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, NaNO₃ and KNO₃, 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 NaNO₃, which prevented mycelia from attaching to the inner wall of the Erlenmeyer flask. It was suggested that NaNO₃ 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 NaNO₃ conditions than under the control conditions. The biomass increased by 49.2% and 45.4% with 5 g/L NaNO₃ and 6 g/L KNO₃ treatment, respectively, compared with that of the control, and the maximum production of EYP was 267.1 and 241.8 AU₃₅₀, 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 NaNO₃ addition (p < 0.05). Genetic analysis found that the expression levels of the key genes for Monascus pigment biosynthesis were significantly upregulated by NaNO₃ 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.

在红曲霉CGMCC 10910的深层发酵中，菌丝体的附着力影响细胞生长和水溶性细胞外黄色素（EYP）的产生。两种硝酸盐，NaNO ₃和KNO ₃用作氮源，可减轻菌丝体的附着力并改善细菌的产生。这项研究中的EYP。结果表明，通过添加5 g / L NaNO _3可以显着降低菌丝在发酵液中的粘附，从而防止菌丝附着在锥形瓶的内壁上。有人建议NaNO ₃减少了细胞外多糖的总量，增加了细胞外蛋白质，并降低了发酵液的粘度。扫描电子显微镜（SEM）分析显示，与对照相比，NaNO ₃条件下菌丝体形态更短，更分散，更有活力。生物量增加了49.2％和45.4％用5g / L的NaNO ₃和6g / L KNO ₃处理，分别与对照相比，最大生产EYP的是267.1和241.8 AU ₃₅₀，这增加了与对照组相比分别为70.0％和53.9％。同时，NaNO 5 g / L时，细胞内黄色颜料与橙色颜料的比例显着增加₃添加（p  ＜0.05）。遗传分析发现，添加NaNO ₃显着上调了红曲霉色素生物合成关键基因的表达水平（p  <0.05或p  <0.01）。该研究为生产水溶性红曲黄色颜料提供了有效的策略。

关键点

•添加硝酸盐可降低红曲色素色素发酵中的菌丝体粘附并改善细胞生长。

•硝酸盐的添加会上调水溶性细胞外黄色素（EYP）的生物合成基因。

•加入硝酸盐后，菌丝的形态受到显着影响，以增强EYP的生物合成。