Biodiesel is an alternative transport fuel which is made from renewable sources such as vegetable oils and animal fats. Recently, biodiesel production has received increasing attention due to national and international legislations, increasing petroleum prices, depletion of conventional fuels and potential environmental benefits of biofuels. As the demand and the production of biodiesel grow fast, the development of methods to increase the sustainability of the biodiesel industry becomes an urgent topic. Thus glycerol, which is the main side product and represents 10% (w/w) of the biodiesel produced [1], should be utilized. The fermentation of glycerol for the production of green chemicals is becoming an attractive option due its cost-effectiveness potential, environmental friendliness [2] and its ability to be dissimilated by a number of bacteria [3].

The aim of this work is to bioconvert, glycerol by the bacterium Actinobacillus Succinogenes to Succinic Acid (which is a platform chemical for the production of various added-value derivatives) for the first time to our knowledge. Glycerol is the only carbon source in our batch fermentation process. The training of Actinobacillus Succinogenes in a glycerol-rich environment in order to increase its effectiveness in consuming glycerol is an important part of the process. Experimental studies are performed and a number of sensitive parameters are identified through a factorial experimental procedure which is designed to examine the influence of these parameters on the Succinic Acid production. A phenomenological unstructured mathematical model that efficiently describes the biological system is constructed, which includes all the important parameters that have been experimentally identified. The model is used to compute optimal operating/parametric conditions which maximise yield, productivity and/or the final Succinic Acid concentration. The main degrees of freedom of the model are CO2 provision, the addition of electron donors, the C/N initial ratio and the O2 availability. The necessary kinetic parameters for the model are estimated experimentally and model predictions are validated with appropriate experimental results.

References

1. Barbirato F, Himmi HE, Conte T and Bories A, 1,3-propanediol production by fermentation: An interesting way to valorize glycerin from the ester and ethanol industries. Ind Crops Prod 7:281-289 (1998)

2. McKinlay JB, Vieille C, Zeikus JG, Prospects for a bio-based succinate industry. Appl Microbiol Biotechnol 76:727-740 (2007)

3. Lin ECC, Glycerol dissimilation and its regulation in bacteria. Annu Rev Microbiol 30:535-578 (1976)