The production of biofuels from renewable energy sources is one of the most important issues in
industrial biotechnology today. The process is known to generate various by-products, for example crude
glycerol, which is obtained in the making of biodiesel from rapeseed oil. Crude glycerol may be utilized in
many ways, including microbial conversion to 1,3-propanediol (1,3-PD), a raw material for the synthesis of
polyesters and polyurethanes.
The paper presents results of a study on the synthesis of 1,3-propanediol from crude glycerol by a
repeated batch method with the use of Clostridium butyricum
DSP1. Three cycles of fermentation medium
replacement were carried out. The final concentration of 1,3-PD was 62 g/L and the maximum productivity,
obtained during the second cycle, reached 1.68 g/L/h. Additionally, experiments conducted in parallel to the
above involved using the entire quantity of the culture broth removed from the bioreactor to inoculate
successive portions of fermentation media containing crude glycerol at concentrations of 80 g/L and 100 g/L.
Under those conditions, the maximum 1,3-PD concentrations were 43.2 g/L and 54.2 g/L.
The experiments proved that by using a portion of metabolically active biomass as inoculum for
another fermentation formula it is possible to eliminate the stage of inoculum growth and thereby reduce the
length of the whole operation. Additionally, that strategy avoids the phase of microbial adaptation to a
different source of carbon such as crude glycerol, which is more difficult to utilize, thus improving the kinetic
parameters of 1,3-PD production.