Yield and kinetic constants estimation in the production of hydroxy fatty acids from oleic acid in a bioreactor by Pseudomonas aeruginosa 42A2.

We modelled the production of hydroxy fatty acids from oleic acid by Pseudomonas aeruginosa 42A2 in a bioreactor with a non-dispersive aeration system. First, we designed an adapted wetted-wall gas-absorption column, offering a k La value of 39.9 h(-1), to enhance oxygen absorption in the culture media and prevent foam formation. Then, we analysed different kinetic models to simulate the yield coefficients and the kinetic constants in this bacterial transformation. Monod model fitting (µ max1 = 0.51 h(-1), K S1 = 1.60 C-mol l(-1), µ max2 = 0.12 h(-1), K S2 = 0.035 C-mol l(-1), and k 2 = 0.033 h(-1)) showed a good accuracy with the experimental data sets and was chosen for its simplicity. Lastly, mass balances were carried out to establish the stoichiometry of this biotransformation with the following yield coefficients, Υ X/OA, Υ X/(10S)-HPOME and Υ (10S)-HPOME/(7S10S)-HPOME of 0.172, 0.347 and 2.388 C-mol C-mol(-1), respectively.

Production of 10(S)-hydroxy-8(E)-octadecenoic and 7,10(S,S)-hydroxy-8(E)-octadecenoic ethyl esters by Novozym 435 in solvent-free media.

Novozym 435, lipase B from Candida antarctica, was used in this study for the production of ethyl esters. For the first time, trans-hydroxy-fatty acid ethyl esters were synthesized in vitro in solvent-free media. We studied the effects of the substrate-ethanol molar ratio and enzyme synthetic stability of the biocatalyst. To determine the structure of the formed compounds, Fourier transformed infrared spectroscopy, nuclear magnetic resonance, and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry were used, three less time-consuming structural techniques. trans-Hydroxy-fatty acid ethyl esters were synthesized with a reaction yield of 90 % or higher with optimal reaction conditions.

Hydroxy-fatty acid production in a Pseudomonas aeruginosa 42A2 PHA synthase mutant generated by directed mutagenesis.

Pseudomonas aeruginosa 42A2 growing on waste frying oils is capable to synthesize polyhydroxyalkanoic acids (PHAs) and hydroxy-fatty acids as a result of several enzymatic conversions. In order to study the physiological role of PHA biosynthesis in P. aeruginosa with respect to the synthesis of hydroxy-fatty acids, an unmarked deletion mutant deficient for PHA biosynthesis was generated in P. aeruginosa 42A2. A combination of the sacB-based negative selection system with a cre-lox antibiotic marker recycling method was used for mutant isolation. Electron microscopy, nuclear magnetic resonance analysis, and transmission electron microscopy confirmed that PHA accumulation was completely abolished in the mutant strain. Interestingly, the new mutant strain showed higher carbon and oxygen uptake rate than the wild-type strain and higher efficiency in the conversion of oleic acid into (E)-10-hydroxy-8-octadecenic acid-octadecenoic acid.