The Basic Research On Fermentation Coupled Separation Of Succinic Acid Production

Succinic acid is a valuable four-carbon platform chemical for several industrial products including food,pharmaceuticals and biodegradable plastics.Succinic acid bioproduction has become the trendency because of being environmentally friendly,use of renewable resources and CO₂ immobilization.Owing to the broad spectrum of the carbon source,toxicity little and the strong productioncapability,Actinobacillus succinogenesCICC11014 becomes the most potential producer for succinic acid production.In this paper the work was aimed at solving questions such as high production cost and difficulty in separation.First of all,three kinds of fermentation medium and oxygen control were explored and the suitable fermentation medium was determined.The appropriate fermentation medium?1L?was that glucose 20 to 100 g,yeast extract powder 15 g,NaCl 1.0 g,MgCl2·6 H₂O 0.427 g,CaCl₂0.2 g,sodium acetate,1.36 g and KH₂PO₄ 3.2 g,K₂HPO₄ 1.6 g,Na₂S·9 H₂O 0.16 g,alkali magnesium carbonate 20 60 g,initial pH7.0,and Na₂S solution was sterilized by membrane.The highest succinic acid yieldwas 0.81?g/g?.Influenceson the cheap substrate?molasses?and nitrogen source?corn starch powder?on the production of succinic acid fermentation were explored.The results showed that corn liquid powder could take the place of yeast extract powderand improved the succinic acid yield,but Actinobacillus succinogenesCICC11014 could not use ammonium sulfate as the nitrogen source alone.The optimal nitrogen source was 5 g/L yeast extract powder and 10 g/L corn liquid powder.The optimal initial sugarcane molasses concentration as carbon source was 100 to 150g/L.Second,sugaring-out and salting-out extraction basing on ionic liquids were developed to extract succinic acid.Among these five investigated ionic liquids,the ionic liquid with BF4-and OTF-anion showed the ability to form two phases not only with glucose but also with salts.However,the ionic liquid with Br-anion could not form aqueous two-phase system with glucose,but with salts.The phase ability order of sugaring-out extraction was [Bmim]BF₄> [Bmim]OTF >[Emim]BF₄,salting-out extraction was K₂CO₃>?NH₄?₂SO₄.Additionally,the performance of the aqueous two-phase systems in the extraction of succinic acid was investigated.The results indicated that ionic liquid and glucose aqueous two-phase system was suitable for the extraction of succinic acid and the distribution behavior of succinic acid depended on not only the concentrations of ionic liquids and glucose,but also the pH.The partition coefficient?2.53?and recovery?74.25%?of succinic acid were obtained by a sugaring-out system consisting of 45% [Bmim]BF4/30%glucose?w/w?at pH 2.0.Over 96% glucose was remain in the glucose-rich bottom phase could be utilized to produce succinic acid.When using real fermentation broth,the recovery of succinic acid was 73.71%,the removal ratio of cells and proteins were 99.26% and 89.79%,respectively.Relatively high extractabilities were obtained by using the salt solutions.However,The allocation behavior of succinic acid of salting-out extraction basing on ionic liquid had nothing to do with the system of pH,but was mainly affected by the initial succinic acid concentration.The best salting-out extraction system was 30% [Hmim]Br /10%?NH₄?₂SO₄?w/w?,and the extractabilities of succinic acid was 69.98%,but it is not suitable for extraction of high succinic acidconcentration.Finally,ionic liquid based sugaring-out extraction coupled with fermentation of succinic acid was studying.Ionic liquids was recovered using 20%IL/20% salts and reused again,thetotal recovery of succinic acid was 83.68%.Actinobacillus succinogenes CICC11014 could use enriched glucose phase as carbon source,and suggested that it was feasibilityto separation coupled with fermentation.