Strain screening and fermentation of corn cob hydrolysate for xylitol production

• Main Authors: Wei-Chih Kuo, 郭威志
• Other Authors: Shiuan-yuh Chien
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/00561118928309963812

碩士 === 朝陽科技大學 === 應用化學系碩士班 === 95 === Xylitol, a five carbon sugar alcohol, is one of valuable polyol sweeteners. It can use as a natural food sweetener, a dental caries reducer, and a sugar substitute for diabetics. In the past, xylitol was produced from xylose fermented by suitable microorganisms, but the cost of xylitol is expensive. Therefore, how to develop cheap materials to substitute xylose and maintain the reasonable yield efficiency of xylitol is a necessary research. In this study, Pichia caribbica isolated from soil and Candida guilliermondii collected from BCRC ( Bioresource collection and research center, Taiwan ) to compare the effects of environmental conditions on the productions of xylitol between the two strains and select suitable material to substitute xylose for producing xylitol. The experimental results showed the suitable conditions for P. caribbica and C. guilliermondii to ferment 15% xylose to produce xylitol were 35℃ and 30℃, 50-100 rpm and 100-150 rpm rotary speeds respectively. When the inoculation ratios of P. caribbica and C. guilliermondii suspensions to cultured medium raised from 1% ( v:v ) to 3% , the xylitol yield efficiencies could increase 0.09 g g-1 respectively. When xylose containing medium added with 10-20% ( v:w ) glucose and fermented with P. Caribbica the yield efficiency of xylitol increased 1.5 folds that of without adding glucose. Because the hydrolysate of white corn cob had the highest xylose concentration among the twelve organic materials hydrolyzed with 1% H2SO4, so it was selected for the candidate material of the research. 2.45% xylose was obtained when 50 g L-1 corn cobs was hydrolyzed with 1.5% sulfuric acid under 121℃, 1.1atm and 15 minute condition. After hydrolysis, the hydrolysate concentrated to 4 folds and passed through calcium saturated ion exchange resin to separate xylose from pigment and salt. The result showed when the flow rate of mobile phase was 3 mL min-1 , with loading 1mL each time at 45℃ operation temperature, the separation percentage of xylose could reach 63.25%. After passing through calcium saturated ion exchange the concentrated hydrolysate inoculated with P. caribbica and C. guilliermondii suspension could get 0.39 g g-1 and 0.48 g g-1 yield efficiency respectively.