Citric Acid Production From Hemicellulose Of Steam Exploded Corn Stalk By Solid-state Fermentation

Due to the depletion of fossil energy and environmental degradation in the world,lignocellulosyl-based chemicals has become a hot researched spot in biomass engineering in recent years.Lignocellulose is mainly composed of cellulose,hemicellulose and lignin.There are more studies on cellulose and lignin,while the reports on the utilization of hemicellulose is relatively limited.Hemicellulose is a carbohydrate with larger quantities in cellulosic material.It is one of the most abundant and cheapest renewable resources on the earth,which has great explored potentiality and utilized value.Hemicellulose is mainly composed of pentose.And hemicellulose is more easily to be degraded compared to cellulose.The effective use of hemicellulose will reduce the cost in the fermentation industry.Currently,a small number of available studies on hemicellulose utilization are mainly focusing on the chemicals production by fermentation from hemicellulose hydrolysate,but there is no research about solid fermentation of hemicellulose.Therefore,the utilization of hemicellulose to produce citric acid as target product was studied in the present study,and the research results were given as follows:(1)The effects of steam explosion on the dissociation degree of hemicellulose and the dissolution of monosaccharides were studied.The changes of structural and functional groups were characterized by infrared spectroscopy and ultraviolet spectroscopy.Then the operating parameters of steam exdplosion were optimized,when steam explosion was operated at 1.0 MPa for 5 min,or 1.3 MPa for 3 min,the sugar concentration in hemicellulose hydrolysated is higher.(2)The periodic peristalsis-enhanced high solid enzymolysis of hemicellulose from steam exploded corn stalk with low enzyme loading were studied.The results showed that when the solid content was 25%,and enzyme loading was 0.1 FPU/g substrate,the enzymolysis time was 4h with periodic peristalsis,which was shortened by 6 times,and the total sugar concentration also increased by 23.8%compared with those in the static enzymolysis.(3)The gas double-dynamic fermentation with high-solid loadings of citric acid from hemicellulose of steam explosion stalk was studied.It was confirmed that the gas double dynamic technique was an effective strengthening technique,which could increase the yield of citric acid by 74%.