Continuous bioconversion of n‐octane to octanoic acid by recombinant Escherichia coli (alk+) growing in a two‐liquid‐phase Chemostat

Publisher Website
Google Scholar
Abstract
Escherichia coli is able to grow on sugars in the presence of a bulk n-alkane phase. When E. coli is equipped with the alk genes from Pseudomonas oleovorans, the resulting recombinant strain converts n-alkanes into the corresponding alkanoic acids. To study the effects of growth rate and exposure to a bulk apolar phase on the physiology and the productivity of E. coli, we have grown this microorganism in two-liquid-phase continuous cultures containing 5% (v/v) n-octane. In contrast to batch cultures of wild-tape E. coli grown in the presence of n-octane, cells remained viable during the entire continuous culture, which lasted 200 h. Bioconversion of n-octane to n-octanoic acid by a recombinant E. coli (alk+) in a two-liquid-phase continuous culture was made possible by optimizing both the recombinant host strain and the conditions of culturing the organism. Continuous production in such two-phase systems has been maintained for the least 125 h without any changes in the product concentration in the fermentation medium. The volumetric productivity was determined as a function of growth rate and showed a maximum at a dilution rate D = 0.32 h−1, reaching a continuous production rate of 0.5 g octanoate/L · h (4 tons/m3 · year). © 1993 John Wiley & Sons, Inc.