The Potential of Lactic Acid Bacteria As Microbial Factory for Pentanol Isomer Production

Due to modern society´s reliance on petroleum-derived fuels and a limited supply of this non-renewable resource, recent approaches have aimed at constructing microbial hosts for sustainable production of alcohol by engineering a number of organisms such as Clostridium acetobutylicum, Escherichia coli and Saccharomyces cerevisiae. However, lactic acid bacteria (LAB) may be more suitable as host organisms since they potentially tolerate organic acids, alcohol and low pH better. With a metabolic engineering-, screening–, and adaptive evolution approach this project proposes to utilize C5 and C6 rich waste streams as substrate for microbial conversion to alcohol. The research plan for elucidating the potential of alcohol production in LAB include screening of tolerance towards alcohol and lignocellulosic inhibitors, adaptive evolution of LAB for improved alcohol tolerance and metabolic engineering of both a LAB model strain as well as an industrial strain. By exploiting the native pathways for amino acids, several higher alcohols may be produced upon insertion and overexpression of an alcohol decarboxylase and a ketoacid decarboxylase. A model LAB strain is currently under construction. Two LAB strains were selected for adaptive evolution of which one showed improved tolerance towards a pentanol isomer after approximately 200 generations of growth in the presence of increasing selective pressure.