Oh D K, Kim S Y
Department of Food Science and Technology, Woosuk University, Chonbuk, Korea.
Appl Microbiol Biotechnol. 1998 Oct;50(4):419-25. doi: 10.1007/s002530051314.
Candida tropicalis, a strain isolated from the sludge of a factory manufacturing xylose, produced a high xylitol concentration of 131 g/l from 150 g/l xylose at 45 h in a flask. Above 150 g/l xylose, however, volumetric xylitol production rates decreased because of a lag period in cell growth. In fed-batch culture, the volumetric production rate and xylitol yield from xylose varied substantially with the controlled xylose concentration and were maximum at a controlled xylose concentration of 60 g/l. To increase the xylitol yield from xylose, feeding experiments using different ratios of xylose and glucose were carried out in a fermentor. The maximum xylitol yield from 300 g/l xylose was 91% at a glucose/xylose feeding ratio of 15%, while the maximum volumetric production rate of xylitol was 3.98 g l-1 h-1 at a glucose/xylose feeding ratio of 20%. Xylitol production was found to decrease markedly as its concentration rose above 250 g/l. In order to accumulate xylitol to 250 g/l, 270 g/l xylose was added in total, at a glucose/xylose feeding ratio of 15%. Under these conditions, a final xylitol production of 251 g/l, which corresponded to a yield of 93%, was obtained from 270 g/l xylose in 55 h.
热带假丝酵母是从一家生产木糖的工厂的污泥中分离出的菌株，在摇瓶中于45小时内从150 g/l木糖中产生了131 g/l的高木糖醇浓度。然而，当木糖浓度高于150 g/l时，由于细胞生长的延迟期，木糖醇的体积产率下降。在分批补料培养中，木糖醇的体积产率和木糖转化率随控制的木糖浓度而有很大变化，在控制木糖浓度为60 g/l时达到最大值。为了提高木糖的木糖醇转化率，在发酵罐中进行了使用不同木糖与葡萄糖比例的补料实验。当葡萄糖/木糖补料比例为15%时，300 g/l木糖的最大木糖醇转化率为91%，而当葡萄糖/木糖补料比例为20%时，木糖醇的最大体积产率为3.98 g l-1 h-1。发现当木糖醇浓度升至250 g/l以上时，木糖醇产量显著下降。为了将木糖醇积累至250 g/l，以15%的葡萄糖/木糖补料比例总共添加了270 g/l木糖。在这些条件下，在55小时内从270 g/l木糖中获得了251 g/l的最终木糖醇产量，其转化率为93%。
