Fermentative Production Of Succinic Acid From Spiirt-based Distillers’grains

Succinic acid, a C4-dicarboxylic acid, is one of the most important platform chemicals, andis widely used in the food, chemical, and pharmaceutical industries. Spirit-based distillers’grains (SDG) is the main by-product of the Chinese liquor industry. Given the substantialgrowth in the production of Chinese liquor, approximately100million tons of SDG iscurrently produced every year. The study of fermentative production of succinic acid fromspirit-based distillers’ grains is meaningful. SDG can be used as a promising raw material forsuccinic acid production. The compositions of SDG and PSDG was measured and hydrolysismethod was investigated, production of succinic acid from SDG and PSDG was conducted inthis paper.SDG was measured to contain39.76%nitrogen-free extract,17.15%protein,37.91%cellulose,6.02%lipid, and9.16%ash and12.35%starch. Spirit-based distillers’ grains (SDG)treated with enzyme hydrolysis was used as a material for fermentative production of succinicacid by Actinobacillus succinogenes. When the hydrolysis reaction was solely catalyzed bycellulase or amylase under its optimum temperature and pH, the corresponding hydrolysisrates of cellulose in SDG and starch in SDG were44.04%and92.26%, respectively. Whilehydrolysis using cellulase and amylase step by step (HSS), the later hydrolysis reaction couldbe restrained. Otherwise, the yield of reducing sugar in hydrolysis using cellulase andamylase simultaneously was about150mg/g SDG, the same as that of HSS. Using hydrolysisand fermentation separated processes,58.4g/L reducing sugar was obtained resulting28.8g/Lsuccinic acid with a yield of72mg/g SDG. However, using the procedure that firstlyhydrolysis of SDG with cellulase, then starch in SDG was simultaneous saccharification andfermentation,32g/L succinic acid was achieved with a yield of133mg/g SDG.PSDG contained54.73%nitrogen-free extract,24.07%protein,5.52%cellulose,7.64%lipid, and8.04%ash, with starch and free amino acid contents of32.66%and3.06%,respectively. The optimal concentrations of α-amylase (for liquefaction) and glucoamylase(for saccharification) were90U/g PSDG and73U/g PSDG, respectively. The succinic acidconcentration was maximal and the residual sugar concentration was at a minimum when theconcentration of hydrolyzed sugar was55g/L at a PSDG concentration of180g/L. Thedemonstration that the succinic acid concentration reached37.2g/L when biotin was suppliedat200μg/L in the PSDG medium suggests that biotin was one of the key factors thatinfluenced succinic acid production by A. succinogenes. Yeast extract and thiamine have nosignificant effect on succinic acid production. The effect of pH controlling agent such asMg(OH)2combined with NaOH, saturated Na2CO3, saturated NaHCO3and MgCO3wasinvestigated. When pH was controlled by saturated Na2CO3and MgCO3the concentration ofsuccinic acid is36.9g/L and38.6g/L respectively. The yield is205mg/g PSDG and214mg/g PSDG, successively. MgCO3can be replaced by saturated Na2CO3which is cheaper.SDG is a promising raw material for succinic acid production.