"Production of rhamnolipids by Pseudomonas aeruginosa P029-GVIIA using glucose as substrate and applications"
Biosurfactants, rhamnolipid, bioremediation, antimicrobial activity.
Biosurfactants are amphiphilic compounds of microbial origin, which have aroused as an alternative to the use of chemical surfactants once its use is very aggressive to the environment. On the other hand, biological surfactants have properties similar to the chemical surfactants and also have some advantages over them such as biodegradability, stability in different pH, temperature and salinity conditions, and low toxicity. In face of this situation, several studies have been developed in order to make the production of biosurfactants viable for commercialization. The most researches aims to analyze the production of these compounds using different renewable sources and investigate their surfactant properties. The rhamnolipids, that are biosurfactants produced by bacteria and belonging to the group of glycolipids, are applied in several industrial areas due to its various properties as emulsifying, solubilizing, wetting, so on. Thus, this work aims to verify the production of rhamnolipid by Pseudomonas aeruginosa P029-GVIIA, changing the following parameters: the concentration of glucose (10, 18 and 26 g / L) and the inoculum percentage (3, 10 and 17%) for 72 hours. Along this time the cell growth (X), the glucose concentration consumed (S), the produced rhamnolipid (P), the pH of the system and the production of total proteins were assessed. Five trials were performed and the best condition (26 g / L glucose and 3 ml inoculum) produced 0.838 ± 0.064 g/ L ramnolipid in 24 hours, biomass conversion factor in product (YP/X) of 0.260 g/g, substrate conversion factor in product (YP/S) of 0.034 g/g and product productivity (PP) of 0.021 g/L∙h. At this assay, the biomass reached the highest value among all cultures (2.5 ± 0.041 g/L), pH ranged from 5.8 to 8 and substrate consumption reached 82.45% at the end of the experiment. From the best outcome, there were studied the emulsification index and the emulsifying activity with six different solvents: kerosene, hexadecane, toluene, soybean oil, corn oil and motor oil. The last one presented the best responses with emulsification index of 77.55% in the first 24 hours and high emulsifying stability, 2.23 U. Then, the efficiency of the biosurfactant in the removal of oil present in sand was evaluated in 16.8% and the antimicrobial activity of the ramnolipid against different bacterial and fungal species were determined, showing its ability to inhibit fungi of the species Candida tropicalis and Candida albicans. In this way, the results obtained prove the potential of the rhamnolipid produced for biotechnological applications.