Utilization of a waste glycerol fraction using and reusing immobilized Gluconobacter oxydans   ATCC 621 cell extract

Background: Depletion of petroleum resources has enforced the search for alternative sources of renewable energy. Introduction of biofuels into the market was expected to become a solution to this disadvantageous situation. Attempts to cover fuel demand have, however, caused another severe problem—the waste glycerol generated during biodiesel production at a concentration of approximately 10% w/w. This, in turn, prompted a global search for effective methods of valorization of the waste fraction of glycerol.
Results: Utilization of the waste fraction at 48 h with an initial glycerol concentration of 30 g·L^-1 and proceeding with 62% efficiency enabled the production of 9 g·L^-1 dihydroxyacetone at 50% substrate consumption. The re-use of the immobilized biocatalyst resulted in a similar concentration of dihydroxyacetone (8.7 g·L^-1) in two-fold shorter time, with an efficiency of 85% and lower substrate consumption (35%).
Conclusions: The method proposed in this work is based on the conversion of waste glycerol to dihydroxyacetone in a reaction catalyzed by immobilized Gluconobacter oxydans cell extract with glycerol dehydrogenase activity, and it could be an effective way to convert waste glycerol into a valuable product.

Keywords
Biodiesel; Biofuels; Conversion of waste glycerol; Dihydroxyacetone; Fuel demand; Glycerol dehydrogenase; Glycerol waste fraction valorization; Immobilized cell extract; Renewable energy; Substrate consumption; Utilization