Recent advances of metal active sites in photocatalytic CO2 reduction.

Photocatalytic CO2 reduction captures solar energy to convert CO2 into hydrocarbon fuels, thus shifting the dependence on rapidly depleting fossil fuels. Among the various proposed photocatalysts, systems containing metal active sites (MASs) possess obvious advantages, such as effective photogenerated carrier separation, suitable adsorption and activation of intermediates, and achievable C-C coupling to generate multi-carbon (C2+) products. The present review aims to summarize the typical photocatalytic materials with MAS, highlighting the critical role of different formulations of MAS in CO2 photoreduction, especially for C2+ product generation. State-of-the-art progress in the characterization and theoretical calculations for MAS-containing photocatalysts is also emphasized. Finally, the challenges and prospects of catalytic systems involving MAS for solar-driven CO2 conversion are outlined, providing inspiration for the future design of materials for efficient photocatalytic energy conversion.

Analysis of lncRNA-related studies of ivermectin-sensitive and -resistant strains of Haemonchus contortus.

In this study, 858 novel long non-coding RNAs (lncRNAs) were predicted as sensitive and resistant strains of Haemonchus contortus to ivermectin. These lncRNAs underwent bioinformatic analysis. In total, 205 lncRNAs significantly differed using log2 (difference multiplicity) > 1 or log2 (difference multiplicity) < - 1 and FDR < 0.05 as the threshold for significant difference analysis. We selected five lncRNAs based on significant differences in expression, cis-regulation, and their association with the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. These expressions of lncRNAs, namely MSTRG.12610.1, MSTRG.8169.1, MSTRG.6355.1, MSTRG.980.1, and MSTRG.9045.1, were significantly downregulated. These findings were consistent with the results of transcriptomic sequencing. We further investigated the relative expression of target gene mRNAs and the regulation of mRNA and miRNA, starting with lncRNA cis-regulation of mRNA, and constructed a lncRNA-mRNA-miRNA network regulation. After a series of statistical analyses, we finally screened out UGT8, Unc-116, Fer-related kinase-1, GGPP synthase 1, and sart3, which may be involved in developing drug resistance under the regulation of their corresponding lncRNAs. The findings of this study provide a novel direction for future studies on drug resistance targets.

A review of emerging membrane-based microalgal-bacterial processes for wastewater treatment: Process configurations, biological and membrane performance, and perspectives.

Microalgal-bacterial (MB) consortia create an excellent eco-system for simultaneous COD/BOD and nutrients (N and P) removals in a single step with significant reduction in or complete elimination of aeration and carbonation in the biological wastewater treatment processes. The integration of membrane separation technology with the MB processes has created a new paradigm for research and development. This paper focuses on a comprehensive and critical literature review of recent advances in these emerging processes. Novel membrane process configurations and process conditions affecting the biological performance of these novel systems have been systematically reviewed and discussed. Membrane fouling issues and control of MB biofilm formation and thickness associated with these emerging suspended growth or immobilized biofilm processes are addressed and discussed. The research gaps, challenges, outlooks of these emerging processes are identified and discussed in-depth. The findings from the literature suggest that the membrane-based MB processes are advanced biotechnologies with a significant reduction in energy consumption and process simplification and high process efficiency that are not achievable with current technologies in wastewater treatment. There are endless opportunities for research and development of these novel and emerging membrane-based MB processes.

Autophagy mediated degradation of MITA/TBK1/IRF3 by a hnRNP family member attenuates interferon production in fish.

HnRNP A/B belongs to the heterogeneous nuclear ribonucleoprotein (hnRNP) family and plays an important role in regulating viral protein translation and genome replication. Here, we found that overexpression of hnRNP A/B promoted spring viremia of carp virus (SVCV) and cyprinid herpesvirus 3 (CyHV3) replication. Further, hnRNP A/B was shown to act as a negative regulator of type I interferon (IFN) response. Mechanistically, hnRNP A/B interacted with MITA, TBK1 and IRF3 to initiate their degradation. In addition, hnRNP A/B bound to the kinase domain of TBK1, the C terminal domain of MITA and IAD domain of IRF3, and the RRM1 domain of hnRNP A/B bound to TBK1, RRM2 domain bound to IRF3 and MITA. Our study provides novel insights into the functions of hnRNP A/B in regulating host antiviral response.

Transcriptome reveals the roles and potential mechanisms of lncRNAs in the regulation of albendazole resistance in Haemonchus contortus.

