Andrew Timothy Boam

A membrane bioreactor for biotransformations of hydrophobic molecules

The Membrane Bioreactor for Biotransformations (MBB) is based on the aqueous/organic two-phase system, and uses a tubular silicone rubber membrane to separate the two liquid phases. This avoids the key problem associated with direct contact two-phase processes, specifically, product emulsification. The bakers yeast mediated reduction of geraniol to citronellol was used as a model biotransformation to demonstrate MBB operation. Values for the overall mass transfer coefficient were determined for geraniol, (2.0 x 10(-5) ms-1), and for citronellol, (2.1 x 10(-5) ms-1) diffusion across the silicone rubber membrane. Using these values, and the specific activity of the biocatalyst (5 nmols-1g biomass-1), a suitable membrane surface area: biomass ratio was determined as 2.4 x 10(-3) m2g biomass-1. The bioreactor was operated at this surface area: biomass ratio and achieved a product accumulation rate 90-95% that of a conventional direct contact two-phase system. The slight reduction in product accumulation rate was shown not to be due to mass transfer limitations with respect to reactant delivery or product extraction. Copyright 1998 John Wiley & Sons, Inc.

Membrane aromatic recovery system (MARS): lab bench to industrial pilot scale

This article describes a novel process for recovery of aromatic amines and phenolic compounds form wastewaters, the membrane aromatic recovery aromatic system (MARS). Laboratory work on wastewaters containing aniline and phenol will be presented, including data demonstrating removal and recovery of each chemical in a sufficiently pure form to allow recycling into a chemical production process. This article also describes successful scale-up and operation of the process through pilot trials at Solutia, UK. Process economics are discussed and data showing the potential for application of the process to a wide range of organic chemicals are presented.

Epoxidation of 1,7‐octadiene by Pseudomonas oleovorans in a membrane bioreactor

A growing cell culture of Pseudomonas oleovorans was used to biotransform 1,7-octadiene to 1,2-epoxy-7,8-octene in a continuous-flow bioreactor with an external membrane module. A dense silicone rubber membrane was used to contact an organic phase, containing both the reactant (1,7-octadiene) and the growth substrate (heptane), with an aqueous biomedium phase containing the biocatalyst. Heptane and octadiene delivery to the aqueous phase, and epoxide extraction into the solvent, occurred by diffusion across the dense membrane under a concentration-driving force. In addition, a liquid feed of heptane and octadiene was pumped directly into the bioreactor to increase the rate of delivery of these compounds to the aqueous phase. In this system 1,2-epoxy-7,8-octene accumulated in a pure solvent phase, thus, product recovery problems associated with emulsion formation were avoided. Furthermore, no phase breakthrough of either liquid across the membrane was observed. In this system, the highest volumetric productivity obtained was 30 U.L-1, and this was achieved at a dilution rate of 0.07 h-1, 70 m2. m-3 of membrane area, and a steady-state biomass concentration of 2. 5 g.L-1. The system was stable for over 1250 h. Decreasing the dilution rate led to an increased biomass concentration, however, the specific activity was significantly reduced, and therefore, an optimal dilution rate was determined at 0.055 h-1. Copyright 1999 John Wiley & Sons, Inc.

Optimisation Of The Kinetics Of The Stereoselective Reduction Of Geraniol To Citronellol In A Two Liquid Phase System

Kinetics of the stereoselective reduction of geraniol to citronellol by bakers yeast (Saccharomyces cerevisiae) were studied by examining the influence of system parameters on the reaction rate in an aqueous/organic two phase system. This system was used due to the hydrophobic nature of the reactant and product, and enabled simple and accurate measurement of the kinetics, and hence optimisation. This reaction system provided “pseudo steady state” aqueous conditions in batch experiments over short time periods, and therefore allowed direct determination of the biotransformation rate. The maximum biotransformation activity was determined to be 300 nmol min-1 g biomass-1. Of the parameters tested those which most significantly affected the biocatalytic activity were; biomedium pH, reactant concentration, solvent type, and aeration. The optimum pH was found to be 9.5, and this was associated with increased intra-cellular NADPH concentrations. Slight substrate inhibition with geraniol occurred at concentratio...

Chapter 8 – Membrane Aromatic Recovery System (MARS) – A new process for recovering phenols and aromatic amines from aqueous streams

Phenolic compounds (chemicals such as phenol and its derivatives) are used in phenolic resins, polycarbonates, biocides and agrochemicals. Aromatic amines (chemicals such as aniline and its derivatives) are used in a wide range of consumer products, including polyurethane foam, dyes, rubber chemicals and pharmaceuticals. The factories that manufacture and/or use these types of chemicals often create aqueous waste streams containing significant concentrations (0.1-10wt%) of these chemicals. Both aromatic amines and phenolic compounds are toxic and many of them are also carcinogenic. Tightening legislation in many countries calls for dramatic reductions in emissions of these species. A variety of processes have been proposed for treatment of these aromatic amine or phenolic compound containing wastewaters. Off-site disposal (landfill, deepwell injection) and biodegradation result in the compounds, which have typical values in the range US

Demonstration of Molecular Purification in Polar Aprotic Solvents by Organic Solvent Nanofiltration

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Nanofiltration process for the nutritional enrichment and refining of rice bran oil

20 per kg, being lost. These compounds have high boiling points and low vapour pressures. Hence, processes that rely on liquid-gas phase transition, such as distillation and pervaporation, have high-energy requirements. The use of adsorbents, such as activated carbon [1-4] or resins [58], is usually expensive due to difficulties and complexity in the regeneration stage. Problems associated with the use of solvent extraction [9-13] arise with phase separation [14] and contamination of the wastewater with solvent [15] due to the intermediate polarity of the compounds, which require moderately water soluble solvents.