maximum yield of phenol (111.6 mg/liter) was found by Zymomonas strain 8938 in the presence of tyrosine. The addition of phenylalanine also stimulated this strain to form 71.4 mg/liter of phenol.