Simultaneous Saccharification And Fermentation Of Alkali-pretreated Corncob To Fumaric Acid By Rhizopus Oryzae

Fumaric acid, as an important platform for the four carbon compounds, has widely application in chemical industry, food, medicine, etc. Due to the chemical method of high energy consumption, environmental pollution shortcomings, spurred the search for a environmentally friendly method of preparation and biosynthesis of fumaric acid. Therefore, biosynthesis method became one of research hot spots in recent years. In this paper, Rhizopus oryzae served as the fermentation strain, utilized alkali-pretreated corncob as the carbon source to produce fumaric acid under the simultaneous saccharification fermentation mode. After the fermentation, the fungus balls were collected to extract chitosan. The main results were as follows:(1)Simultaneous saccharification and fermentation of alkali-pretreated corncob to fumaric acid by Rhizopus oryzae was realized, and the optimal fermentation conditions were citric acid buffer system of pH 4.8, fermentation temperature of 38℃, rotating speed of 130 rpm, cellulase dosage of 25FPIU/g cellulose. Compare simultaneous saccharification fermentation(SSF)with separate hydrolysis and fermentation(SHF) and pure glucose fermentation. Fumaic acid production in SSF process was 14.72 g/L, which was higher than SHF 12.28% and pure glucose fermentation 31.55%, respectively. Moreover, SSF mode was conducive to obtain a high fumarase activity at a longer time.(2)At 10%(w/v) substrate concentration, fumaric acid maximum production was 28.65g/L,productivity is 0.40 g/(L.h); at 15%(w/v) substrate concentration, maximum production was35.22 g/L, productivity was 0.27 g/(L.h); at 20%(w/v) substrate concentration direct fermentation,production was 19.13 g/L;(3) Multi-stage fermentation at 20%(w/v) substrate concentration was conducted. The fumaric acid production of two-stage SSF mode was 34.45 g/L; the three-stage SSF mode could produce 41.32 g/L fumaric acid with a productivity of 0.23 g/(L.h); and the the fumaric acid production of four-stage SSF mode was 33.32 g/L. Therefore, the three-stage SSF mode promoted simultaneous saccharification and fermentation of alkali-pretreated corncob to fumaric acid by Rhizopus oryzae at high substrate concentration.(4)The performance characterization of chitosan extracted form SSF fungus balls was compared with crab chitosan, including crystallinity determination by X-ray diffraction spectrum,infrared spectral analysis, thermogravimetric analysis. The deacelation degree of fungal chitosan was 90%; viscosity of 20g/L fungal chitosan and crab chitosan solution were around 2cP and70cP; number average molecular weight Mn, heavy molecular weight Mw and dispersion coefficient D of fungal chitosan were 1532.3g/mol, 2578.2g/mol and 1.68.