Diano A, Bekker-Jensen S, Dynesen J, Nielsen J
DTU, Biocentrum, Center for Microbial Biotechnology, Lyngby, Denmark.
Biotechnol Bioeng. 2006 Aug 5;94(5):899-908. doi: 10.1002/bit.20915.
Polyol production has been studied in Aspergillus niger under different conditions. Fermentations have been run using high concentration of glucose or xylose as carbon source and ammonium or nitrate as nitrogen source. The growth of biomass, as freely dispersed hyphae, led to an increase of medium viscosity and hereby a decrease in mass transfer, especially oxygen transfer. The consequence was a decrease in DOT and the occurrence of a switch between fully aerobic conditions and oxygen-limited conditions. Metabolite quantification showed that polyols were the main metabolic products formed and represented up to 22% of the carbon consumed in oxygen-limited conditions. The polyol concentration and the polyol pattern depended strongly on the environmental conditions. This is due to a complex regulation of polyol production and to the fact that each polyol can fulfill different functions. In this study, erythritol, xylitol, and arabitol were produced as carbon storage compounds when the flux through the PP pathway exceeded the need in ribulose-5-phosphate for the biomass synthesis. Glycerol, erythritol, and xylitol seem to be involved in osmoregulation. Mannitol was produced when the catabolic reduction of charge was high. Its production involves the enzyme NAD-dependent mannitol-1-phosphate dehydrogenase and seems to be the main cytosolic route for the NADH reoxidation during oxygen limitation.
已在不同条件下对黑曲霉中的多元醇生成进行了研究。使用高浓度葡萄糖或木糖作为碳源，铵或硝酸盐作为氮源进行发酵。作为自由分散菌丝的生物质生长导致培养基粘度增加，从而传质减少，尤其是氧传递减少。结果是溶解氧（DOT）降低，并且出现了从完全好氧条件到氧限制条件的转变。代谢物定量显示，多元醇是形成的主要代谢产物，在氧限制条件下占消耗碳的22%。多元醇浓度和多元醇模式强烈依赖于环境条件。这是由于多元醇生成的复杂调节以及每个多元醇可以发挥不同功能这一事实。在本研究中，当通过磷酸戊糖途径的通量超过生物质合成中对5-磷酸核酮糖的需求时，赤藓糖醇、木糖醇和阿拉伯糖醇作为碳储存化合物产生。甘油、赤藓糖醇和木糖醇似乎参与渗透调节。当分解代谢电荷降低较高时产生甘露醇。其产生涉及依赖NAD的甘露醇-1-磷酸脱氢酶，并且似乎是氧限制期间NADH再氧化的主要胞质途径。
