Biotransformation of glycerol into 1,3-propanediol

Today, glycerol is mainly a by-product of fat splitting and biodiesel production. Further growth of the biodiesel market would result in a fall in the price of glycerol. Particularly glycerol-water from rapeseed oil methyl ester production, for example, would be an interesting raw material if it could be utilised in fermentation without further pretreatment. Under anaerobic conditions, bacteria can transform glycerol into 1,3-propanediol (PDO), which can be used as a monomer in the chemical industry. PDO can be produced biotechnologically from glycerol with the aid of bacteria. Another way would be the utilization of glucose instead of glycerol, which would provide independence from the fluctuating glycerol market. However, under certain conditions, the classic technique based on glycerol can be quite interesting with regard to technical and economic aspects: A concerted, extensive search for new microorganisms (screening) and improved process design (fed-batch with pH-controlled substrate dosage) allowed the product concentrations, which were relatively low at a maximum of 70-80 g/L as a result of product inhibition, to be raised to more than 100 g/L. An additional advantage of the new technique and the newly isolated strains is the utilisation of low-priced crude glycerol or glycerol-water. This is a factor which should not be underestimated and has a direct effect on the product costs. Further on, the use of immobilised cells compared to freely suspended cells enables an increase of productivity from about 2 up to 30 g /Lh.