Biometabolically Derived Selenium Nanoparticles Armed with Protein Protective Suit toward High-Performance Li-Se Batteries.

Selenium (Se) serves as a burgeoning high-energy-density cathode material in lithium-ion batteries. However, the development of Se cathode is strictly limited by low Se utilization and inferior cycling stability arising from intrinsic volume expansion and notorious shuttle effect. Herein, a microbial metabolism strategy is developed to prepare "functional vesicle-like" Se globules via Bacillus subtilis subsp. from selenite in sewage, in which Se nanoparticles are armed with a natural biological protein membrane with rich nitrogen and phosphorus, achieving the eco-efficient conversion of trash into treasure (selenite, SeO3 2- → Selenium, Se). The appealing-design "functional vesicle-like" Se globules are beneficial to accommodate volume changes of Se in electrochemical reactions, confining polyselenides via chemisorption, and enhancing mechanical strength of electrode by associated bacteria debris, realizing comprehensive utilization of microorganism. By conceptualizing "functional vesicle-like" Se globules, rather than artificial Se-host composites, as cathode for lithium-selenium batteries, it exhibits outstanding cycling stability and improved rate performance. This strategy opens the door to design smart electrode materials with unattainable structure that cannot be achieved by traditional approaches, achieving eco-efficient conversion of pollutants into energy-storage nanomaterials, which will be a promising research field for interdisciplinary of energy, biology, and environment.

Metabolic Engineering of Saccharomyces cerevisiae for High-Level Production of Chlorogenic Acid from Glucose.

Chlorogenic acid (CGA), a major dietary phenolic compound, has been increasingly used in the food and pharmaceutical industries because of its ready availability and extensive biological and pharmacological activities. Traditionally, extraction from plants has been the main approach for the commercial production of CGA. This study reports the first efficient microbial production of CGA by engineering the yeast, Saccharomyces cerevisiae, on a simple mineral medium. First, an optimized de novo biosynthetic pathway for CGA was reconstructed in S. cerevisiae from glucose with a CGA titer of 36.6 ± 2.4 mg/L. Then, a multimodule engineering strategy was employed to improve CGA production: (1) unlocking the shikimate pathway and optimizing carbon distribution; (2) optimizing the l-Phe branch and pathway balancing; and (3) increasing the copy number of CGA pathway genes. The combination of these interventions resulted in an about 6.4-fold improvement of CGA titer up to 234.8 ± 11.1 mg/L in shake flask cultures. CGA titers of 806.8 ± 1.7 mg/L were achieved in a 1 L fed-batch fermenter. This study opens a route to effectively produce CGA from glucose in S. cerevisiae and establishes a platform for the biosynthesis of CGA-derived value-added metabolites.

Recombinant Escherichia coli K5 strain with the deletion of waaR gene decreases the molecular weight of the heparosan capsular polysaccharide.

Heparosan, the capsular polysaccharide of Escherichia coli K5 having a carbohydrate backbone similar to that of heparin, has become a potential precursor for bioengineering heparin. In the heparosan biosynthesis pathway, the gene waaR encoding α-1-, 2- glycosyltransferase catalyze s the third glucosyl residues linking to the oligosaccharide chain. In the present study, a waaR deletion mutant of E. coli K5 was constructed. The mutant showed improvement of capsule polysaccharide yield. It is interesting that the heparosan molecular weight of the mutant is reduced and may become more suitable as a precursor for the production of low molecular weight heparin derived from the wild-type K5 capsular polysaccharide.

Production of a low molecular weight heparin using recombinant glycuronidase [corrected].

The Δ4,5 unsaturated uronate (4-deoxy-α-l-threo-hex-4-eno-pyranosyluronic acid) residue is produced through the depolymerization of heparin, heparosan, and heparan sulfate with heparin lyases. The recovery of unsaturated uronate containing products is necessary to prepare low molecular weight heparin (LMWH) from heparin or heparosan. In this study, the gene of Δ4,5 and Δ4,5(Δ20) unsaturated glycuronidase (EC# 3.2.1.56) from Pedobacter heparinus (formerly Flavobacterium heparinum) was cloned into pMAL-c2x plasmid. Its fusion protein with MBP was expressed in Escherichia coli TB1. After purification, Δ4,5 unsaturated glycuronidase was evaluated. The Δ4,5(Δ20) glycuronidase showed excellent activity on the unsaturated bonds of the different depolymerized products from Hep I, Hep II, and Hep III on heparin, heparosan, and heparan sulfate.

Quantitation of heparosan with heparin lyase III and spectrophotometry.

Heparosan is Escherichia coli K5 capsule polysaccharide, which is the key precursor for preparing bioengineered heparin. A rapid and effective quantitative method for detecting heparosan is important in the large-scale production of heparosan. Heparin lyase III (Hep III) effectively catalyzes the heparosan depolymerization, forming unsaturated disaccharides that are measurable using a spectrophotometer at 232 nm. We report a new method for the quantitative detection of heparosan with heparin lyase III and spectrophotometry that is safer and more specific than the traditional carbazole assay. In an optimized detection system, heparosan at a minimum concentration of 0.60 g/L in fermentation broth can be detected.