PRODUCTION OF RHAMNOLIPIDS IN DIFFERENT FERMENTATIVE PROCESSES BY Pseudomonas Aeruginosa PAO1

Rhamnolipids produced by Pseudomonas aeruginosa are an important class of microbial biosurfactants (surfactants produced by microorganisms), which have attracted attention because of their low toxicity, biodegradability and ecological acceptability. Among of wide variety of application, those where it is necessary the dispersion of surfactants in the environment, specifically in the cleaning of oil spills and hydrophobic compounds and in the increase of oil recovery of reservoirs are the most important for use of ecofriendly product such as rhamnolipids. Another advantage of rhamnolipids is that they can be produced from low-cost materials such as carbohydrates, vegetable oils, or even effluent from food industries. However, the use of these compounds is currently extremely limited due to their high cost of production, compared to surfactants of chemical origin. The utilizations of solid-state substrates in submerged cultivation represents an alternative technology for biosurfactant production that can avoid the problem of foaming, which complicates submerged cultivation processes for biosurfactant production, without increase the production costs. The present work aims to study production of a Pseudomonas aeruginosa glycolipid-surfactant by different cultivation in the presence and absence of solid-state support/substrate. Three types of cultivation [submerged (CSb), static submerged (CSbE) and submerged with solid support (CSb-SS)] were evaluated. Solid supports used were cheesecloth, cotton, glass wool and corn bran. The experiments were conducted in 125 ml Erlenmeyer flasks, incubated at 37°C for 216 hours. The surfactant of interest was extracted with organic solvent (CHCl3:CH3OH 3:1) and then indirectly quantified by the phenol-sulfuric method. In the cultivation using inert matrix the best condition was reached using cheesecloth as solid support (4 g/L). In the evaluation of the rotation/aeration speed, better results were reached with 200 rpm. A significative improvement on the rhamnolipids yield was reached when corn bran was used as solid-state substrate in submerged cultivations. An additional concentration of glycerol used in the cultivation with presence of corn bran promoted an improvement in rhamnolipids production reaching close to 20 g/L. The present results suggest that the presence of a solid matrix in the submerged cultivation is an interesting alternative to produce rhamnolipids by P. aeruginosa increasing yields and avoiding foam formation.