Abstract
BackgroundAs the second most abundant polysaccharide in nature, hemicellulose can be degraded to xylose as the feedstock for bioconversion to fuels and chemicals. To enhance xylose conversion, the engineered Saccharomyces cerevisiae with xylose metabolic pathway is usually adapted with xylose as the carbon source in the laboratory. However, the mechanism under the adaptation phenomena of the engineered strain is still unclear.ResultsIn this study, xylose-utilizing S. cerevisiae was constructed and used for the adaptation study. It was found that xylose consumption rate increased 1.24-fold in the second incubation of the yYST12 strain in synthetic complete-xylose medium compared with the first incubation. The study figured out that it was observed at the single-cell level that the stagnation time for xylose utilization was reduced after adaptation with xylose medium in the microfluidic device. Such transient memory of xylose metabolism after adaptation with xylose medium, named “xylose consumption memory”, was observed in the strains with both xylose isomerase pathway and xylose reductase and xylitol dehydrogenase pathways. In further, the proteomic acetylation of the strains before and after adaptation was investigated, and it was revealed that H4K5 was one of the most differential acetylation sites related to xylose consumption memory of engineered S. cerevisiae. We tested 8 genes encoding acetylase or deacetylase, and it was found that the knockout of the GCN5 and HPA2 encoding acetylases enhanced the xylose consumption memory.ConclusionsThe behavior of xylose consumption memory in engineered S. cerevisiae can be successfully induced with xylose in the adaptation. H4K5Ac and two genes of GCN5 and HPA2 are related to xylose consumption memory of engineered S. cerevisiae during adaptation. This study provides valuable insights into the xylose adaptation of engineered S. cerevisiae.
Highlights
As the second most abundant polysaccharide in nature, hemicellulose can be degraded to xylose as the feedstock for bioconversion to fuels and chemicals
The “xylose consumption memory” behavior of xylose‐utilizing S. cerevisiae The metabolic pathway with xylose reductase and xylitol dehydrogenase was engineered in yYST10 and yYST12, and SQ-2 with the same pathway is a gift from Professor Li-min Cao group at Capital Normal University (Fig. 1A, Table 1)
The microfluidic experiment further confirmed the xylose consumption memory (XCM) behaviors of the xylose-utilizing S. cerevisiae at single-cell level. These results indicated that the rapid adaptation of xylose metabolism for the engineered S. cerevisiae exactly existed under the switching of the media
Summary
As the second most abundant polysaccharide in nature, hemicellulose can be degraded to xylose as the feedstock for bioconversion to fuels and chemicals. How‐ ever, the mechanism under the adaptation phenomena of the engineered strain is still unclear. Lignocellulosic biomass, such as energy crops, aquatic plants, forest biomass, and agricultural residues, is one of the most important renewable sources. The second generation bioethanol had been developed using lignocellulosic biomass to supply liquid fuel for vehicles [3,4,5]. Glucose is a preferred substrate for ethanol production by S. cerevisiae, but xylose generally cannot be effectively converted to ethanol [9]. S. cerevisiae has engineering with xylose pathway to convert xylose to bioethanol [10, 11], and various strategies and genetic modifications have been developed to improve the xylose utilization of S. cerevisiae [12, 13]. The adaptation with xylose medium is still the most efficient approach to improve xylose utilization, but the mechanism of the adaptation is still unclear [14, 15]
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