Silva C J, Roberto I C
Department of Biotechnology/FAENQUIL, Rodovia Itajubá-Lorena, Lorena-SP, Brazil.
Lett Appl Microbiol. 2001 Apr;32(4):248-52. doi: 10.1046/j.1472-765x.2001.00899.x.
To evaluate a simple and economical technique to improve xylitol production using concentrated xylose solutions prepared from rice straw hemicellulosic hydrolysate.
Experiments were carried out with rice straw hemicellulosic hydrolysate containing 90 g l-1 xylose, with and without the addition of nutrients, using the yeast Candida guilliermondii previously grown on the hydrolysate (adapted cells) or on semi-defined medium (unadapted cells). By this method, the yield of xylitol increased from 17 g l-1 to 50 g l-1, and xylose consumption increased from 52% to 83%, after 120 h of fermentation. The xylitol production rates were very close to that (0.42 g l-1 h-1) attained in a medium simulating hydrolysate sugars.
Yeast strain adaptation to the hydrolysate showed to be a suitable method to alleviate the inhibitory effects of the toxic compounds. Adapted cells of Candida guilliermondii can efficiently produce xylitol from hydrolysate with high xylose concentrations.
Yeast adaptation helps the bioconversion process in hydrolysate made from lignocellulosic materials. This low-cost technique provides an alternative to the detoxification methods used for removal of inhibitory compounds. In addition, the use of adapted inocula makes it possible to schedule a series of batch cultures so that the whole plant can be operated almost continuously with a concomitant reduction in the overall operation time.
评估一种简单且经济的技术，该技术利用稻草半纤维素水解液制备的浓缩木糖溶液来提高木糖醇产量。
使用含有90 g l-1木糖的稻草半纤维素水解液进行实验，分别添加和不添加营养物质，采用先前在水解液上生长的季也蒙毕赤酵母（适应细胞）或在半合成培养基上生长的酵母（未适应细胞）。通过这种方法，发酵120小时后，木糖醇产量从17 g l-1增加到50 g l-1，木糖消耗量从52%增加到83%。木糖醇的生产速率与模拟水解液糖的培养基中达到的速率（0.42 g l-1 h-1）非常接近。
酵母菌株对水解液的适应被证明是减轻有毒化合物抑制作用的合适方法。季也蒙毕赤酵母的适应细胞能够有效地从高木糖浓度的水解液中生产木糖醇。
酵母适应有助于木质纤维素材料水解液中的生物转化过程。这种低成本技术为去除抑制性化合物的解毒方法提供了一种替代方案。此外，使用适应的接种物使得安排一系列分批培养成为可能，从而使整个工厂几乎可以连续运行，同时减少总操作时间。
