Engineering of corynebacterium glutamicum for the production of value-added products from mixed-sugar

Abstract

Over the past few years, environmental problems and depletion due to fossil-fuel use have become major issues. One of the solutions is to use biomass, and it has become more important to convert lignocellulose, which exists in large quantities on the earth, into biomass. Lignocellulose, which is mainly composed of glucose, xylose and arabinose, is very cheap, so there has been a lot of effort in the industry to use it to save money, but many micro-organisms could not easily consume pentoses and needed further improvement. Corynebacterium glutamicum is able to produce various substances such as amino acids by using carbon source, which is suitable as a strain for production of value-added product. However, since wild type does not have xylose metabolizing enzyme, it is not easy to consume the mixed-sugar. To solve this problem, previous studies have introduced xylose metabolizing enzymes and made it possible to metabolize xylose through adaptive evolution. In addition, in this study, xylose transport protein was introduced to further activate xylose metabolism, resulting in faster xylose consumption and cell growth. When gamma-aminobutyrate and poly-hydroxybutyrate were produced by consuming mixed sugars, it was confirmed that the yield of the modified strains was similar to that of glucose alone. This shows the possibility of replacing the carbon source from glucose to xylose. Additionally, to increase the gamma-aminobutyrate precursor, the malate dehydrogenase gene was removed and overexpression of the isocitrate dehydrogenase increased gamma-aminobutyrate production.