Engineering Actinobacillus succinogenes for succinate production from xylose

If succinate was fermentatively produced at a price competitive with that of oil-based maleic anhydride, it could replace maleic anhydride as the precursor of many bulk chemicals, which a total $15 billion/year market. Actinobacillus succinogenes is among the best natural succinate producers, making it a natural choice for industrial succinate production. A. succinogenes grows on lignocellulose’s most abundant sugars, and it can ferment multiple carbon sources simultaneously, suggesting that it could be used in a lignocellulose-based succinate production process.

Three independent cultures of A. succinogenes have been evolved for fast growth on xylose. The three evolved strains showed a 25% increased succinate yield on glucose and a 20% increase on xylose. The three evolved strains have in common independent mutations in and upstream of the xylose permease gene, xylE, as well as in the translation elongation factor EF-G.  Two evolved strains carry independent mutations in the NAD synthesis pathway. Overexpression, RT-qPCR, NAD(H) quantitation, and in vitro translation elongation assays were used to investigate these mutations. The results of these experiments, as well as the effects of these mutations on growth and succinate yields, will be discussed.