P31: Optimization of bacterial 3-hydroxypropionaldehyde production on raw glycerol

The commercially valuable specialty chemical 3-hydroxypropionaldehyde is utilized in the production of plastics. Using a mutant strain of Citrobacter freundii ATCC 8090 capable of elevated 3-hydroxypropionaldehyde production, optimization of aldehyde production on raw glycerol was achieved by varying the concentration of semicarbazide hydrochloride present in a buffered medium. Semicarbazide hydrochloride blocks the action of a reductase in the bacterium which degrades 3-hydroxypropionaldehyde into 1,3-propanediol. The mutant strain was grown in a complex medium containing soy biodiesel-based raw glycerol (1% or 6%) for 24 hours at 28^oC. The cells were collected by centrifugation and resuspended in a neutral phosphate buffer containing the same concentration of raw glycerol and a selected concentration of semicarbazide hydrochloride. The cell suspensions were shaken for 24 hours at 28^oC and then the cells were collected by centrifugation. Using a spectrophotometric assay for 3-hydroxypropionaldehyde, the aldehyde level in the supernatant of each suspension was measured. It was found that the highest 3-hydroxypropionaldehyde concentration was produced by the mutant strain on raw glycerol when a concentration of 0.75% semicarbazide hydrochloride was present in the buffer. In summary, it was possible to optimize 3-hydroxypropionaldehyde production by C. freundii on soy biodiesel-based raw glycerol by identifying the most effective semicarbazide hydrochloride concentration that inhibited aldehyde degradation.