Itaconic acid is a bio-derived platform chemical with uses ranging from polymer synthesis to biofuel production. The efficient conversion of cellulosic waste streams into itaconic acid could thus enable the sustainable production of a variety of substitutes for fossil oil based products. However, the realization of such a process is currently hindered by an expensive conversion of cellulose into fermentable sugars. Here, we present the stepwise development of a fully consolidated bioprocess (CBP), which is capable of directly converting recalcitrant cellulose into itaconic acid without the need for separate cellulose hydrolysis including the application of commercial cellulases. The process is based on a synthetic microbial consortium of the cellulase producer Trichoderma reesei and the itaconic acid producing yeast Ustilago maydis. A method for process monitoring was developed to estimate cellulose consumption, itaconic acid formation as well as the actual itaconic acid production yield online during co-cultivation. The efficiency of the process was compared to a simultaneous saccharification and fermentation setup (SSF). Because of the additional substrate consumption of T. reesei in the CBP, the itaconic acid yield was significantly lower in the CBP than in the SSF. In order to increase yield and productivity of itaconic acid in the CBP, the population dynamics was manipulated by varying the inoculation delay between T. reesei and U. maydis. Surprisingly, neither inoculation delay nor inoculation density significantly affected the population development or the CBP performance. Instead, the substrate availability was the most important parameter. U. maydis was only able to grow and to produce itaconic acid when the cellulose concentration and thus, the sugar supply rate, was high. Finally, the metabolic processes during fed-batch CBP were analyzed in depth by online respiration measurements. Thereby, substrate availability was again identified as key factor also controlling itaconic acid yield. In summary, an itaconic acid titer of 34 g/L with a total productivity of up to 0.07 g/L/h and a yield of 0.16 g/g could be reached during fed-batch cultivation. This study demonstrates the feasibility of consortium-based CBP for itaconic acid production and also lays the fundamentals for the development and improvement of similar microbial consortia for cellulose-based organic acid production.

中文翻译：

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通过里氏木霉和玉米til的共培养将纤维素生物处理为衣康酸

衣康酸是一种生物衍生的平台化学品，用途从聚合物合成到生物燃料生产。因此，将纤维素废物流有效转化为衣康酸可实现可持续生产多种替代矿物油的产品。但是，目前这种方法的实现由于纤维素向可发酵糖的昂贵转化而受到阻碍。在这里，我们介绍了逐步整合的生物过程（CBP）的逐步开发，该过程能够将难降解的纤维素直接转化为衣康酸，而无需单独的纤维素水解，包括应用商业纤维素酶。该方法基于纤维素酶生产者里氏木霉和生产衣康酸的酵母Ustilago maydis的合成微生物联合体。开发了一种过程监控方法，以估计共培养期间在线的纤维素消耗量，衣康酸形成以及实际衣康酸产量。将该过程的效率与同时糖化和发酵装置（SSF）进行了比较。由于CBP中里氏木霉的额外底物消耗，CBP中的衣康酸收率明显低于SSF。为了提高衣康酸中衣康酸的产量和生产率，通过改变里氏木霉和美里氏木霉之间的接种延迟来控制种群动态。出人意料的是，接种延迟和接种密度均未显着影响种群发育或CBP表现。相反，衬底的可用性是最重要的参数。。maydis仅在纤维素浓度（因此糖供应率）很高时才能生长并产生衣康酸。最后，通过在线呼吸测量对补料分批CBP期间的代谢过程进行了深入分析。因此，再次将底物可用性确定为也是控制衣康酸产率的关键因素。总之，在分批分批培养过程中，衣康酸效价为34 g / L，总生产率高达0.07 g / L / h，产量为0.16 g / g。这项研究证明了基于团聚的CBP在衣康酸生产中的可行性，并且为开发和改进用于纤维素基有机酸的类似微生物团聚奠定了基础。最后，通过在线呼吸测量对补料分批CBP期间的代谢过程进行了深入分析。因此，再次将底物可用性确定为也是控制衣康酸产率的关键因素。总之，在分批分批培养过程中，衣康酸效价为34 g / L，总生产率高达0.07 g / L / h，产量为0.16 g / g。这项研究证明了基于团聚的CBP在衣康酸生产中的可行性，并且为开发和改进用于纤维素基有机酸的类似微生物团聚奠定了基础。最后，通过在线呼吸测量对补料分批CBP期间的代谢过程进行了深入分析。因此，再次将底物可用性确定为也是控制衣康酸产率的关键因素。总之，在分批分批培养过程中，衣康酸效价为34 g / L，总生产率高达0.07 g / L / h，产量为0.16 g / g。这项研究证明了基于团聚的CBP在衣康酸生产中的可行性，并且为开发和改进用于纤维素基有机酸的类似微生物团聚奠定了基础。分批分批培养的衣康酸效价为34 g / L，总生产率高达0.07 g / L / h，产量为0.16 g / g。这项研究证明了基于团聚的CBP在衣康酸生产中的可行性，并且为开发和改进用于纤维素基有机酸的类似微生物团聚奠定了基础。分批分批培养的衣康酸效价为34 g / L，总生产率高达0.07 g / L / h，产量为0.16 g / g。这项研究证明了基于团聚的CBP在衣康酸生产中的可行性，并且为开发和改进用于纤维素基有机酸的类似微生物团聚奠定了基础。