Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Ghent Universitygrid.5342.0, Gent, Belgium.
Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium.
Appl Environ Microbiol. 2022 Nov 22;88(22):e0118822. doi: 10.1128/aem.01188-22. Epub 2022 Oct 26.
With industrial agriculture increasingly challenging our ecological limits, alternative food production routes such as microbial protein (MP) production are receiving renewed interest. Among the multiple substrates so far evaluated for MP production, renewable bioethanol (EtOH) is still underexplored. Therefore, the present study investigated the cultivation of five microorganisms (2 bacteria, 3 yeasts) under carbon (C), nitrogen (N), and dual C-N-limiting conditions (molar C/N ratios of 5, 60, and 20, respectively) to evaluate the production (specific growth rate, protein and biomass yield, production cost) as well as the nutritional characteristics (protein and carbohydrate content, amino acid [AA] profile) of MP production from bioethanol. Under C-limiting conditions, all the selected microorganisms showed a favorable AA profile for human nutrition (average AA score of 1.5 or higher), with a negative correlation between protein content and growth rate. Maximal biomass yields were achieved under conditions where no extracellular acetate was produced. Cyberlindnera saturnus and Wickerhamomyces anomalus displayed remarkably high biomass yields (0.40 to 0.82 g cell dry weight [CDW]/g EtOH), which was reflected in the lowest estimated biomass production costs when cultivated with a C/N ratio of 20. Finally, when the production cost was evaluated on a protein basis, Corynebacterium glutamicum grown under C-limiting conditions showed the most promising economic outlook. The global protein demand is rapidly increasing at rates that cannot be sustained, with projections showing 78% increased global protein needs by 2050 (361 compared to 202 million ton/year in 2017). In the absence of dedicated mitigation strategies, the environmental effects of our current food production system (relying on agriculture) are expected to surpass the planetary boundaries-the safe operating space for humanity-by 2050. Here, we illustrate the potential of bioethanol-renewable ethanol produced from side streams-as a main resource for the production of microbial protein, a radically different food production strategy in comparison to traditional agriculture, with the potential to be more sustainable. This study unravels the kinetic, productive, and nutritional potential for microbial protein production from bioethanol using the bacteria Methylorubrum extorquens and Corynebacterium glutamicum and the yeasts Cyberlindnera saturnus, and Metschnikowia pulcherrima, setting the scene for microbial protein production from renewable ethanol.
随着工业农业日益挑战我们的生态极限，替代食物生产途径，如微生物蛋白（MP）生产，正重新受到关注。在迄今为止评估的多种生产 MP 的底物中，可再生生物乙醇（EtOH）仍未得到充分探索。因此，本研究在碳（C）、氮（N）和双 C-N 限制条件下（摩尔比分别为 5、60 和 20）培养了五种微生物（2 种细菌，3 种酵母），以评估 MP 从生物乙醇生产的生产（比生长速率、蛋白质和生物量产量、生产成本）以及营养特性（蛋白质和碳水化合物含量、氨基酸 [AA] 谱）。在 C 限制条件下，所有选定的微生物都表现出有利于人类营养的 AA 谱（平均 AA 评分 1.5 或更高），蛋白质含量与生长速率呈负相关。在没有细胞外乙酸产生的情况下，实现了最大的生物量产量。Cyberlindnera saturnus 和 Wickerhamomyces anomalus 表现出极高的生物量产量（0.40 至 0.82g 细胞干重 [CDW]/g EtOH），这反映在以 20 的 C/N 比培养时估计的最低生物质生产成本。最后，当以蛋白质为基础评估生产成本时，在 C 限制条件下生长的谷氨酸棒杆菌显示出最有希望的经济前景。全球蛋白质需求正以不可持续的速度迅速增长，预计到 2050 年，全球蛋白质需求将增加 78%（2017 年为 361 万吨/年，202 万吨/年）。在没有专门的缓解策略的情况下，我们目前的粮食生产系统（依赖农业）的环境影响预计将在 2050 年前超过地球的界限——人类的安全运行空间。在这里，我们展示了生物乙醇的潜力——可再生乙醇来自副产物——作为微生物蛋白生产的主要资源，与传统农业相比，这是一种截然不同的食物生产策略，具有更大的可持续性。本研究使用细菌 Methylorubrum extorquens 和 Corynebacterium glutamicum 以及酵母 Cyberlindnera saturnus 和 Metschnikowia pulcherrima，从生物乙醇中生产微生物蛋白的动力学、生产性和营养潜力，为微生物蛋白从可再生乙醇生产奠定了基础。
