The effect of immobilization on rhamnolipid production by Pseudomonas fluorescens

Pseudomonas fluorescens in free suspension and immobilized to a commercially available biosupport (Biofix) and a biosorbent (Drizit), were used as bioremediation agents in an aqueous system with petrol (Slovene diesel) as the carbon source. Analysis of cellular growth and estimation of rhamnolipid production was carried out on the free suspension of the free and immobilized systems over 5 d. An increase in growth and rhamnolipid production was seen in the immobilized systems in comparison to the free system. EDTA was shown to be an inhibitor of rhamnolipid production. Its addition to the aqueous suspensions of all systems resulted in a fall in production of the surface-active agent in all cases, with no corresponding decrease in growth. This indicates the bacteria can rely on contact between the cell and the oil droplet for hydrocarbon transport into the cell. The data from this study indicated that immobilization resulted in a combination of increased contact between cell and hydrocarbon droplets and enhanced levels of rhamnolipid production.