BACKGROUND: Haemonchus contortus (H. contortus) is the most common parasitic nematode in ruminants and is prevalent worldwide. H. contortus resistance to albendazole (ABZ) hinders the efficacy of anthelmintic drugs, but little is known about the molecular mechanisms that regulate this of drug resistance. Recent research has demonstrated that long noncoding RNAs (lncRNAs) can exert significant influence as pivotal regulators of the emergence of drug resistance. RESULTS: In this study, transcriptome sequencing was conducted on both albendazole-sensitive (ABZ-sensitive) and albendazole-resistant (ABZ-resistant) H. contortus strains, with three biological replicates for each group. The analysis of lncRNA in the transcriptomic data revealed that there were 276 differentially expressed lncRNA (DElncRNA) between strains with ABZ-sensitive and ABZ-resistant according to the criteria of |log2Foldchange|≥ 1 and FDR < 0.05. Notably, MSTRG.12969.2 and MSTRG.9827.1 exhibited the most significant upregulation and downregulation, respectively, in the resistant strains. The potential roles of the DElncRNAs included catalytic activity, stimulus response, regulation of drug metabolism, and modulation of the immune response. Moreover, we investigated the interactions between DElncRNAs and other RNAs, specifically MSTRG.12741.1, MSTRG.11848.1, MSTRG.5895.1, and MSTRG.14070.1, involved in regulating drug stimulation through cis/trans/antisense/lncRNA‒miRNA-mRNA interaction networks. This regulation leads to a decrease (or increase) in the expression of relevant genes, consequently enhancing the resistance of H. contortus to albendazole. Furthermore, through comprehensive analysis of competitive endogenous RNAs (ceRNAs) involved in drug resistance-related pathways, such as the mTOR signalling pathway and ABC transporter signalling pathway, the relevance of the MSTRG.2499.1-novel-m0062-3p-HCON_00099610 interaction was identified to mainly involve the regulation of catalytic activity, metabolism, ubiquitination and transcriptional regulation of gene promoters. Additionally, quantitative real-time polymerase chain reaction (qRT-PCR) validation indicated that the transcription profiles of six DElncRNAs and six DEmRNAs were consistent with those obtained by RNA-seq. CONCLUSIONS: The results of the present study allowed us to better understand the changes in the lncRNA expression profile of ABZ-resistant H. contortus. In total, these results suggest that the lncRNAs MSTRG.963.1, MSTRG.12741.1, MSTRG.11848.1 and MSTRG.2499.1 play important roles in the development of ABZ resistance and can serve as promising biomarkers for further study.

Satisfactory degradation of tetracycline by a pH-universal CoFe-LDH/MoS2 heterojunction catalyst in Fenton process.

Fenton or Fenton-like reactions have been widely used in various fields, including solar energy conversion to generate hydroxyl radicals, environmental remediation, biology, and life science. However, the slow Fe3+/Fe2+ cycle and narrow applicable pH range still present significant challenges. Here, a heterostructured CoFe-layered double hydroxide/MoS2 nanocomposite (CoFe-LDH/MoS2) was prepared via simple electrostatic interactions. The heterostructure establishes a robust interfacial contact, leading to an abundance of exposed Mo6+ sites. Consequently, the developed CoFe-LDH/MoS2+H2O2 system exhibited superior performance in the degradation of tetracycline (>85%) within 60 min across a wide pH range from acidic to basic. Moreover, the CoFe-LDH/MoS2 heterojunction catalysts exhibited exceptional resistance to common anions and efficiently degraded various organic pollutants. The mechanism study verified that the CoFe-LDH/MoS2 had high efficiency in producing 1O2 and ‧OH to degrade various organic pollutants. The present study will serve as a foundation for creating efficient catalyst systems for related environmental remediation.

Carbohydrate-binding modules enhance H2O2 tolerance by promoting lytic polysaccharide monooxygenase active site H2O2 consumption.

