Rational Engineering of Escherichia coli for High-Level Production of Riboflavin

Riboflavin is widely used as a food additive. Here, multiple strategies were used to increase riboflavin production in Escherichia coli LS31T. First, purR deletion and co-overexpression of fbp, purF, prs, gmk, and ndk genes resulted in an increase of 18.6% in riboflavin titer (reaching 729.7 mg/L). Second, optimization of reduced nicotinamide adenine dinucleotide phosphate/nicotinamide adenine dinucleotide ratio and respiratory chain activity in LS31T increased the titer up to 1020.2 mg/L. Third, the expression level of the guaC gene in LS31T was downregulated by ribosome binding site replacement, and the riboflavin production was increased by 10.6% to 658.5 mg/L. Then, all the favorable modifications were integrated together, and the resulting strain LS72T produced 1339 mg/L of riboflavin. Moreover, the riboflavin titer of LS72T reached 21 g/L in fed-batch cultivation, with a yield of 110 mg riboflavin/g glucose. To our knowledge, both the riboflavin titer and yield obtained in fed-batch fermentation are the highest ones among all the rationally engineered strains

A Stretchable and Sweat-Adhesive 3D Graphene Eutectogel Electrode for EMG Monitoring

Epidermal electrodes play an essential role in accurately capturing electrophysiological signals, which are critical for human health monitoring and human–computer interactions. However, these electrodes face challenges such as the inability to maintain long-term adhesion and limited adaptability to skin deformation, which hinder their sustained and repeated use. In this work, we developed a stretchable and sweat-adhesive epidermal electrode for accurate recording of electromyography (EMG) signals. This electrode is based on the chemical vapor deposition (CVD) of graphene foam and eutectogel. This copolymer exhibits excellent tensile properties (500–600%), sweat adhesion (19 kPa), and low impedance (99 Ω). It provides both structural support and an interfacial conductive medium for the graphene foam, effectively reducing contact impedance with skin. This stretchable and sweat-adhesive epidermal electrode presents an interesting scheme for the preparation of wearable devices

Selective Characterization of Olefins by Paternò–Büchi Reaction with Ultrahigh Resolution Mass Spectrometry

Petroleum olefins play important roles in various secondary processing procedures and are important feedstocks for the modern organic chemical industry. It is quite challenging to analyze petroleum olefins beyond the gas chromatography (GC)-able range using mass spectrometry (MS) due to the difficulty of soft ionization and the matrix complexity. In this work, a Paternò–Büchi (PB) reaction combined with atmospheric pressure chemical ionization and ultrahigh resolution mass spectrometry (APCI–UHRMS) was developed for selective analysis of olefins. Through the PB reaction, CC bonds were transformed into four-membered rings of oxetane with improved polarity so that soft ionization of olefins could be achieved. The systematic optimization of PB reaction conditions, as well as MS ionization conditions, ensured a high reaction yield and a satisfied MS response. Furthermore, a sound scheme was set up to discriminate the coexisting unsaturated alkanes in complex petroleum, including linear olefins, nonlinear olefins, cycloalkanes, and aromatics, making use of their different behaviors during the PB reaction and chemical ionization. The developed strategy was successfully applied to the analysis of olefins in fluid catalytic cracking oil slurry, a complex heavy oil sample. This method extended the characterization of petroleum olefins from lower to higher with high efficiency and selectivity to provide a comprehensive molecular library for heavy petroleum samples and process optimization