Harnessing glycerol from biodiesel fuel production to obtain valuable industrial compounds

Abstract

Glycerol (Gro) has many appliances in the cosmetic, food, and pharmaceutical industries. However, Gro has become an inexpensive carbon source due to its generation as inevitable by-product of the biodiesel production, a process with outstanding growing within the last decade. In addition, the excess of Gro has environmental problems since it is not innocuous and its disposal turns complex. Thus, conversion of low-priced Gro streams to higher value products, such as 1,3-propanediol or dihydroxyacetone (DHA), has been proposed as relevant biorefinery strategies. Many organisms are able to metabolize Gro, and their enzymes are key targets in the bioconversion of this compound. In this work we have cloned and expressed the gene encoding for Gro dehydrogenase (GroDHase) in Escherichia coli. The enzyme converts Gro into DHA. The recombinant enzyme was purified to near homogeneity either by IMAC or heat-shock treatment. We have analyzed the activity assay conditions and determined the S0.5 values for both substrates, NAD+ (0,5 mM) and Gro (100 mM). The maximum activity was reached at pH 11.0 and 40 ºC. NH4Cl was found to be an activator of GroDHase, reducing (4-fold) the S0.5 for Gro and increasing (1.5-fold) the Vmax. Gro waste derived from biodiesel production was an effective substrate for the enzyme, which supports the biotechnological application of the recombinant GroDHase.