Study On Producing Xylitol By Biological Fermentation With The Hydrolysate From Hazelnut Shell

Xylitol is a kind of hydroxyl alcohol sugar that sweetness is about 100%of the sucrose, and is an important chemical production. At present, it has been widely used in food, medicine and other industries. With the increase of corn cob cost which the main raw material of xylitol production, resource competition is becoming increasingly, all the countries to seek alternative resources of interesting is increasing in the world. Hazelnut shell has lower protein and other nutrients, but the content of hemicellulose and cellulose is higher, has the potential to become a corn cob alternative. In this study, we analysis the primary composition of Liaoning hazelnut shell, clearly that hazelnut shell is natural carbon source to product the xylitol, optimized that the key technics of hazelnut shell acid hydrolysis, neutralization, immobilized Candida yeast cells and fermenting xylitol, and investigate the reuse of immobilized cells. In order to effectively use hazelnut shell to provide new ideas and to lay the foundation for the application of hazelnut shell biological production of xylitol.(1) This paper separartely use muffle furnace ignition method, dodecyl sodium sulfate chemical method, admitted to the coomassie brilliant blue method, soxhlet extraction method detected the primary composition of Liaoning hazelnut shell ash, hemicellulose, cellulose, protein and crude fat content. Hazelnut shell main components:36.83±1.23%of hemicellulose,22.34±0.95%of cellulose,1.44±0.19%of crude protein,4±0.58%of crude fat,1.34±0.04%of ash. Indicates that the hazelnut shell contain wealth of hemicellulose, is the good raw material for production of xylose, the natural carbon source for fermentation preparation of xylitol.(2) The hazelnut shell as raw material, using dilute sulfuric acid hydrolysis to product xylose. Investigated separately the effect of hydrolysis solid-liquid ratio, hydrolysis time and hydrolysis temperature on xylose concentration. By response surface analysis method, the optimized acid solution parameters:dilute sulfuric acid concentration for 3.21%, hydrolysis temperature for 126.21℃, hydrolysis time for 166.32 min, solid-liquid ratio for 1:6, xylose concentration is the highest, reaching 50.52 mg/mL, hydrolysate containing lower monosaccharide and fermentation inhibitor concentration.(3) The effect of neutralization temperature, pH value and neutralization time on the concentration of xylose was investigated by using the lime milk neutralization method. The optimization process was as follows:the neutralization temperature was 70℃, neutralization pH value was 9, and the neutralization time was 10in, the xylose concentration was 48.24 mg/mL(4) After a simple removal of toxicity hemicellulosic hydro lysate, use it as carbon source for fermentation, calcium alginate as carrier, the immobilization of Candida tropicalis cells. The influence of sodium alginate concentration, calcium chloride concentration and curing time on the xylitol concentration. Analysis and optimization the process conditions for preparation of immobilized yeast cells:3%sodium alginate and 1%calcium chloride, the curing time is 8 h, xylitol concentration is 26.04 mg/ml by orthogonal method.(5) The immobilized cells were recovered, repeated 6 times after fermentation, xylitol yield average is 45.9±0.98%. Show that yeast cells immobilized in the concrete can be reused, can be completed 6 repeated batch fermentation, particle shape remained good integrity, volume reduction in the standard range, strong stability, saving the cost, compared to free cells of Candida species has great potential and advantages, and is more suitable for large-scale industrialized production.(6) By the combination of single factor test and orthogonal test method. Investigated separately the initial concentration of xylose, speed, fermentation time, fermentation temperature, nitrogen source added, immobilized yeast gel column and hemicellulose hydro lysate medium volume ratio and pH on the effect of xylitol yield. Optimization analysis of the main factors under the condition of shaking flask, established the optimization fermentation conditions:0～24 h,210 r/min; 24～72 hours,120 r/min of speed,5ml of nitrogen addition,1:4 of volume ratio, xylitol rate was 47.16%.