Isolation and Characterisation of Halotolerant Bacteria and Algae and their Potential for Biofuel Production

The first aim of the project was to isolate, identify and characterize salt tolerant bacteria from river and pond water. This aim was achieved by the isolation of the salt tolerant bacterium Enterococcus amnigenus from water samples taken from Weston Park pond and by the isolation of the salt tolerant bacterium Pseudomonas fluorescens from a dew pond in the Derbyshire Peak District. E. amnigenus in common with many enterococci, is a potential pathogen, but it also has uses in industry as a producer of bacterial cellulose. P. fluorescens is a ubiquitous organism found in marine and soil environments and has been well characterized as an important biofilm-forming organism and as a rhizobacterium.
The second aim of the project was to isolate salt-tolerant microalgae from the fresh water Weston Park pond and this was successfully achieved by isolating and identifying two algal species - the diatom Navicula pelliculosa and the green alga Chlorella sp. Initial work measuring total lipid concentrations suggested that Navicula was the most promising organism for biofuel production due to having a total lipid concentration of around 20%. Further characterization of Navicula was undertaken to investigate its suitability for biofuel production. It was shown to grow under conditions of high pH and high salinity, making it a candidate species for growth in outdoor raceway ponds. Experiments using Nile Red fluorescence to measure neutral lipid production indicated that stress conditions (high salinity or high pH) could increase the neutral lipid accumulation by Navicula cells. To grow in high salinity (up to 0.8 M NaCl), Navicula cells must balance the external osmotic potential by accumulating a compatible solute within the cells. NMR analysis showed that the compatible solute accumulated by Navicula is glucosylglycerol, which is not normally found in diatoms.