Living microbial cells are considered to be the catalyst of choice for selective terpene functionalization. However, such processes often suffer from side product formation and poor substrate mass transfer into cells. For the hydroxylation of (S)-limonene to (S)-perillyl alcohol by Pseudomonas putida KT2440 (pGEc47ΔB)(pCom8-PFR1500), containing the cytochrome P450 monooxygenase CYP153A6, the side products perillyl aldehyde and perillic acid constituted up to 26% of the total amount of oxidized terpenes. In this study, it is shown that the reaction rate is substrate-limited in the two-liquid phase system used and that host intrinsic dehydrogenases and not CYP153A6 are responsible for the formation of the undesired side products. In contrast to P. putida KT2440, E. coli W3110 was found to catalyze perillyl aldehyde reduction to the alcohol and no oxidation to the acid. Furthermore, E. coli W3110 harboring CYP153A6 showed high limonene hydroxylation activities (7.1 U g CDW-1). The outer membrane protein AlkL was found to enhance hydroxylation activities of E. coli twofold in aqueous single-phase and fivefold in two-liquid phase biotransformations. In the latter system, E. coli harboring CYP153A6 and AlkL produced up to 39.2 mmol (S)-perillyl alcohol L tot-1 within 26 h, whereas no perillic acid and minor amounts of perillyl aldehyde (8% of the total products) were formed. In conclusion, undesired perillyl alcohol oxidation was reduced by choosing E. coli's enzymatic background as a reaction environment and co-expression of the alkL gene in E. coli represents a promising strategy to enhance terpene bioconversion rates.

This work presents a modeling approach using the Perturbed Chain-Statistical Associating Fluid Theory (PC-SAFT) for new liquid−liquid equilibria (LLE) data of ternary systems containing β-myrcene, acetonitrile, and n-alkanes, as well as binary mixtures thereof. The modeling approach is based on parameter estimations from binary systems and allows a general prediction of acetonitrile/n-alkane systems' LLE and their ternary mixtures' LLE with β-myrcene. The binary mixtures' vapor− liquid equilibria (VLE) of β-myrcene with acetonitrile and n-alkanes were measured at 100 mbar. The ternary systems' LLE were measured at ambient pressure and 298.15 K. Experimentally investigated alkanes are n-hexane, n-heptane, and n-octane. The approach was validated by successfully predicting the ternary system containing n-dodecane. ■ INTRODUCTIONDue to the natural limitation of fossil feedstock, terpenes (such as, e.g., myrcene) have gained significant interest in the chemical industry as renewable resources. 1 Terpenes are the main components of several resins (e.g., conifers). As conifers are perennial, modest plants, farming and exploiting is possible over several years. Because of a lack of a competition to food production, terpenes are a superior starting material compared to sugar or fatty acids. Among the terpenes, β-myrcene (myrcene, Figure 1)due to its unsaturated isoprene unitis an attractive starting substance for several reaction pathways. 2 This work focuses on homogeneously catalyzed hydroamination which is fast and selective. An atom-economic conversion of myrcene provides a sustainable way to alkyl amines on the basis of renewable feedstock. As catalysts are cost intensive, a recycling and reuse of the catalyst is preferable for an economic process design.A possible strategy to achieve catalyst recycling in homogeneous catalysis is the use of thermomorphic multicomponent solvent systems (TMS), 2b which show a temperature-dependent miscibility gap. At reaction temperature, the mixture is homogeneous. This ensures a fast bulk reaction. By cooling down to separation temperature, two liquid phases are formed. Ideally, one phase carries the catalyst, whereas the product enriches in the other one. Thereby, catalyst recycling and product removal can be achieved in one step by extraction. One promising TMS for the hydroamination of myrcene is a mixture of acetonitrile with an n-alkane, whereas the catalyst (palladium with 1,4-bis(diphenylphosphino)butane as ligand) enriches in the acetonitrile-rich phase and the alkyl amine enriches in the alkane-rich phase. Until now the homogeneouscatalyzed hydroamination has been carried out with n-heptane as one TMS component. 2b It was however shown that the catalyst leaching corresponds to the concentration of the polar compound, here acetonitrile, in the apolar alkane-rich phase. 3 As the miscibility gap of TMS composed of acetonitrile and nalkanes broadens with increasing chain length of the applied alkane, a thermodynamic modeling of the phase behavior as a function of alkane chai...

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Solvents are known to have strong impacts on the yields of equilibrium reactions. This work focuses on the thermodynamic investigation of these solvent effects on esterification reactions of acetic acid and propionic acid with ethanol. Esterification of acetic acid was performed in the solvents acetone, acetonitrile (ACN), dimethylformamide (DMF), and tetrahydrofurane as well as in mixtures thereof. ACN promotes the esterification of acetic acid, whereas it is strongly suppressed by DMF. The esterification of propionic acid was investigated with various reactant concentrations in acetone. The experimental equilibrium data in pure solvents and solvent mixtures were modeled using the thermodynamic equilibrium constant Ka and the reactant/product activity coefficients predicted by the perturbed chain‐statistical associating fluid theory (PC‐SAFT). For a given Ka, PC‐SAFT is able to predict the influence of the solvent and even solvent mixtures on the equilibrium concentrations of esterification in almost quantitative agreement with the experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3000–3011, 2015