Edelmann Holger, Thieme Nils, Ehrenreich Armin, Zverlov Vladimir, Liebl Wolfgang
Chair of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354, Freising, Germany.
Planet A Foods GmbH, Fraunhoferstrasse 11A, 82152, Planegg, Germany.
Biotechnol Biofuels Bioprod. 2024 Nov 30;17(1):139. doi: 10.1186/s13068-024-02590-6.
Acetone-butanol-ethanol (ABE) fermentation by solventogenic clostridia can be harnessed to produce CO emission neutral bio-based 1-butanol, a valuable compound with a broad range of applications, e.g., in industrial production, as a solvent and as a fuel additive or replacement. However, the relatively low butanol titers and high feedstock costs prevent bio-butanol production on an industrial scale. Agricultural side-stream materials, like milling byproducts, are starch-rich, low-cost and produced all year round. They could be suitable substrates for bio-butanol production by ABE fermentation.
The milling byproducts wheat red dog (WRD), rye second flour (RSF), wheat bran (WB), rye bran (RB) and ergot sclerotia-containing rye waste stream (ER) were found to contain between ~ 30 and ~ 85% glucan, most of which was starch based. WRD, RSF and ER had the highest glucan content, while the brans contained significant xylan concentrations. Four strains selected from the collection of solventogenic clostridia available in our group produced > 6 g/L butanol on the majority of these substrates, with Clostridium beijerinckii NCIMB 8052 showing the best ABE production performance when regarding all tested substrates. Toxic ergot sclerotia-containing waste material was found to be a suited substrate for ABE fermentation. Strain NCIMB 8052 exhibited butanol titers of up to 9 g/L on substrate mixtures of WRD plus ER and the highest butanol yield per used sugars. Finally, a semi-continuous ABE fermentation of C. beijerinckii NCIMB 8052 on WRD plus ER could be maintained for 96 h. The volumetric ABE productivity during the continuous phase of fermentation was ~ 0.41 g L h and a total of 37.7 g ABE was produced out of 168.2 g substrate.
Based on their carbohydrate composition, WRD, RSF and ER were the milling byproducts best suited as substrates for bio-butanol production by clostridial ABE fermentation. Importantly, also ergot sclerotia-containing waste materials can be used as substrates, which can help to reduce process costs. The semi-continuous fermentation showed that clostridial ABE fermentation on milling byproducts may represent a suitable avenue for commercial butanol production after further process and/or strain optimization.
产溶剂梭菌进行的丙酮-丁醇-乙醇（ABE）发酵可用于生产二氧化碳排放中和的生物基1-丁醇，这是一种具有广泛应用的有价值化合物，例如在工业生产中用作溶剂、燃料添加剂或替代品。然而，相对较低的丁醇滴度和较高的原料成本阻碍了生物丁醇的工业化生产。农业副产物，如制粉副产品，富含淀粉、成本低且全年生产。它们可能是通过ABE发酵生产生物丁醇的合适底物。
发现制粉副产品小麦麸屑（WRD）、黑麦二级粉（RSF）、麦麸（WB）、黑麦麸（RB）和含麦角菌核的黑麦废物流（ER）含有约30%至约85%的葡聚糖，其中大部分是基于淀粉的。WRD、RSF和ER的葡聚糖含量最高，而麸皮含有大量木聚糖。从我们小组现有的产溶剂梭菌菌株库中选出的四株菌株在这些底物中的大多数上产生了>6 g/L的丁醇，就所有测试底物而言，拜氏梭菌NCIMB 8052表现出最佳的ABE生产性能。发现含麦角菌核的有毒废料是ABE发酵的合适底物。NCIMB 8052菌株在WRD加ER的底物混合物上的丁醇滴度高达9 g/L，且每消耗的糖产生的丁醇产量最高。最后，拜氏梭菌NCIMB 8052在WRD加ER上的半连续ABE发酵可以维持96小时。发酵连续阶段的体积ABE生产率约为0.41 g L⁻¹ h⁻¹，从168.2 g底物中总共产生了37.7 g ABE。
基于其碳水化合物组成，WRD、RSF和ER是最适合作为梭菌ABE发酵生产生物丁醇底物的制粉副产品。重要的是，含麦角菌核的废料也可用作底物，这有助于降低生产成本。半连续发酵表明，经过进一步的工艺和/或菌株优化后，利用制粉副产品进行梭菌ABE发酵可能是商业生产丁醇的合适途径。
