Unleashing the capacity of Rhodococcus for converting lignin into lipids.

Bioconversion of bioresources/wastes (e.g., lignin, chemical pulping byproducts) represents a promising approach for developing a bioeconomy to help address growing energy and materials demands. Rhodococcus, a promising microbial strain, utilizes numerous carbon sources to produce lipids, which are precursors for synthesizing biodiesel and aviation fuels. However, compared to chemical conversion, bioconversion involves living cells, which is a more complex system that needs further understanding and upgrading. Various wastes amenable to bioconversion are reviewed herein to highlight the potential of Rhodococci for producing lipid-derived bioproducts. In light of the abundant availability of these substrates, Rhodococcus' metabolic pathways converting them to lipids are analyzed from a "beginning-to-end" view. Based on an in-depth understanding of microbial metabolic routes, genetic modifications of Rhodococcus by employing emerging tools (e.g., multiplex genome editing, biosensors, and genome-scale metabolic models) are presented for promoting the bioconversion. Co-solvent enhanced lignocellulose fractionation (CELF) strategy facilitates the generation of a lignin-derived aromatic stream suitable for the Rhodococcus' utilization. Novel alkali sterilization (AS) and elimination of thermal sterilization (ETS) approaches can significantly enhance the bioaccessibility of lignin and its derived aromatics in aqueous fermentation media, which promotes lipid titer significantly. In order to achieve value-added utilization of lignin, biodiesel and aviation fuel synthesis from lignin and lipids are further discussed. The possible directions for unleashing the capacity of Rhodococcus through synergistically modifying microbial strains, substrates, and fermentation processes are proposed toward a sustainable biological lignin valorization.

Heterostructured Mo and Co-based phosphides as high-performance bifunctional electrocatalysts for overall water splitting.

Transitional metal phosphides are efficient and durable electrocatalysts for water splitting. In this work, Mo-CoP/Co2P/NF heterostructures are reported to exhibit bifunctional electrocatalyst properties in various electrolytes. The Co phosphides were found to be possessing a hydrogenase-like structure in these heterostructures with P as the proton-acceptor site and Co as the hydride-acceptor site, making them highly active during the HER process. Moreover, the electronic structure of Co ions could be modified, or the transfer of electrons could be accelerated due to the different valence states of Mo. Additionally, the Mo centers possessed superior adsorption properties toward hydrogen. Consequently, excellent performance for the electrocatalytic HER was exhibited by the Mo-CoP/Co2P/NF-300 heterostructure with small overpotentials of 86.6 mV and 48 mV at a current density of 10 mA cm-2 in 1.0 M KOH and 0.5 M H2SO4 solutions, respectively. Furthermore, it also exhibited efficient OER activity in an alkaline solution with a low overpotential of 245 mV at 30 mA cm-2. Post-analysis revealed the changes in the surface and the formation of Co oxyhydroxide during the OER process, and the formation of Co-P-O during the HER process. The high HER and OER performances are attributed to these transformations of morphologies and compositions. Consequently, a two-electrode electrolyzer based on Mo-CoP/Co2P/NF-300 required voltages of 1.59 V and 1.703 V at 20 mA cm-2 and 100 mA cm-2, respectively, and maintained long-term stability.

Valorization of homogeneous linear catechyl lignin: opportunities and challenges.

Lignin is the dominant aromatic renewable polymer on earth. Generally, its complex and heterogeneous structure hinders its high-value utilization. Catechyl lignin (C-lignin), a novel lignin discovered in the seed coats of vanilla and several members of Cactaceae, has received increasing attention due to its unique homogeneous linear structure. Obtaining substantial amounts of C-lignin either by gene regulation or effective isolation is essential to advance C-lignin's valorization. Through a fundamental understanding of the biosynthesis process, genetic engineering to promote the accumulation of C-lignin in certain plants was developed to facilitate C-lignin valorization. Various isolation methods were also developed to isolate C-lignin, among which deep eutectic solvents (DESs) treatment is one of the most promising approaches to fractionate C-lignin from biomass materials. Since C-lignin is composed of homogeneous catechyl units, depolymerization to produce catechol monomers demonstrates a promising way for value-added utilization of C-lignin. Reductive catalytic fractionation (RCF) represents another emerging technology for effective depolymerizing C-lignin, leading to a narrow distribution of lignin-derived aromatic products (e.g., propyl and propenyl catechol). Meanwhile, the linear molecular structure predisposes C-lignin as a potential promising feedstock for preparing carbon fiber materials. In this review, the biosynthesis of this unique C-lignin in plants is summarized. C-lignin isolation from plants and various depolymerization approaches to obtaining aromatic products are overviewed with highlights on RCF process. Exploring new application areas based on C-lignin's unique homogeneous linear structure is also discussed with its potential for high-value utilization in the future.

Fabrication and Photocatalytic Activity of Ag3PO4/T-ZnOw Heterostructures.

The Ag3PO4/tetrapod-like ZnO whisker (T-ZnOw) heterostructures were prepared via a simple precipitation method. The obtained heterostructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The photodegradation activity of Ag3PO4/T-ZnOw was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. When the molar ratio of Ag3PO4 to T-ZnOw was 10% (Ag3PO4/T-ZnOw-2), the highest degradation efficiency (92.9%) could be achieved among the heterostructures. The photodegradation rate constant of Ag3PO4/T-ZnOw-2 (0.05179 min-1) was 3.59 times that of T-ZnOw (0.01444 min-1). Besides, the Ag3PO4/T-ZnOw-2 photocatalyst still possessed a degradation efficiency of 77.8% after four successive cycles. The Ag3PO4/T-ZnOw-2 catalyst had much higher photocatalytic activity than pure T-ZnOw and better stability and reusability than pure Ag3PO4. The effect of different scavengers on degradation efficiency was investigated, and the possible photocatalytic mechanism of the Ag3PO4/T-ZnOw photocatalyst was also put forward.

Copper nanocluster-based fluorescence enhanced determination of d-penicillamine.

Taking advantage of the compelling properties of d-penicillamine (d-PA) combined with copper, a method for the sensitive and selective determination of d-PA was established using copper nanocluster (Cu NC)-based fluorescence enhancement. d-PA molecules containing a thiol compound showed a strong tendency to combine with the surface of Cu NCs, causing the re-dispersion of nanoclusters and therefore fluorescence intensity was enhanced. Fluorescence enhancement efficiency of Cu NCs induced by d-PA was linear, with the d-PA concentration varying from 0.6-30 µg ml-1 (R2  = 0.9952) and with a detection limit of 0.54 µg ml-1 . d-PA content in human urine samples was detected with recoveries of 104.8-112.99%. Fluorescence-enhanced determination of d-PA using Cu NCs was established for the first time and this rapid, easy and sensitive method should attract much attention for this application.