Production of Succinic Acid From Basfia succiniciproducens

Basfia succiniciproducens is a facultative anaerobic capnophilic bacterium, isolated from rumen, that naturally produces high amounts of succinic acid by fixing CO2 and using fumarate as final electron acceptor. This metabolic feature makes it one of the ideal candidates for developing biotechnological industrial routes that could eventually replace the polluting and environment unfriendly petrochemical ones that are still main sources for the production of this value-added compound. In fact, due to the large number of applications of succinic acid that range from the more traditional ones as food additive or pharmaceutical intermediate to the most recent as building block for biopolymers and bioplastic, increasing demand and market size growth are expected in the next years. In line with a “green revolution” needed to preserve our environment, the great challenge is the establishment of commercially viable production processes that exploit renewable materials and in particular preferably non-food lignocellulosic biomasses and waste products. In this review, we describe the currently available literature concerning B. succiniciproducens since the strain was first isolated, focusing on the different renewable materials and fermentation strategies used to improve succinic acid production titers to date. Moreover, an insight into the metabolic engineering approaches and the key physiological characteristics of B. succiniciproducens deduced from the different studies are presented.

Effect of neutralizing agents in the preparation of succinic acid from oil palm trunk

Neutralization is an important process to control the pH required for enzymatic saccharification of pretreated biomass followed by fermentation for biochemical conversion. In this study, the production of succinic acid as a potential C4 building block was investigated by utilizing lignocellulosic biomass in the form of oil palm trunk (OPT). The effect of different neutralizing agents (NaOH, KOH and NH4OH) on the enzymatic saccharification of oxalic acid-pretreated OPT and subsequent succinic acid fermentation by Actinobacillus succinogenes ATCC 55618 was investigated. The results showed that all neutralizing agents tested were able to assist in the recovery of fermentable sugars with concentrations ranging from 38.1 to 39.6 g/L. However, during succinic acid fermentation, it was found that the soluble NH4-oxalate salt formed severely inhibited succinic acid fermentation compared to Na and K, thereby decreasing the succinic acid production from 14.0 g/L (using NaOH) to 1.0 g/L (using NH4OH). In particular, Na-and K-oxalate did not exhibit apparent inhibition for both the saccharification and fermentation processes. Hence, the choice of neutralizing reagent is essential to prevent inhibition in the preparation of succinic acid from lignocellulosic biomass.

Surface Modification of a Graphite Felt Cathode with Amide-Coupling Enhances the Electron Uptake of Rhodobacter sphaeroides

Microbial electrosynthesis (MES) is a promising technology platform for the production of chemicals and fuels from CO2 and external conducting materials (i.e., electrodes). In this system, electroactive microorganisms, called electrotrophs, serve as biocatalysts for cathodic reaction. While several CO2-fixing microorganisms can reduce CO2 to a variety of organic compounds by utilizing electricity as reducing energy, direct extracellular electron uptake is indispensable to achieve highly energy-efficient reaction. In the work reported here, Rhodobacter sphaeroides, a CO2-fixing chemoautotroph and a potential electroactive bacterium, was adopted to perform a cathodic CO2 reduction reaction via MES. To promote direct electron uptake, the graphite felt cathode was modified with a combination of chitosan and carbodiimide compound. Robust biofilm formation promoted by amide functionality between R. sphaeroides and a graphite felt cathode showed significantly higher faradaic efficiency (98.0%) for coulomb to biomass and succinic acid production than those of the bare (34%) and chitosan-modified graphite cathode (77.8%), respectively. The results suggest that cathode modification using a chitosan/carbodiimide composite may facilitate electron utilization by improving direct contact between an electrode and R. sphaeroides.