A new applicability of wastewater of dextran fermentation (WWDF) for biological production of succinic acid with A. succinogenes CCTCC M2012036 was reported in this work for the first time. Notably, K2CO3 was used instead of MgCO3 in the pH regulating process for operational feasibility and a cell immobilization methodology by attaching cells on cotton fibrous matrix was adopted for cell recycle. The initial sugar concentration as well as matrix usage was optimized by investigating the cell growth, succinic acid concentration and yield. A rotated fibrous bed bioreactor was designed and constructed in order to increase the total cell amount and facilitate mass transportation in the fermentation system, and an average succinic acid yield, concentration and productivity of 0.82 g/g, 56.5 g/L and 1.28 g/L/h were realized in the repeated fed-batch fermentation, respectively. This research gave light to the optimization of succinic acid production towards a more cost-effective and operable direction.

Muconic acid (MA) is a promising bulk chemical due to its extensive industrial applications in the production of adipic acid and other valuable, biodegradable intermediates. MA is heretofore mainly produced from petrochemicals by organic reactions which are not environmentally friendly or renewable. Biological production processes provide a promising alternative for MA production. We designed an artificial pathway in Escherichia coli for the biosynthesis of MA using the catechol group of 2,3-dihydroxybenzoate, an intermediate in the enterobactin biosynthesis pathway. This approach consists of two heterologous microbial enzymes, including 2,3-dihydroxybenzoate decarboxylase and catechol 1,2-dioxygenase. The metabolic flow of carbon into the heterologous pathway was optimized by increasing the flux from chorismate through the enterobactin biosynthesis pathway and by regulating the shikimate pathway. Metabolic optimization enabled a concentration of 605.18 mg/L of MA from glucose in a shaking flask culture, a value nearly 484-fold higher than that of the initial recombinant strain. The results indicated that the production of MA from this pathway has the potential for further improvement.

•ATPS was developed for separation of SA from actual fermentation broth.•The recovery of SA and the removal of glucose and cells were more than 90%.•The total yield of succinic acid crystal was 77.3% with a purity SA of 98.7%.Aqueous two-phase system was studied for the extraction of succinic acid (SA) produced by Actinobacillus succinogenes from the fermentation broth. Various hydrophilic solvents and inorganic salts were used to form the aqueous two-phase system for SA extraction, among which an acetone/ammonium sulfate aqueous two-phase system was investigated in detail, including examination of the phase diagram, effects of phase composition and pH on partitions, removal of cells and proteins from the fermentation broth, and recovery of ammonium sulfate. Under optimized conditions, with the fermentation broth pH value of 2 and aqueous two-phase system composed of 35% (w/w) acetone and 15% (w/w) ammonium sulfate, the recovery of SA from the fermentation broth was 94.4% with the removal of 93.6%, 98.1%, and 78.5% glucose, cells, and proteins, respectively. The total SA yield was 77.3% and the purity of SA was 98.7%. With the addition of methanol, 95.9% of ammonium sulfate in the salt-rich phase could be recovered, which indicated less waste discharge in SA extraction using the aqueous two-phase system.

•Charged polypropylene microfiber membrane first used for cell immobilization.•Operational parameters were optimized and cell reusability was good.•Biofilm formed to favor the production of succinic acid.•Cell-immobilized membrane bioreactor constructed to perform fermentation.A new applicability of cell-immobilized system for biological production of target chemical was reported in this work. A. succinogenes CCTCC M2012036 was immobilized on positively charged polypropylene microfiber membrane by physical interaction and were used for converting glucose into succinic acid. Glucose consumption and succinic acid production kinetics were investigated for optimizing the operational parameters. The cell-immobilized membrane presented good reuse stability, and six cycles of fermentation without activity loss were realized with an average succinic acid yield of 0.83 g/g. Importantly, a biofilm was formed which favored the production of succinic acid. A microfiber membrane bioreactor was further constructed with the cell-immobilized membrane to perform fermentation in a larger scale, and the yield and productivity of succinic acid were 0.82 g/g and 1.04 g L−1 h−1 using a fed-batch strategy. By combining mesoporous support with biotechnological techniques, this work offered a prospect of adopting reusable cells feasible for industry.