Characterization of a 1,2-Propanediol Producing Escherichia Strain Isolated from a Geothermally Heated Intertidal Pool in Northern Iceland

Abstract

The ability of a mesophilic isolate, strain CC5C, isolated from a temperate geothermally-heated intertidal pool in northern Iceland is described herein. Strain CC5C belongs to the family Enterobacteriaceae with greater than 99.1% similarity to Escherichia marmotae and Shigella dysenteriae based upon 16S rRNA gene analysis. Strain CC5C is a facultative anaerobe exhibiting growth between 5 and 50°C with an optimal growth at 40°C, initial pH values between 4.0 and 9.0 with an optimum at pH 7.5. Strain CC5C, unlike its nearest phylogenetic neighbors, degrades starch, dulcitol, and sucrose as well as potentially cellobiose which are uncommon features among these genera. Under aerobic conditions the catabolism of L-rhamnose and L-fucose revealed that the dominant product was 1,2-propanediol while under anaerobic conditions it was a mixture of acetate and 1,2-propanediol. The effect of increased initial substrate concentration was investigated for glucose, L-fucose, and L-rhamnose with inhibition apparent at concentrations above 20 mM under both anaerobic and aerobic conditions. Although, differences in end product formation were observed between aerobic and anaerobic conditions for L-rhamnose. Strain CC5C rapidly catabolizes rhamnose and produces 1,2-PD at a rate of 3.41 mmol/h on L-rhamnose and 2.37 mmol/h on a mixture of glucose and rhamnose with up to 96% of the theoretical yield on L-rhamnose.