PDF(Pubmed)
Abstract：
BACKGROUND: An important step in replacing petrochemical products with sustainable, cost-effective alternatives is the use of feedstocks other than, e.g., pure glucose in the fermentative production of platform chemicals. Ustilaginaceae offer the advantages of a wide substrate spectrum and naturally produce a versatile range of value-added compounds under nitrogen limitation. A promising candidate is the dicarboxylic acid malic acid, which may be applied as an acidulant in the food industry, a chelating agent in pharmaceuticals, or in biobased polymer production. However, fermentable residue streams from the food and agricultural industry with high nitrogen content, e.g., sugar beet molasses, are unsuited for processes with Ustilaginaceae, as they result in low product yields due to high biomass and low product formation.
RESULTS: This study uncovers challenges in evaluating complex feedstock applicability for microbial production processes, highlighting the role of secondary substrate limitations, internal storage molecules, and incomplete assimilation of these substrates. A microliter-scale screening method with online monitoring of microbial respiration was developed using malic acid production with Ustilago trichophora on molasses as an application example. Investigation into nitrogen, phosphate, sulphate, and magnesium limitations on a defined minimal medium demonstrated successful malic acid production under nitrogen and phosphate limitation. Furthermore, a reduction of nitrogen and phosphate in the elemental composition of U. trichophora was revealed under the respective secondary substrate limitation. These adaptive changes in combination with the intricate metabolic response hinder mathematical prediction of product formation and make the presented screening methodology for complex feedstocks imperative. In the next step, the screening was transferred to a molasses-based complex medium. It was determined that the organism assimilated only 25% and 50% of the elemental nitrogen and phosphorus present in molasses, respectively. Due to the overall low content of bioavailable phosphorus in molasses, the replacement of the state-of-the-art nitrogen limitation was shown to increase malic acid production by 65%.
CONCLUSIONS: The identification of phosphate as a superior secondary substrate limitation for enhanced malic acid production opens up new opportunities for the effective utilization of molasses as a more sustainable and cost-effective substrate than, e.g., pure glucose for biobased platform chemical production.
RESULTS: This study uncovers challenges in evaluating complex feedstock applicability for microbial production processes, highlighting the role of secondary substrate limitations, internal storage molecules, and incomplete assimilation of these substrates. A microliter-scale screening method with online monitoring of microbial respiration was developed using malic acid production with Ustilago trichophora on molasses as an application example. Investigation into nitrogen, phosphate, sulphate, and magnesium limitations on a defined minimal medium demonstrated successful malic acid production under nitrogen and phosphate limitation. Furthermore, a reduction of nitrogen and phosphate in the elemental composition of U. trichophora was revealed under the respective secondary substrate limitation. These adaptive changes in combination with the intricate metabolic response hinder mathematical prediction of product formation and make the presented screening methodology for complex feedstocks imperative. In the next step, the screening was transferred to a molasses-based complex medium. It was determined that the organism assimilated only 25% and 50% of the elemental nitrogen and phosphorus present in molasses, respectively. Due to the overall low content of bioavailable phosphorus in molasses, the replacement of the state-of-the-art nitrogen limitation was shown to increase malic acid production by 65%.
CONCLUSIONS: The identification of phosphate as a superior secondary substrate limitation for enhanced malic acid production opens up new opportunities for the effective utilization of molasses as a more sustainable and cost-effective substrate than, e.g., pure glucose for biobased platform chemical production.
摘要：
背景：用可持续的方法取代石化产品的重要一步，具有成本效益的替代品是使用除了，例如，纯葡萄糖在平台化学品的发酵生产中。乌草科提供了广泛的底物谱的优点，并在氮限制下自然产生多种增值化合物。一个有希望的候选者是二羧酸苹果酸，可以用作食品工业中的酸化剂，药物中的螯合剂，或在生物基聚合物生产中。然而,来自食品和农业产业的可发酵残渣流，氮含量高，例如，甜菜糖蜜,不适合乌草科的加工，因为它们由于高生物量和低产物形成而导致低产物产率。
结果：这项研究揭示了在评估微生物生产过程中复杂原料适用性方面的挑战，强调次要底物限制的作用，内部储存分子，和这些底物的不完全同化。以糖蜜上Ustilagotrichophora生产苹果酸为应用实例，开发了一种可在线监测微生物呼吸的微公升筛选方法。氮的调查，磷酸盐,硫酸盐,在确定的基本培养基上的镁限制表明，在氮和磷酸盐限制下成功生产苹果酸。此外，在相应的次要底物限制下，揭示了毛虫的元素组成中氮和磷酸盐的减少。这些适应性变化与复杂的代谢反应相结合，阻碍了产物形成的数学预测，并使提出的复杂原料的筛选方法势在必行。下一步,将筛选转移到基于糖蜜的复合培养基中.确定该生物仅吸收了糖蜜中25％和50％的元素氮和磷，分别。由于糖蜜中生物可利用磷的含量总体较低，最新的氮限制被证明可以使苹果酸的产量增加65%。
结论：将磷酸盐确定为提高苹果酸生产的优异的次要底物限制，为有效利用糖蜜作为更可持续和更具成本效益的底物开辟了新的机会，例如，用于生物基平台化学品生产的纯葡萄糖。
结果：这项研究揭示了在评估微生物生产过程中复杂原料适用性方面的挑战，强调次要底物限制的作用，内部储存分子，和这些底物的不完全同化。以糖蜜上Ustilagotrichophora生产苹果酸为应用实例，开发了一种可在线监测微生物呼吸的微公升筛选方法。氮的调查，磷酸盐,硫酸盐,在确定的基本培养基上的镁限制表明，在氮和磷酸盐限制下成功生产苹果酸。此外，在相应的次要底物限制下，揭示了毛虫的元素组成中氮和磷酸盐的减少。这些适应性变化与复杂的代谢反应相结合，阻碍了产物形成的数学预测，并使提出的复杂原料的筛选方法势在必行。下一步,将筛选转移到基于糖蜜的复合培养基中.确定该生物仅吸收了糖蜜中25％和50％的元素氮和磷，分别。由于糖蜜中生物可利用磷的含量总体较低，最新的氮限制被证明可以使苹果酸的产量增加65%。
结论：将磷酸盐确定为提高苹果酸生产的优异的次要底物限制，为有效利用糖蜜作为更可持续和更具成本效益的底物开辟了新的机会，例如，用于生物基平台化学品生产的纯葡萄糖。
