Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Faculty of Science and Engineering, Department of Life Science, Setsunan University, 17-8 Ikeda-Nakamachi, Neyagawa, Osaka, 572-8508, Japan.
Sci Rep. 2019 Nov 20;9(1):17147. doi: 10.1038/s41598-019-53597-1.
Alginate is a linear polyuronate in brown macroalgae. It is also a promising marine biopolymer that can be degraded by exo-type alginate lyase into an unsaturated uronate that is non-enzymatically or enzymatically converted to 4-deoxy-L-erythro-5-hexoseulose uronate (DEH). In a bioengineered yeast Saccharomyces cerevisiae (DEH++) strain that utilizes DEH, DEH is not only an important physiological metabolite but also a promising carbon source for biorefinery systems. In this study, we uncovered the essential chemical nature of DEH. In particular, we showed that DEH non-enzymatically reacts with specific amino groups in Tris, ammonium salts [(NH)SO and NHCl], and certain amino acids (e.g., Gly, Ser, Gln, Thr, and Lys) at 30 °C and forms other compounds, one of which we tentatively named DEH-related product-1 (DRP-1). In contrast, Asn, Met, Glu, and Arg were almost inert and Ala, Pro, Leu, Ile, Phe, Val, and Asp, as well as sodium nitrate (NaNO), were inert in the presence of DEH. Some of the above amino acids (Asn, Glu, Ala, Pro, Phe, and Asp) were suitable nitrogen sources for the DEH++ yeast strain, whereas ammonium salts and Ser, Gln, and Thr were poor nitrogen sources owing to their high reactivity to DEH. Nutrient-rich YP medium with 1% (w/v) Yeast extract and 2% (w/v) Tryptone, as well as 10-fold diluted YP medium, could also be effectively used as nitrogen sources. Finally, we identified DRP-1 as a 2-furancarboxylic acid and showed that it has a growth-inhibitory effect on the DEH++ yeast strain. These results show the reactive nature of DEH and suggest a basis for selecting nitrogen sources for use with DEH and alginate in biorefineries. Our results also provide insight into the physiological utilization of DEH. The environmental source of 2-furancarboxylic acid is also discussed.
海藻酸钠是一种存在于褐藻中的线性聚戊糖。它也是一种很有前途的海洋生物聚合物，可通过外切型海藻酸盐裂解酶降解为不饱和糖醛酸，该糖醛酸无需酶或酶促转化为 4-去氧-L-赤-5-己酮糖醛酸（DEH）。在利用 DEH 的生物工程酵母酿酒酵母（DEH++）菌株中，DEH 不仅是一种重要的生理代谢物，而且是生物精炼系统有前途的碳源。在这项研究中，我们揭示了 DEH 的基本化学性质。特别是，我们表明 DEH 可在 30°C 下与 Tris、铵盐[(NH4)2SO4 和 NH4Cl]和某些氨基酸（例如 Gly、Ser、Gln、Thr 和 Lys）中的特定氨基基团非酶促反应，并形成其他化合物，其中一种我们暂定名为 DEH 相关产物-1（DRP-1）。相比之下，Asn、Met、Glu 和 Arg 几乎没有反应性，Ala、Pro、Leu、Ile、Phe、Val 和 Asp 以及硝酸钠（NaNO3）在 DEH 存在下也没有反应性。上述一些氨基酸（Asn、Glu、Ala、Pro、Phe 和 Asp）是 DEH++酵母菌株的合适氮源，而铵盐和 Ser、Gln 和 Thr 是较差的氮源，因为它们与 DEH 反应性高。富含营养的 YP 培养基（1%（w/v）酵母提取物和 2%（w/v）胰蛋白胨）以及 10 倍稀释的 YP 培养基也可有效用作氮源。最后，我们确定 DRP-1 为 2-糠酸，并表明它对 DEH++酵母菌株具有生长抑制作用。这些结果表明 DEH 的反应性，并为生物精炼厂中 DEH 和海藻酸盐的氮源选择提供了依据。我们的结果还提供了对 DEH 生理利用的深入了解。还讨论了 2-糠酸的环境来源。