Lytic polysaccharide monooxygenases (LPMOs) oxidatively depolymerize recalcitrant polysaccharides, which is important for biomass conversion. The catalytic domains of many LPMOs are linked to carbohydrate-binding modules (CBMs) through flexible linkers, but the function of these CBMs in LPMO catalysis is not well understood. In this study, we utilized MtLPMO9L and MtLPMO9G derived from Myceliophthora thermophila to investigate the impact of CBMs on LPMO activity, with particular emphasis on their influence on H2O2 tolerance. Using truncated forms of MtLPMO9G generated by removing the CBM, we found reduced substrate binding affinity and enzymatic activity. Conversely, when the CBM was fused to the C terminus of the single-domain MtLPMO9L to create MtLPMO9L-CBM, we observed a substantial improvement in substrate binding affinity, enzymatic activity, and notably, H2O2 tolerance. Furthermore, molecular dynamics simulations confirmed that the CBM fusion enhances the proximity of the active site to the substrate, thereby promoting multilocal cleavage and impacting the exposure of the copper active site to H2O2. Importantly, the fusion of CBM resulted in more efficient consumption of H2O2 by LPMO, leading to improved enzymatic activity and reduced auto-oxidative damage of the copper active center.

Tandem Synergistic Effect of Cu-In Dual Sites Confined on the Edge of Monolayer CuInP2 S6 toward Selective Photoreduction of CO2 into Multi-Carbon Solar Fuels.

One-unit-cell, single-crystal, hexagonal CuInP2 S6 atomically thin sheets of≈0.81 nm in thickness was successfully synthesized for photocatalytic reduction of CO2 . Exciting ethene (C2 H4 ) as the main product was dominantly generated with the yield-based selectivity reaching ≈56.4 %, and the electron-based selectivity as high as ≈74.6 %. The tandem synergistic effect of charge-enriched Cu-In dual sites confined on the lateral edge of the CuInP2 S6 monolayer (ML) is mainly responsible for efficient conversion and high selectivity of the C2 H4 product as the basal surface site of the ML, exposing S atoms, can not derive the CO2 photoreduction due to the high energy barrier for the proton-coupled electron transfer of CO2 into *COOH. The marginal In site of the ML preeminently targets CO2 conversion to *CO under light illumination, and the *CO then migrates to the neighbor Cu sites for the subsequent C-C coupling reaction into C2 H4 with thermodynamic and kinetic feasibility. Moreover, ultrathin structure of the ML also allows to shorten the transfer distance of charge carriers from the interior onto the surface, thus inhibiting electron-hole recombination and enabling more electrons to survive and accumulate on the exposed active sites for CO2 reduction.

PGC-1α affects cochlear pericytes migration in noise-exposed mice.

OBJECTIVE: The study aimed to observe the effects of noise exposure on the pericytes of the cochlear stria vascularis (SV) in mice and to investigate its molecular mechanism. METHOD: Male C57BL/6J mice aged 6-8 weeks were used as the subjects. Auditory Brainstem Response (ABR) was used to assess hearing loss. Hematoxylin and Eosin (HE) staining was conducted to observe morphological alterations in the SV. Immunofluorescence combined with transmission electron microscopy (TEM) was used to scrutinize changes in pericytes following acoustic injury. Western blotting (WB) was used to assess the expression variations of the migration-related protein Osteopontin (OPN). Evans Blue assay was performed to evaluate the permeability of the blood labyrinth barrier (BLB). 4-Hydroxynonenal (4-HNE) staining, in conjunction with measurements of Superoxide Dismutase (SOD), Malondialdehyde (MDA), and Catalase (CAT) content, was used to ascertain whether oxidative stress injury occurred in the SV. WB, combined with immunofluorescence, was used to examine alterations in the expression of proliferator-activated receptor-gamma coactivator 1α (PGC-1α) in the SV and pericytes. RESULTS: Noise exposure resulted in permanent hearing loss in C57BL/6J mice, accompanied by SV swelling, migration of pericytes from their vascular attachments, BLB leakage, elevated oxidative stress levels in the SV, and reduced expression of PGC-1α on both the SV and migrating pericytes. CONCLUSION: Noise exposure may potentially increase oxidative stress levels in the SV, downregulate the expression levels of PGC-1α, promote pericytes migration, and subsequently lead to an elevation in BLB permeability.

[Development progress of stationary phase for supercritical fluid chromatography and related application in natural products].

