Abstract

Rhamonolipids (RHL) and medium-chain-length polyhydroxyalkanoates (PHAMCL) are produced simultaneously by several Pseudomonas species in the stationary phase of growth. Both compounds have 3HAMCL as constituent and it is expected at least some related regulatory features. The simultaneous production of these compounds is interesting since one can be recovered from cell biomass and the other from supernatant. Therefore, the same process could be used to produce both compounds reducing the impact of capital investments in their final prices. On the other hand, a better knowledge of the biosynthesis regulatory network of PHA and RHL could be used to generate bacterial strains specialists in the synthesis of one of these compounds. Pseudomonas sp. LFM634 was selected as a RHL producer since presented a good performance in the production of RHL. A library of mutants was obtained using the mini-Tn5 transposon. Mutants presenting performance affected in the production of RHL were selected based on qualitative analysis in blue-agar plates. Mutants producing amounts of RHL higher as well as lower than the wild type strain were selected. Some of the genes interrupted by mini-Tn5 in the mutants encode for: transcriptional regulators, histidine kinase sensors, O-antigen biosynthesis proteins and ABC transporters. The mutant LFM1153 presented increase of about 15-20% in the production of RHL using glucose as the only carbon source, but no increase/decrease in PHA production was detected. Using soybean oil as the only carbon source, the mutant LFM1205 showed an increase of 50-60% and 90% in the production of RHL and PHA, respectively. The increase of the amounts of rhamnose and 3HAA produced were similar, suggesting that the genetic modification improve the synthesis of RHL as a whole. The performance of other mutants will be evaluated to establish the relationship between gene affected and changes in the production of PHA and/or RHL.