Advances in Engineering for Xylose Fermentation and Biofuel Production: Balancing Growth, Metabolism, and Defense.

Genetically engineering microorganisms to produce chemicals has changed the industrialized world. The budding yeast is frequently used in industry due to its genetic tractability and unique metabolic capabilities. has been engineered to produce novel compounds from diverse sugars found in lignocellulosic biomass, including pentose sugars, like xylose, not recognized by the organism.

PKA regulatory subunit Bcy1 couples growth, lipid metabolism, and fermentation during anaerobic xylose growth in Saccharomyces cerevisiae.

Organisms have evolved elaborate physiological pathways that regulate growth, proliferation, metabolism, and stress response. These pathways must be properly coordinated to elicit the appropriate response to an ever-changing environment. While individual pathways have been well studied in a variety of model systems, there remains much to uncover about how pathways are integrated to produce systemic changes in a cell, especially in dynamic conditions.

Comparative functional genomics identifies an iron-limited bottleneck in a strain with a cytosolic-localized isobutanol pathway.

Metabolic engineering strategies have been successfully implemented to improve the production of isobutanol, a next-generation biofuel, in . Here, we explore how two of these strategies, pathway re-localization and redox cofactor-balancing, affect the performance and physiology of isobutanol producing strains. We equipped yeast with isobutanol cassettes which had either a mitochondrial or cytosolic localized isobutanol pathway and used either a redox-imbalanced (NADPH-dependent) or redox-balanced (NADH-dependent) ketol-acid reductoisomerase enzyme.

Phosphoproteome Response to Dithiothreitol Reveals Unique Shared Features of Stress Responses.

To cope with sudden changes in the external environment, the budding yeast orchestrates a multifaceted response that spans many levels of physiology. Several studies have interrogated the transcriptome response to endoplasmic reticulum (ER) stress and the role of regulators such as the Ire1 kinase and Hac1 transcription factors. However, less is known about responses to ER stress at other levels of physiology.

PKA and HOG signaling contribute separable roles to anaerobic xylose fermentation in yeast engineered for biofuel production.

Lignocellulosic biomass offers a sustainable source for biofuel production that does not compete with food-based cropping systems. Importantly, two critical bottlenecks prevent economic adoption: many industrially relevant microorganisms cannot ferment pentose sugars prevalent in lignocellulosic medium, leaving a significant amount of carbon unutilized. Furthermore, chemical biomass pretreatment required to release fermentable sugars generates a variety of toxins, which inhibit microbial growth and metabolism, specifically limiting pentose utilization in engineered strains.