Xylitol Production From Bamboo Inner By Hydrolysis And Fermentation

From cross section of bamboo pole, the wall could be classified into three parts, with the direction of outer to inner, such as skin( mostly stone cells), meat ( organization of vascular bundles ), and bamboo inner ( mostly parenchyma cells ). The physical properties of bamboo inner show that it is more bulky in structure and weak in mechanical strength because of more non-fiber elements in this layer. Therefore, bamboo inner is discarded during board forming and pulping processes. Development and utilization of bamboo inner will contribute to reducing resource waste and improving the comprehensive utilization of bamboo. In the experiment, bamboo inner was took as raw material to produce xylitol by fermation with Candida tropicalis, and during the process, main factors were investigated in this paper, such as detoxification of hemicellulosic hydrolysate, adaptation, and ermentation parameters optimization.The optimal hydrolysis conditions were obtained by orthogonal experiment: dilute sulfuric acid concentration 3.5 %, reaction temperature 100℃, reaction time 2.5 h and ratio of liquid to solid 10:1, under which the pentose yield could reach to 72.61 %. In additon, the hydrolyzate monosaccharide was analyzed by GC method, the results demostrated that the main constituents of hydrolyzate monosaccharide covers: xylose, glucose, arabinose, galactose, and their contents are 72.38 %, 11.67 %, 5.98 %, 3.47 %, respectively.The hemicellulose hydrolysates was detoxifyed by the combination of Ca(OH)₂, activated carbon, and vacuum concentrating. The results showed that Ca(OH)₂ could remove furfural. The decoloration rate could be achieved with 93.17 % while xylose loss is 8.70 %, when the activated carbon usage is 5 g/L, and recation temperature is 70℃for 30 min at pH 4. Meantime, phenols compunds removal gets to 98%, and when furfural concentration is 0.32 g/L whose removal is 27.27%. For further study, the removal of furfural can reach to 68.73% in vacuum concentration. The yield of xylitol is 12.36% when using Candida tropicalis directly for fermentation. By comparsion, the yield of xylitol gets to 32.75% after Candida tropicalis was domesticated, as their adaptability and fermentation were enhanced.The optimal fermentation conditions were obtained as follows: pH 6.0, temperature 30℃, hydrolysates 50 mL, inoculum amount 10%, and the yield of xylitol could reach to 34.38%. Monosaccharide and xylitol were analyzed by HPLC method, and the results indicates that xylose is converted into xylitol by fermentation process.