Supercritical fluid chromatography (SFC) is an environment-friendly and efficient column chromatography technology that was developed to expand the application range of high performance liquid chromatography (HPLC) using a supercritical fluid as the mobile phase. A supercritical fluid has a temperature and pressure that are above the critical values as well as relatively dynamic characteristics that are between those of a gas and liquid. Supercritical fluids combine the advantages of high solubility and diffusion, as their diffusion and viscosity coefficients are equivalent to those of a gas, while maintaining a density that is comparable with that of a liquid. Owing to the remarkable compressibility of supercritical fluids, analyte retention in SFC is significantly influenced by the density of the mobile phase. Thus, the column temperature and back pressure are crucial variables that regulate analyte retention in SFC. Increasing the back pressure can increase the density and solubility of the mobile phase, leading to reductions in retention time. The column temperature can affect selectivity and retention, and the degree to which different analytes are affected by this property varies. On the one hand, increasing the temperature reduces the density of the mobile phase, thereby extending the retention time of the analytes; on the other hand, it can also increase the energy of molecules, leading to a shorter retention time of the analyte on the stationary phase. CO2, the most widely employed supercritical fluid to date, presents moderate critical conditions and, more importantly, is miscible with a variety of polar organic solvents, including small quantities of water. In comparison with the mobile phases used in normal-phase liquid chromatography (NPLC) and reversed-phase liquid chromatography (RPLC), the mobile phase for SFC has a polarity that can be extended over a wide range on account of its extensive miscibility. The compatibility of the mobile phase determines the diversity of the stationary phase. Nearly all stationary phases for HPLC, including the nonpolar stationary phases commonly used for RPLC and the polar stationary phases commonly used for NPLC, can be applied to SFC. Because all stationary phases can use the same mobile-phase composition, chromatographic columns with completely different polarities can be employed in SFC. The selectivity of SFC has been effectively expanded, and the technique can be used for the separation of diverse analytes ranging from lipid compounds to polar compounds such as flavonoids, saponins, and peptides. The choice of stationary phase has a great impact on the separation effect of analytes in SFC. As new stationary phases for HPLC are constantly investigated, specialized stationary phases for SFC have also been continuously developed. Researchers have discovered that polar stationary phases containing nitrogen heterocycles such as 2-EP and PIC are highly suitable for SFC because they can effectively manage the peak shape of alkaline compounds and provide good selectivity in separating acidic and neutral compounds.The development of various stationary phases has promoted the applications of SFC in numerous fields such as pharmaceuticals, food production, environmental protection, and natural products. In particular, natural products have specific active skeletons, multiple active groups, and excellent biological activity; hence, these materials can provide many new opportunities for the discovery of novel drugs. According to reports, compounds related to natural products account for 80% of all commercial drugs. However, natural products are among the most challenging compounds to separate because of their complex composition and low concentration of active ingredients. Thus, superior chromatographic methods are required to enable the qualitative and quantitative analysis of natural products. Thanks to technological improvements and a good theoretical framework, the benefits of SFC are gradually becoming more apparent, and its use in separating natural products is expanding. Indeed, in the past 50 years, SFC has developed into a widely used and efficient separation technology. This article provides a brief overview of the characteristics, advantages, and development process of SFC; reviews the available SFC stationary phases and their applications in natural products over the last decade; and discusses prospects on the future development of SFC.

DDX5 inhibits type I IFN production by promoting degradation of TBK1 and disrupting formation of TBK1 - TRAF3 complex.

DExD/H-box helicase (DDX) 5 belongs to the DExD/H-box helicase family. DDX family members play differential roles in the regulation of innate antiviral immune response. However, whether DDX5 is involved in antiviral immunity remains unclear. In this study, we found that DDX5 serves as a negative regulator of type I interferon (IFN) response. Overexpression of DDX5 inhibited IFN production induced by Spring viremia of carp virus (SVCV) and poly(I:C) and enhanced virus replication by targeting key elements of the RLR signaling pathway (MAVS, MITA, TBK1, IRF3 and IRF7). Mechanistically, DDX5 directly interacted with TBK1 to promote its autophagy-mediated degradation. Moreover, DDX5 was shown to block the interaction between TRAF3 and TBK1, hence preventing nuclear translocation of IRF3. Together, these data shed light on the roles of DDX5 in regulating IFN response.

Expression of PnSS Promotes Squalene and Oleanolic Acid (OA) Accumulation in Aralia elata via Methyl Jasmonate (MeJA) Induction.

Aralia elata is an important herb due to the abundance of pentacyclic triterpenoid saponins whose important precursors are squalene and OA. Here, we found that MeJA treatment promoted both precursors accumulation, especially the latter, in transgenic A. elata, overexpressing a squalene synthase gene from Panax notoginseng(PnSS). In this study, Rhizobium-mediated transformation was used to express the PnSS gene. Gene expression analysis and high-performance liquid chromatography (HPLC) were used to identify the effect of MeJA on squalene and OA accumulation. The PnSS gene was isolated and expressed in A. elata. Transgenic lines showed a very high expression of the PnSS gene and farnesyl diphosphate synthase gene (AeFPS) and a slightly higher squalene content than the wild-type, but endogenous squalene synthase (AeSS), squalene epoxidase (AeSE), and ß-amyrin synthase (Aeß-AS) gene were decreased as well as OA content. Following one day of MeJA treatment, the expression levels of PeSS, AeSS, and AeSE genes increased significantly. On day 3, the maximum content of both products reached 17.34 and 0.70 mg·g-1, which increased 1.39- and 4.90-fold than in the same lines without treatment. Transgenic lines expressing PnSS gene had a limited capability to promote squalene and OA accumulation. MeJA strongly activated their biosynthesis pathways, leading to enhance yield.

