In-situ recovery of carboxylic acids from fermentation broths through membrane supported reactive extraction using membrane modules with improved stability

Abstract

Membrane supported reactive extraction (MSE) coupled to back-extraction (MSBE) using a new type of Teflon (PTFE) capillary membrane contactor was studied for the in-situ removal of carboxylic acids from aqueous streams, e.g. fermentation broths. The use of microporous membranes as extraction interface helps avoiding emulsification problems, allows the use of extreme phase ratios, and protects microorganisms, as they are less affected by solvent toxicity during in-situ extractions. The use of PTFE capillary membranes is suitable for long-term use due its high chemical and thermal stability.

A simple toxicity screening identified n-decanol with tri n-octyl amine (TOA) as a suitable solvent. MSE experiments were performed using membrane contactors (0.005 m2 to 0.15 m2), working with solvent to feed phase ratios down to 1:40 (mass based). The in-situ removal of lactic acid out of fermentation broths using lactobacillus plantarum led to a glucose conversion rate of 80 mol%. Additionally, a concentration factor up to 7.8 could be shown during back-extraction.