Production of 1,3-propanediol in EGSB reactors by open mixed cultures using glycerol as the carbon source

Abstract

Two pre-treatments (granules disruption and heat) were applied to granular sludge to favour the production of 1,3-propanediol (1,3-PDO) from glycerol by non-methanogenic bacteria in expanded granular sludge blanket (EGSB) reactors. Different hydraulic retention times (HRT) were tested to achieve a maximum yield of 0.59 mol of 1,3-PDO/mol of glycerol in the control (no treatment) reactor at an HRT of 12 h. Molecular biology tools were used to evaluate the microbial community present in the inoculum and biomass for each HRT studied. Variations in the HRT had a critical impact in the dominant community of microorganisms. No appreciable differences in microbial population were observed between the reactors operated with heat–treated and disrupted granules at low HRTs. Additionally, the production of H2 was observed at the beginning of the operation, however this was associated with low production of 1,3-PDO. In turn, no methane production was observed. This study proves the feasibility of 1,3-PDO production in EGSB reactors, which have the advantage of being operated under non-sterile conditions and represent a novel strategy to valorise glycerol being generated as by-product in the biodiesel industry.