A single-center, retrospective analysis of 17 cases of hemolytic disease of the fetus and newborn caused by anti-M antibodies.

OBJECTIVE: We aimed to summarize the laboratory findings and clinical features of hemolytic disease of the fetus and newborn (HDFN). METHODS: We retrospectively analyzed the data for 17 infants with anti-M-induced HDFN (anti-M-HDFN) diagnosed between June 2013 and May 2019. Their maternal history, neonatal diagnosis on admission, and laboratory test results were compared with those of 15 infants with HDFN involving the ABO blood group system, 15 infants with HDFN involving the Rh system, and 15 premature infants. RESULTS: In the anti-M-HDFN group, 94.12% (16/17), 35.29% (6/17), and 17.65% (3/17) had free antibodies in plasma, a positive direct antiglobulin test, and a positive elution test, respectively. In 12 infants, free antibody reactions were stronger at 4°C than at 37°C, and the antibody titer at 4°C ranged from 1 to 512. All 17 infants with anti-M-HDFN developed anemia: 14 were treated with blood transfusion and 1 with neonatal exchange transfusion. Sixteen infants improved, and one died. Anti-M-HDFN had a higher rate of maternal stillbirth, lower gestational age, lower birthweight, and higher incidence of respiratory distress than other HDFN types. CONCLUSION: Anti-M may cause HDFN. It may present with varying degrees of anemia, low regenerative anemia, and low bilirubin levels. In addition, infants with anti-M-HDFN may have a negative elution test and direct antiglobulin test. These tests are helpful in examining antibody responses at a low temperature of 4°C.

T-cell lymphoma in a Himalayan black bear in China.

A 12-y-old Himalayan black bear suddenly developed depression, anorexia, cough, and dyspnea and died at the Ordos Zoo, China. At autopsy, the mesenteric and cranial mediastinal lymph nodes (LNs) were enlarged; the largest cranial mediastinal LN was ~13 cm in diameter. Scattered-to-diffuse, rounded-or-oval, gray, firm 1-6-mm nodules were observed on the surfaces of the spleen, liver, lungs, and small intestine. Histologically, the enlarged cranial mediastinal and mesenteric LNs, spleen, small intestine, lungs, and liver contained dense populations of neoplastic lymphoid cells (NLCs). The NLCs were round-or-oval with small amounts of mildly eosinophilic cytoplasm and round-or-oval hyperchromatic nuclei with indistinct nucleoli; the mitotic count was 55 in 2.37 mm2. Immunohistochemically, cell membranes and the cytoplasm of NLCs were CD3+, CD79a-, CD20-, CD15-, CD30-, and CD45RA-; hence, the NLCs were derived from T lymphocytes. To our knowledge, T-cell lymphoma has not been reported previously in a Himalayan black bear.

A Review of Temperature Effects on Membrane Filtration.

Membrane technology plays a vital role in drinking water and wastewater treatments. Among a number of factors affecting membrane performance, temperature is one of the dominant factors determining membrane performance. In this review, the impact of temperature on membrane structure, fouling, chemical cleaning, and membrane performance is reviewed and discussed with a particular focus on cold temperature effects. The findings from the literature suggest that cold temperatures have detrimental impacts on membrane structure, fouling, and chemical cleaning, and thus could negatively affect membrane filtration operations and performance, while warm and hot temperatures might expand membrane pores, increase membrane flux, improve membrane chemical cleaning efficiency, and interfere with biological processes in membrane bioreactors. The research gaps, challenges, and directions of temperature effects are identified and discussed indepth. Future studies focusing on the impact of temperature on membrane processes used in water and wastewater treatment and the development of methods that could reduce the adverse effect of temperature on membrane operations are needed.

Correction: State-of-the-art advancements of atomically thin two-dimensional photocatalysts for energy conversion.

