School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China.
Pan Asia (Jiangmen) Institute of Biological Engineering and Health, Jiangmen, 529080, China.
Appl Microbiol Biotechnol. 2020 Nov;104(22):9607-9617. doi: 10.1007/s00253-020-10944-x. Epub 2020 Oct 12.
Mycelial adhesion affects cell growth and the production of water-soluble extracellular yellow pigment (EYP) in submerged fermentation with Monascus ruber CGMCC 10910. Two nitrates, NaNO and KNO, were used as nitrogen sources for mitigating mycelial adhesion and improving the production of EYP in this study. The results showed that the adhesion of mycelia in the fermentation broth significantly decreased by adding 5 g/L NaNO, which prevented mycelia from attaching to the inner wall of the Erlenmeyer flask. It was suggested that NaNO reduced the total amount of extracellular polysaccharides, increased extracellular proteins, and decreased the viscosity of the fermentation broth. Scanning electron microscopy (SEM) analysis revealed that the mycelial morphology was shorter and more dispersed and vigorous under NaNO conditions than under the control conditions. The biomass increased by 49.2% and 45.4% with 5 g/L NaNO and 6 g/L KNO treatment, respectively, compared with that of the control, and the maximum production of EYP was 267.1 and 241.8 AU, which increased by 70.0% and 53.9% compared with that of the control, respectively. Simultaneously, the ratios of intracellular yellow pigment to orange pigment increased significantly with 5 g/L of NaNO addition (p < 0.05). Genetic analysis found that the expression levels of the key genes for Monascus pigment biosynthesis were significantly upregulated by NaNO addition (p < 0.05 or p < 0.01). This study provides an effective strategy for the production of water-soluble Monascus yellow pigments.Key Points• Nitrate addition decreased mycelial adhesion and improved cell growth in Monascus pigment fermentation.• The biosynthesis genes of water-soluble extracellular yellow pigment (EYP) were upregulated by nitrate addition.• The mycelial morphology was significantly influenced to enhance EYP biosynthesis with nitrate addition.
菌丝体黏附会影响细胞生长和红曲菌 CGMCC 10910 液体深层发酵中水溶性胞外黄色素（EYP）的产生。本研究使用两种硝酸盐（NaNO₃和 KNO₃）作为氮源，以减轻菌丝体黏附并提高 EYP 的产量。结果表明，添加 5 g/L NaNO₃可显著降低发酵液中菌丝体的黏附，防止菌丝体附着在锥形瓶内壁上。研究表明，NaNO₃减少了胞外多糖的总量，增加了胞外蛋白，降低了发酵液的黏度。扫描电子显微镜（SEM）分析显示，在 NaNO 条件下，菌丝体形态更短、更分散、更旺盛。与对照组相比，添加 5 g/L NaNO 和 6 g/L KNO 分别使生物量增加了 49.2%和 45.4%，最大 EYP 产量分别达到 267.1 和 241.8 AU，分别比对照组提高了 70.0%和 53.9%。同时，添加 5 g/L NaNO 使细胞内黄色素与橙色素的比例显著增加（p<0.05）。遗传分析发现，添加 NaNO 显著上调了 Monascus 色素生物合成的关键基因的表达水平（p<0.05 或 p<0.01）。本研究为水溶性 Monascus 黄色素的生产提供了一种有效的策略。
