Production of trehalose from a cellulosic-derived building-block, levulinic acid, by Burkholderia stabilis

Recently, much attention has been paid to biorefineries, which enable the production of biofuels as well as building-block chemicals from biomass. Of the diverse chemicals other than sugars that can be synthesized from cellulose, levulinic acid (LA) is a promising building block for chemical production; indeed, it is considered one of the top 12 building blocks by the US Department of Energy. To investigate the potential of LA as a substrate for microbial conversion to chemicals, we isolated and identified LA-utilizing bacteria. Among the six isolated strains, Burkholderia stabilis LA20W, produced trehalose extracellularly in the presence of 40 g/L LA to approximately 2 g/L. Identification of trehalose in the medium was as follows: After removal of cells by centrifugation and any remaining sodium levulinate using anion-exchange resin, the molecular mass of the unknown metabolite were determined by LC-MS to be 342 g/mol, which suggested it to be a disaccharide. TLC analysis revealed that it was anthrone positive and that the R_f value corresponded to that of trehalose. To confirm the result, GC-MS analysis was performed after derivatization of the sample with MSTFA; the mass spectrum of this compound exhibited major fragment ions at m/z 361, 271, 191, 147, and 73, with a retention time (RT) of 74.8 min. The molecular mass and fragmentation patterns of the compound were identical to those of authentic trehalose.