Study Of Preparation Of Rice Straw Hemicellulosic Hydrolysate For Production Of Xylitol By Fermentation

Xylitol (CH2OH-CHOH-CHOH-CHOH-CH2OH) is a polyol, with a sweetening power similar to sucrose and a calorie similar to glucose. It is used as a nutrition and a cure for diabetes patients because it can regulate abnormity of metabolism. It is also used for salvaging acetone-body patients because of its resisting acetone-body effect. It can slower the productivity of fatty acid in plasma, but can t result in the rise of blood sugar. It is also used as a medicine for protecting liver. It has good heat-stability and never reacts with amino acids under heating, so it is confected all kinds of preparations for nutrition medicines together with amino acids. As a food, it can defend decayed tooth. Besides, it is applied abroadly in national defence, plastic and light industry.At present, xylitol is produced by chemical method in industry. But chemical method has high cost of production and serious pollution in environment. The production of xylitol by fermentation of hemicellulosic hydrolysates becomes a hotspot. Aiming at many outgrowths restraining fermentation of hydrolysates by microorganism, investigators carry through the studies on how to detoxify hydrolysates more efficiently, how toimprove fermentability of the hydrolysates, how to enhance adaptability of microorganism to hydrolysates and how to increase the transformation of xylose from hydrolysates by finding appropriate conditions in the fermentation, and they have enjoyed many fruits.The discourse studies the preparation of rice straw hemicellulosic hydrolysate for production of xylitol by fermentation. Firstly, on the basis of single factor experiment, the optimal hydrolysis condition established by perpendicular design is sulfuric acid concentration 3%, reaction time 1.5h, hydrolysis temperature 120℃, liquid to solid ratio(mg/L) 10:1. Under the condition, xylose yield 77.0%~94.2% (a=0.05) is obtained to increase xylose yield in hydrolysis and the utilization of hemicellulose. Secondly, several methods for detoxification of hydrolysate are compared which are organic solvents, macroporous adsorption resins and activated charcoal combined with overliming or neutralization. Two methods are confirmed which are overliming with calcium hydroxide followed by S-8 macroporous adsorption resin or by activated charcoal. The influence of temperature, pH, reaction time and liquid to solid ratio on detoxification of hydrolysate by S-8 macroporous adsorption resin and activated charcoal is considered. The detoxification condition by S-8 macroporous adsorption resin is temperature 35℃, pH6, reaction time 8h, liquid to solid ratio 5:1, the detoxification condition by activated charcoal is temperature 65 ℃, pH5, reaction time 10h, liquid to solid ratio 40:1. Under above conditions, the...