2,3-Butanediol
(2,3-BD), especially when it exists in the chirally
pure form, is a valuable chemical feedstock with numerous applications
in various industries. However, in most cases, the 2,3-BD naturally
produced by the microorganism is a mixture of two of the three isomers
(d-2,3-BD, l-2,3-BD, and meso-2,3-BD),
which has restricted applications and thus a much lower value than
the chirally pure one. In this study, we report a new isolate Bacillus spp. FJ-4 strain, which can produce highly chirally
pure d-2,3-BD (>99.9%) to high levels, with very high
productivity
and yield. The composition of the fermentation medium for the strain
was sequentially optimized using statistical experimental methodologies.
During a fed-batch experiment, 100.0 g/L of d-2,3-BD was
produced from 226.8 g/L glucose, with a yield of 0.44 g/g (88.2% of
the theoretical maximum). Acetoin was the primary byproduct, and no
other byproduct such as lactate, acetate, or ethanol was detected,
which would be advantageous for the downstream purification process.
Moreover, no special conditions such as limited oxygen level (which
generally limits the cell growth and thus final d-2,3-BD
production) are required for the fermentation. These results indicated
that Bacillus spp. FJ-4 is a robust workhorse for
efficient d-2,3-BD production from low-value carbon sources.