In situ phenol pertraction with 1-octanol has been experimentally studied to improve the production of the model component phenol by a recombinant strain of Pseudomonas putida S12. When the phenol concentration in the reactor reaches 2mM, the cells in fermentations without phenol removal are inhibited in growth and phenol production. Growth and phenol production stop after approximately 80h at a phenol concentration in the reactor of 3.8mM. When phenol is removed from the fermentation broth by pertraction, a lower maximum aqueous phenol concentration of 2.6mM is achieved, while the total phenol production increases to 132%, as compared to the fermentation without pertraction. There are indications that the volumetric productivity (mmolL^-1h^-1) increases slightly in the fermentations with in situ pertraction compared to the reference experiments. As expected, the amount of phenol produced per gram biomass (the specific productivity, mmolg^-1L^-1) remains constant in time for all fermentations. The use of pertraction for in situ phenol removal is compared to in situ second phase extraction, in situ solvent impregnated resins and in-stream pertraction. Although the system shows promising results, further modifications such as using a solvent with a higher partition coefficient can improve the overall performance.

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This paper describes a conceptual process design for the production of the model component phenol by a recombinant strain of the micro-organism Pseudomonas putida S12. The (bio)production of the inhibiting component phenol in a bioreactor is combined with direct product removal by membrane extraction (pertraction). Continuous fermentation with the pertraction unit inside the reactor (integrated process), is compared to fed-batch fermentation with the pertraction unit outside the reactor (nonintegrated process). In the nonintegrated process, the bioprocess is completely separated from the pertraction process. An extended model for fermentation, consisting of biomass growth and phenol production combined with product inhibition, cell removal, pertraction with 1-octanol, and regeneration of the solvent by distillation is described with the help of experimental and theoretical data. Running the fermentation process at a lower product concentration results in a more efficient substrate utilization into biomass and phenol. The disadvantage of the integrated process is the need for large distillation columns and a high energy input for solvent regeneration due to the low product concentration in the solvent and the high solvent fluxes. Economic evaluation of the two processes show that to obtain a return of investment of 15%, the product cost price of the integrated process is a factor three lower as compared to that of the nonintegrated process. The benefits of an integrated process will pay off even more for very toxic and inhibiting products that do not allow for a high concentration in the (bio)reactor as compared to phenol.

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This paper evaluates the applicability of aqueous solutions of Pluronics for the removal of phenol in a separation and regeneration process. Experimental results show that Pluronic P103 micelles allow extraction of phenol from aqueous solutions at 30°C. The phenol can be released due to the transition of the Pluronic micelles into unimers with a mild temperature switch from 30 to 8°C. Ultrafiltration membranes provide a barrier between the aqueous Pluronic stripping solution and the aqueous solution in a (bio)reactor containing the desired product. Additionally, a similar UF membrane is used to separate the micelles and unimers from water. Steady state model analysis of the proposed separation and regeneration process are performed to obtain a phenol mass flow rate in the product stream equal to the phenol production rate in the (bio)reactor. Furthermore, the process is analyzed for different process configurations and a cost estimation is made. The results show that for the model product phenol, the process costs are mainly determined by the required membrane area. The proposed process can be suited for products that allow for a higher critical concentration in the (bio)reactor as compared to phenol. The resulting higher driving force for membrane extraction will result in a decrease of the overall process costs. For products with a lower solubility in water, recovery is easy after regeneration of the micellar solvent.

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The applicability of aqueous solutions of Pluronics for the removal of the model product phenol was evaluated. Phenol is a chemical that can be produced by a recombinant strain of the solvent tolerant bacterium Pseudomonas putida S12. However, the growth of the micro-organisms and the phenol production is inhibited at low phenol concentrations. The solubility of phenol in aqueous solutions containing micelles of Pluronics F108, F68, P105, L64, P104, P85, P103 and L122 was determined. Additionally, the regeneration behavior of the Pluronics was studied by determining the solubility of phenol in Pluronic unimers after lowering the temperature of the solution to below critical micelle temperature. The phase behavior of Pluronics in the presence of fermentation broth and the growth of P. putida S12 in the presence of Pluronics were studied. Finally, the results obtained in this study were used to estimate the amount of cooling energy needed to obtain 1 g of phenol using Pluronics P85 and P103.

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The application of extractants in whole-cell biocatalysis can have a positive impact on industrial fermentations, in terms of productivity, total amount of product produced, and cell growth. When a product is continuously removed from the microorganism surroundings, product inhibition will be diminished. The strategy is exemplified using phenol as the product and the extractant is selected for solvent-impregnated resins, which can prevent emulsification problems that are commonly encountered in in situ extractive recovery of fermentation products. A systematic approach for selection of superior extractants in whole-cell biocatalysis is discussed in this paper. Three criteria are taken into account, namely, extractant toxicity (log P o/w values), product selectivity, and extractant regeneration.@en