RESUMEN
Engineering synthetic heterotrophy is a key to the efficient bio-based valorization of renewable and waste substrates. Among these, engineering hemicellulosic pentose utilization has been well-explored in Saccharomyces cerevisiae (yeast) over several decades-yet the answer to what makes their utilization inherently recalcitrant remains elusive. Through implementation of a semi-synthetic regulon, we find that harmonizing cellular and engineering objectives are a key to obtaining highest growth rates and yields with minimal metabolic engineering effort. Concurrently, results indicate that "extrinsic" factors-specifically, upstream genes that direct flux of pentoses into central carbon metabolism-are rate-limiting. We also reveal that yeast metabolism is innately highly adaptable to rapid growth on non-native substrates and that systems metabolic engineering (i.e., functional genomics, network modeling, etc.) is largely unnecessary. Overall, this work provides an alternate, novel, holistic (and yet minimalistic) approach based on integrating non-native metabolic genes with a native regulon system.
Asunto(s)
Pentosas , Saccharomyces cerevisiae , Saccharomyces cerevisiae/metabolismo , Pentosas/metabolismo , Ingeniería Metabólica/métodos , FermentaciónRESUMEN
Engineering the utilization of non-native substrates, or synthetic heterotrophy, in proven industrial microbes such as Saccharomyces cerevisiae represents an opportunity to valorize plentiful and renewable sources of carbon and energy as inputs to bioprocesses. We previously demonstrated that activation of the galactose (GAL) regulon, a regulatory structure used by this yeast to coordinate substrate utilization with biomass formation during growth on galactose, during growth on the non-native substrate xylose results in a vastly altered gene expression profile and faster growth compared with constitutive overexpression of the same heterologous catabolic pathway. However, this effort involved the creation of a xylose-inducible variant of Gal3p (Gal3pSyn4.1), the sensor protein of the GAL regulon, preventing this semi-synthetic regulon approach from being easily adapted to additional non-native substrates. Here, we report the construction of a variant Gal3pMC (metabolic coordinator) that exhibits robust GAL regulon activation in the presence of structurally diverse substrates and recapitulates the dynamics of the native system. Multiple molecular modeling studies suggest that Gal3pMC occupies conformational states corresponding to galactose-bound Gal3p in an inducer-independent manner. Using Gal3pMC to test a regulon approach to the assimilation of the non-native lignocellulosic sugars xylose, arabinose, and cellobiose yields higher growth rates and final cell densities when compared with a constitutive overexpression of the same set of catabolic genes. The subsequent demonstration of rapid and complete co-utilization of all three non-native substrates suggests that Gal3pMC-mediated dynamic global gene expression changes by GAL regulon activation may be universally beneficial for engineering synthetic heterotrophy.
Asunto(s)
Proteínas de Saccharomyces cerevisiae , Factores de Transcripción , Factores de Transcripción/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Procesos Heterotróficos , Galactosa/genética , Galactosa/metabolismo , Xilosa/genética , Xilosa/metabolismo , Saccharomyces cerevisiae/metabolismoRESUMEN
Background: In Germany, the number of calls for Emergency Medical Services (EMS) are increasing, while the number of general practitioners and hospitals are decreasing, resulting in a growing demand and workload for emergency physicians and paramedics. Furthermore, an aging population with increasingly complex medical histories, present emergencies in which a more detailed assessment and therapies are urgently needed. Therefore, common EMS systems need to find solutions to handle these problems. Methods: We used a user-focused five-step approach to define a technological solution: Research of current systems, definition of goals and requirements, development of concept, test series and evaluation, evaluation of costs and benefits. Results: Development of a holistic telemedical concept to connect in-hospital clinical emergency physicians and paramedics on the scene, by implementing and connecting systems that are already partially being used in common EMS in Germany. By using live audio and video communication, including vital signs between the two, a system can be established by keeping costs low, affordable and at the same time protecting patient data in line with General Data Protection Regulation. Conclusion: Implementing technologies in a practical specialty like Emergency Medicine with a user-focused approach demonstrates that the hurdle for integration into established routines can improve current processes. Evaluation of costs and usability is a main driver to define success of such concepts and can improve if such systems can be developed to be used in larger networks.