Succinic acid production from pentose rich sources in Actinobacillus succinogenes

Succinic acid has been put forward as one of the most interesting platform chemicals which can be derived from biomass. This is underlined by the investments made in fermentative production of succinic acid by several companies in recent years. The most common feedstocks for succinic acid production have so far been refined sugars or molasses. There are, however, clear incentives for replacing these feedstocks with a (non-food) biomass derived feedstock. Sugars derived from such feedstock, e.g. agricultural residues or underutilized hemicellulose streams are likely to contain significant quantities of pentose sugars.

In this study, xylose utilization in one of the most prominent natural succinate producers, Actinobacillus succinogenes, was investigated. Apart from succinic acid which is the main product, A. succinogenes also produces formic and acetic acid. The xylose utilization and product formation was investigated in bioreactors operating in continuous mode in order to characterize xylose utilization and product distribution at defined specific growth rates. Under anaerobic (and carboxylating) conditions a succinate yield of 0.66 g succinate per g xylose was obtained. The organism showed a strong tendency for biofilm formation. Continuous cultivations were also made under aerobic conditions, in which case the xylose utilization was low, and no succinic acid was formed. The tendency of biofilm formation was much lower under aerobic conditions.