Research On The Production Of Fumaric Acid By Fermentation With Rhizopus Delemar From Wheat Bran Enzymic Hydrolysate

Fumaric acid is not only a kind of common food and feed additives, but also animportant organic chemical feedstock, it can be widely used in the field of medicineand chemicals. With the depletion of the petroleum supply, it’s urgent to find a newgreen sustainable method for fumaric acid production. The wheat bran is the mainbyproduct during the flour processing, which is rich in carbohydrate, protein,vitamins and minerals. To convert the wheat bran into organic acids by microbialfermentation is an effective way to improve the economic value of wheat bran andproduct fumaric acid greenly and sustainablely. On the basis of the study on thefumaric acid producted from glucose and xylose by Rhizopus delemar CICC41341and the preliminary analyses of the xylose metabolic mechanism, the fumaric acidfermentation from wheat bran hydrolysate by Rhizopus delemar was investigated inthis work. A preprocessing method for wheat bran with high cellulase hydrolysisrate was obtained through the investigation of pretreatment effect of the bran; theacid yield in the separate hydrolysis and fermentation was improved bydetoxification of hydrolysate, medium optimization and other means; the optimalfermentation condition was obtained via regulating and controlling the maininfluencing factors of simultaneous fermentation. The main results were as follows:（1） Under the certain fermentation condition with the glucose as the carbonsource, the optimal medium components were glucose100g/L,（NH₄）₂SO₄4.0g/L，yeast extract powder0.40g/L，KH₂PO₄0.20g/L，FeSO₄0.02g/L，ZnSO₄0.40g/L，MgSO₄0.30g/L，CaCO₃40g/L；under this fermentation craft, the fumaric acidyield was36.12g/L, the rate of conversion was40.47%.（2） Under the certain fermentation condition with the xylose as the carbonsource, the optimal medium components were xylose80g/L,（NH₄）₂SO₄4.0g/L，yeast extract powder0.30g/L，KH₂PO₄0.50g/L，FeSO₄0.02g/L，MnSO₄0.20g/L，MgSO₄0.30g/L，CaCO₃40g/L；under this fermentation craft, the fumaric acidyield was28.16g/L, the rate of conversion was36.46%. The result of the analysisof pentose phosphate pathway in the Rhizopus delemar CICC41341indicated thatthe xylulokinase in PPP was the key rate-limiting enzyme, it can significantlyimprove the ability of utilizing xylose and enhance the yield of fumaric acid afteractivated by Mg²⁺、Mn²⁺. （3） The proper preparation method of wheat bran hydrolysate,which waspretreatment of wheat bran with Alkaline hydrogen peroxide and the detoxificationof hydrolysate with macroporous resin NAK-Ⅱ,was obtained in the separatehydrolysis and fermentation. The medium of fumaric acid fermentation from wheatbran hydrolysate by Rhizopus delemar CICC41341was optimized according to theResponse surface methodology, the optimal fermentation craft were sugarconcentration of the hydrolysate80.0g/L,（NH₄）₂SO₄2.0g/L, yeast extract powder0.29g/L, MgSO₄0.26g/L、MnSO₄0.07g/L，FeSO₄0.05g/L，CaCO₃40g/L，underthis condition, the fumaric acid yield was27.42g/L, the rate of conversion was38.55%. The results suggested that the separate hydrolysis and fermentation wasappropriate for the fumaric acid production from wheat bran by Rhizopus delemar.（4） The method of alkaline high temperature and high pressure was adopted topretreat the wheat bran for the simultaneous saccharification and fermentation. Thepretreatment condition was optimized through orthogonal design, the optimalcondition was temperature120℃，time40min, the concentration of NaOH1.0%.The optimal fermentation craft was determined according to the single factorexperiments, it was hydrolysis temperature40℃, enzyme content0.732IU/g, rotatespeed200r/min, wheat bran content100g/L, delay time of inoculation36h. Thefumaric acid yield of6.06g/L was obtained after incubation for7days. The resultshowed that separate hydrolysis and fermentation to product fumaric acid byRhizopus delemar was better than that of simultaneous saccharification andfermentation.