Correction for 'State-of-the-art advancements of atomically thin two-dimensional photocatalysts for energy conversion' by Wa Gao et al., Chem. Commun., 2022, 58, 9594-9613, https://doi.org/10.1039/D2CC02708A.

Efficiently suppress of ferroptosis using deferoxamine nanoparticles as a new method for retinal ganglion cell protection after traumatic optic neuropathy.

Traumatic optic neuropathy (TON) is the major contributor to optic nerve damage, where the retinal ganglion cells (RGCs) are substantially lost. However, the underlying pathological mechanisms for these conditions remain largely elusive. Present work conducted a study on TON rat model, where the iron-dependent cyclooxygenase-2 (COX-2) overexpression and lipid peroxidation were observed in RGCs, suggesting ferroptosis, an iron-dependent non-apoptotic cell death, is involved in TON-induced death of RGCs. Hence, the newly formulated hyaluronic acid (HA)-based deferoxamine (DFO) nanoparticles (DFO-NPs) were intravitreally administrated in the rat model. It was hypothesized that the effective delivery of DFO, iron chelator, to the RGCs might rescue RGC ferroptosis from TON-induced injury. Also, since DFO is poor in bioavailability and of very short half-life in vivo, its safe and efficient intravitreal delivery is critical. Therefore, DFO-NPs were prepared by chemical grafting DFO onto HA molecules, and then crosslinking them in microemulsion bubbles for nanoparticles formulation. The nanoparticles were highly accumulated around the ganglionic cells and DFO uptake was increased in RGCs, accompanied by the significantly inhibited the overexpression of COX-2 and inactivation of glutathione peroxidase 4 (GPX4). These results indicate that DFO-NPs acted as an effective ferroptosis inhibitor, for the prevention of TON-induced RGC death. The current study provides new insights into the underlying mechanism of TON-induced RGC death, which may help to explore a novel strategy for the treatment of TON.

State-of-the-art advancements of atomically thin two-dimensional photocatalysts for energy conversion.

Excessive use of fossil fuels leads to energy shortages and environmental pollution, threatening human health and social development. As a clean, green, and sustainable technology, generation of renewable energy from solar light through photocatalysis has received increasing attention to cope with the impending energy and environmental crisis. The atomically thin two-dimensional (2D) semiconductors with large surface area and abundant low-coordinate surface atoms prove to exhibit enormous potential to attain efficient photocatalytic performance. These 2D ultrathin materials can shorten the transport distance of charge carriers from the interior to the surface, enhance reactants' (e.g. CO2 and H2O) adsorption and activation to lower the energy barrier, promote specific reaction processes and inhibit competitive reactions, and regulate the efficiency and selectivity of the catalytic reaction. This Feature article provides a concise overview of the preparation, catalytic mechanism, strategies for boosting the photoconversion performance, various photocatalytic applications, and characterization techniques of atomically thin 2D semiconductors. The major challenges and opportunities of the ultrathin photocatalysts are also addressed. It is hoped that this review can provide useful guidelines toward further research on 2D nanocatalysts, and inspire practical applications of these unique materials for energy conversion.

Advances in lytic polysaccharide monooxygenases with the cellulose-degrading auxiliary activity family 9 to facilitate cellulose degradation for biorefinery.

One crucial step in processing the recalcitrant lignocellulosic biomass is the fast hydrolysis of natural cellulose to fermentable sugars that can be subsequently converted to biofuels and bio-based chemicals. Recent studies have shown that lytic polysaccharide monooxygenase (LPMOs) with auxiliary activity family 9 (AA9) are capable of efficiently depolymerizing the crystalline cellulose via regioselective oxidation reaction. Intriguingly, the catalysis by AA9 LPMOs requires reductant to provide electrons, and lignin and its phenolic derivatives can be oxidized, releasing reductant to activate the reaction. The activity of AA9 LPMOs can be enhanced by in-situ generation of H2O2 in the presence of O2. Although scientific understanding of these enzymes remains somewhat unknown or controversial, structure modifications on AA9 LPMOs through protein engineering have emerged in recent years, which are prerequisite for their extensive applications in the development of cellulase-mediated lignocellulosic biorefinery processes. In this review, we critically comment on advances in studies for AA9 LPMOs, i.e., characteristic of AA9 LPMOs catalysis, external electron donors to AA9 LPMOs, especially the role of the oxidization of lignin and its derivatives, and AA9 LPMOs protein engineering as well as their extensive applications in the bioprocessing of lignocellulosic biomass. Perspectives are also highlighted for addressing the challenges.