Engineering Yarrowia lipolytica to enhance lipid production from lignocellulosic materials

Background: Yarrowia lipolytica is a common biotechnological chassis for the production of lipids, which are the pre‑ ferred feedstock for the production of fuels and chemicals. To reduce the cost of microbial lipid production, inexpen‑ sive carbon sources must be used, such as lignocellulosic hydrolysates. Unfortunately, lignocellulosic materials often contain toxic compounds and a large amount of xylose, which cannot be used by Y. lipolytica. Results: In this work, we engineered this yeast to efciently use xylose as a carbon source for the production of lipids by overexpressing native genes. We further increased the lipid content by overexpressing heterologous genes to facilitate the conversion of xylose-derived metabolites into lipid precursors. Finally, we showed that these engineered strains were able to grow and produce lipids in a very high yield (lipid content = 67%, titer = 16.5 g/L, yield = 3.44 g/g sugars, productivity 1.85 g/L/h) on a xylose-rich agave bagasse hydrolysate in spite of toxic compounds. Conclusions: This work demonstrates the potential of metabolic engineering to reduce the costs of lipid production from inexpensive substrates as source of fuels and chemicals

Distinct Campylobacter fetus lineages adapted as livestock pathogens and human pathobionts in the intestinal microbiota

Campylobacter fetus is a venereal pathogen of cattle and sheep, and an opportunistic human pathogen. It is often assumed that C. fetus infection occurs in humans as a zoonosis through food chain transmission. Here we show that mammalian C. fetus consists of distinct evolutionary lineages, primarily associated with either human or bovine hosts. We use whole-genome phylogenetics on 182 strains from 17 countries to provide evidence that C. fetus may have originated in humans around 10,500 years ago and may have "jumped" into cattle during the livestock domestication period. We detect C. fetus genomes in 8% of healthy human fecal metagenomes, where the human-associated lineages are the dominant type (78%). Thus, our work suggests that C. fetus is an unappreciated human intestinal pathobiont likely spread by human to human transmission. This genome-based evolutionary framework will facilitate C. fetus epidemiology research and the development of improved molecular diagnostics and prevention schemes for this neglected pathogen

In Situ Oxidation Study of Pt(110) and Its Interaction with CO

WOS: 000298713600054PubMed ID: 22070406Many interesting structures have been observed for O(2)-exposed Pt(110). These structures, along with their stability and reactivity toward CO, provide insights into catalytic processes on open Pt surfaces, which have similarities to Pt nanoparticle catalysts. In this study, we present results from ambient-pressure X-ray photoelectron spectroscopy, high-pressure scanning tunneling microscopy, and density functional theory calculations. At low oxygen pressure, only chemisorbed oxygen is observed on the Pt(110) surface. At higher pressure (0.5 Torr of O(2)), nanometer-sized islands of multilayered alpha-PtO(2)-like surface oxide form along with chemisorbed oxygen. Both chemisorbed oxygen and the surface oxide are removed in the presence of CO, and the rate of disappearance of the surface oxide is dose to that of the chemisorbed oxygen at 270 K. The spectroscopic features of the surface oxide are similar to the oxide observed on Pt nanoparticles of a similar size, which provides us an extra incentive to revisit some single-crystal model catalyst surfaces under elevated pressure using in situ tools.Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]; National Science Foundation of China [20873142, 20923001]; Ministry of Science and Technology of China [2007CB815205]; Korea Research Foundation (KRF); Korean government (MEST) [2009-0068720]; ALSThe Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We thank Dr. Yimin Li for the fruitful discussion. W.-X.L. acknowledges financial support by the National Science Foundation of China (Nos. 20873142 and 20923001), the Ministry of Science and Technology of China (No. 2007CB815205). B.S.M. appreciates the support of the Korea Research Foundation (KRF) grant funded by the Korean government (MEST) (No. 2009-0068720). M.E.G. acknowledges the support of the ALS Postdoctoral Fellowship program