A Greener Solution for Darker Side of Biodiesel: Utilization of Crude Glycerol in 1,3-Propanediol Production

In contrast to the debate on nuclear power and genetically altered food, the public doesn't yet view the manufacturing strategies of biodiesel as a noteworthy hazard. For every 100 gallons of biodiesel produced, 5–10 gallons of the less glamorous crude glycerol are left behind with a sparking debate about the best uses of this waste. This impure form of glycerol must either be disposed off or sold off to market for a minimal amount due to the free fatty acids, water, methanol, and salt content. At present, most of it is simply incinerated. Well that doesn't make biodiesel a clean alternative energy anymore. The utilization of a crude glycerol to produce value–added products provides areas of opportunity where it would be possible to capitalize on the surplus of waste glycerol. In this context, glycerol which promises to be a good substrate for microbial production of 1,3-propanediol, changes the perception of glycerol as being an industrial waste. The present work necessitates to evaluate the possibility of capitalizing on the surplus glycerol by converting it into 1,3-propanediol. In this respect, more then 200 bacterial strains were screened out, to identify their ability to convert glycerol to 1,3-propanediol anaerobically. One of the potent strain which produces 1,3-propanediol was identified as Citrobacter freundii. Various raw and pretreated glycerol types were obtained from biodiesel production processes, used as a substrate to produce 1,3-propanediol in batch fermentation. Production and growth inhibition of C. freundii using different grades of glycerol were evaluated. In order to optimize the production, parametric optimization was carried out to fetch out the best parametric combination. Further, the process was scaled up to 30 L fermentor in which the final yield of 1,3-propanediol reached to maximum of 28.0g/l under anaerobic condition.