Biological conversion of glycerol into value added products

Glycerol is an underutilized byproduct from the chemical processing of biological origin fats and oils. Aspects of the biological conversion of glycerol into value added products were investigated in this dissertation. (1) The first aspect investigated was the nutrients required for the Clostridium butyricum fermentation of glycerol to 1,3 propanediol. The nutrient supply was minimized, and unnecessary and rich components were eliminated. Batch fermentations with this nutrient minimized media resulted in a 90% substrate utilization, converting 51% (w/w) into product, with a maximum specific productivity of 0.2% (w/w) per hour. (2) A packed bed/fluidized bed reactor insert, novel to use in fermentation studies, was also designed that can be used in stirred tank reactors that allowed the study of immobilized biocatalyst performance in the typical stirred tank reactor configuration. Alginate beads were not sufficiently stable to be useful for the C. butyricum fermentation of glycerol, but expanded vermiculite was found to be a suitable immobilization matrix. (3) Enzymatic techniques for the conversion of glycerol were investigated. The extent of the enzymatic conversion of glycerol to 3-hydroxypropionaldehyde was found to be limited by substrate induced enzyme inactivation. Inactivation was not due to enzyme thermal denaturation, coenzyme limitation, or oxidative events. This inactivation event was observed to be due to the time of exposure to the substrate and not due to the number of reactions performed by the enzyme. (4) A naturally solvent tolerant bacteria, Providencia rettgeri OF011, was shown to be genetically modified using Escherichia coli techniques and materials. This solvent tolerant organism could prove useful for increased solvent concentration in fermentations, or for solvent/solvent extractions of fermentations. The technique that currently shows the most promise for converting glycerol into a value added product, in an industrially relevant manner, is the fermentation route to 1,3 propanediol