Synergy at work: linking the metabolism of two lactic acid bacteria to achieve superior production of 2-butanol

Abstract

Background: The secondary alcohol 2-butanol has many important applications, e.g., as a solvent. Industrially, it is usually made by sulfuric acid-catalyzed hydration of butenes. Microbial production of 2-butanol has also been attempted, however, with little success as witnessed by the low titers and yields reported. Two important reasons for this, are the growth-hampering effect of 2-butanol on microorganisms, and challenges associated with one of the key enzymes involved in its production, namely diol dehydratase. Results:We attempt to link the metabolism of an engineered Lactococcus lactis strain, which possesses all enzyme activities required for fermentative production of 2-butanol from glucose, except for diol dehydratase, which acts on meso-2,3-butanediol (mBDO), with that of a Lactobacillus brevis strain which expresses a functional dehydratase natively. We demonstrate growth-coupled production of 2-butanol by the engineered L. lactis strain, when cocultured with L. brevis. After fine-tuning the co-culture setup, a titer of 80 mM (5.9 g/L) 2-butanol, with a high yield of 0.58 mol/mol is achieved. Conclusions:Here, we demonstrate that it is possible to link the metabolism of two bacteria to achieve redoxbalanced production of 2-butanol. Using a simple co-cultivation setup, we achieved the highest titer and yield from glucose in a single fermentation step ever reported. The data highlight the potential that lies in harnessing microbial synergies for producing valuable compounds.

Low-temperature selective ethanol upgrading to primary or secondary alcohols by homogeneous catalysis

“…The industrial production of 2-butanol exceeds 800,000 tons per year 14 , and is manufactured from glucose by fermentation 15,16 . 2-butanol is widely used as a pharmaceutical standard 17 , solvent 18 , and fuel additive 19 .…”

Tuning Ethanol Upgrading toward Primary or Secondary Alcohols by Homogeneous Catalysis

“…The industrial production of 2-butanol exceeds 800,000 tons per year and is manufactured from glucose by fermentation. , 2-Butanol is widely used as a pharmaceutical standard, a solvent, and a fuel additive . Among these applications, it is a crucial intermediate in the chemical production of 1-butene, 2-butene, butyl acetate, , sec -butyl acetate, and methyl ethyl ketone .…”

“…To the best of our knowledge, there are no reports on ethanol upgrading to 2-butanol or hydrocarbons under mild catalytic conditions (Figure 1, lower pathway). The industrial production of 2-butanol exceeds 800,000 tons per year 14 and is manufactured from glucose by fermentation. 15,16 2-Butanol is widely used as a pharmaceutical standard, 17 a solvent, 18 and a fuel additive.…”