Pseudomonas extremaustralis produces different surfactants compounds when growing in diesel as sole carbon source.

MAYRA F. CASTAÑEDA; LAURA J. RAIGER LUSTMAN; RUBY TERRANOVA

Virtual

Congreso; SAIB-SAMIGE 2020; 2020

SAIB-SAMIGE

Pseudomonas extremaustralis is an environmental bacterial isolated from Antarctica. During the last decades it was studied in our lab as a model of stress resistance. As part of this study, this strain was also analyzed for its capability to grow in diesel as sole carbon source even though it was isolated from a pristine environment. Previous reports showed that P. extremaustralis was able to grow with diesel as sole carbon source only when cultures were carried on in microaerobiosis (biofilms or microaerobic planktonic growth). The aim of this work was to analyze the biosurfactants synthetized by P. extremaustralis and a recombinant strain carrying a plasmid pGEc47 (P. extremeustralis / pGEc47) to study the chemical nature of these compound and to compare the ones synthetized by the recombinant strain when was cultured under microaerobic or aerobic condition. The pGEc47 plasmid encodes the alk genes of P. putida GPo1 and allows the use of medium chain alkanes due to the heterologous expression of these genes, and in the case of P. extremaustralis / pGEc47 also of aerobic growth. To analyze the biosurfactants production, the cultures were performed in E2 minimal medium supplemented with diesel 2% V/V and 0.008% KNO W/V at 28 ° C for 7 days. Microaerobiosis condition were achieved by culturing 500 ml capped bottles with a 300 ml culture without shaking, and aerobic condition was reached by culturing 500 ml flasks with 100 ml of culture at 180 rpm. After incubation time, cultures were centrifuged, and the free cell supernatant was filtered to remove cellular debris. These supernatants were then acidified to pH 2 and allowed to stand at 4°C ON, to be then centrifuged in order to collect the surfactant-enriched fraction. The pellets were resuspended in 1 ml of Tris HCl pH 8 and the surfactants were partitioned in ethyl acetate at least 3 times. The organic phase was collected and concentrated using a rotary evaporator to constitute a crude biosurfactant extract. To analyze the composition of these crude extracts, a TCL analysis was carried out. We observed that both strains produced compounds with peptide and/or glycosidic residues and slight differences were observed between both strains and growth conditions according to the RF obtained in the TLC analysis. Due that the only difference in P. extremaustralis and P. extremaustralis/ pGEc47 are the alk genes and none of them were described as related with surfactant production, these results form the basis for further investigation of the nature of the surfactants produced by this strain