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Concentrating solar power (CSP) tower plants using molten salt as the heat transfer fluid are currently the predominant technology used globally, and have experienced rapid development in recent years. The molten salt receiver, as the core piece of equipment for converting solar energy into thermal energy, directly determines the system efficiency, while its safety affects the plant’s operating hours. This paper reviews the details and operational status of commercial-scale CSP tower plants worldwide as of the end of 2023. It systematically summarizes the typical thermal models for mainstream tubular molten salt receivers by reviewing 37 models, including 11 three-dimensional (3D) numerical models, 8 two-dimensional (2D) semi-empirical models, and 18 one-dimensional (1D) semi-empirical models. By comparing and analyzing the key features of each model, the study concludes that detailed 3D numerical models are effective for monitoring overheating during operation, 2D semi-empirical models enable the rapid evaluation of receiver configurations, and 1D semi-empirical models support transient mass flow calculations and annual power generation estimations. Additionally, the paper outlines the current applications of receiver thermal models in system integration, particularly in combining CSP tower systems with other energy systems.

A one-stop centralized database, ZymOmics, was constructed for Zymomonas mobilis.A pipeline was developed for searching restriction–modifications, CRISPR/Cas, and toxin–antitoxin systems within a given microorganism.A genome-wide iterative and continuous editing (GW-ICE) system was established for efficient genome editing without protospacer-adjacent motif (PAM) limitations.A genome-reduced strain, ZMNPΔhypo, was constructed for further genome minimization. Current biotechnology relies on a few well-studied model organisms, such as Escherichia coli and Saccharomyces cerevisiae, for which abundant information and efficient toolkits are available for genetic manipulation, but which lack industrially favorable characteristics. Non-model industrial microorganisms usually do not have effective and/or efficient genome-engineering toolkits, which hampers the development of microbial cell factories to meet the fast-growing bioeconomy. In this study, using the non-model ethanologenic bacterium Zymomonas mobilis as an example, we developed a workflow to mine and temper the elements of restriction–modification (R-M), CRISPR/Cas, toxin–antitoxin (T-A) systems, and native plasmids, which are hidden within industrial microorganisms themselves, as efficient genome-editing toolkits, and established a genome-wide iterative and continuous editing (GW-ICE) system for continuous genome editing with high efficiency. This research not only provides tools and pipelines for engineering the non-model polyploid industrial microorganism Z. mobilis efficiently, but also sets a paradigm to overcome biotechnological limitations in other genetically recalcitrant non-model industrial microorganisms. Graphical abstract [Display omitted] The genome-wide iterative and continuous editing (GW-ICE) system developed in this study for Zymomonas mobilis can be further improved by increasing the efficiencies of homologous recombination and genome editing for multiple and large-fragment deletions and insertions, which can also be quickly applied to other microorganisms by obtaining information about endogenous restriction-modification (R-M), CRISPR/Cas, toxin-antitoxin (T-A) systems, and replication systems by uploading nucleic acid or amino acid sequences to the website http://ZymOmics.cn/CRISPR_TA_RM. The existence of at least one component of GW-ICE among 51.9% of the 2492 microbial genera, especially industrial microorganisms, such as Escherichia, Bacillus, and Clostridium, suggests that most microorganisms contain the endogenous elements and devices required for the development of GW-ICE. The application of heterologous components to build the GW-ICE system also suggested that this system can be developed for industrial microorganisms lacking potential endogenous components, although the compatibility and adaptability of these components are the basis for realizing this possibility, and high-throughput mutation and screening are required to obtain the desired components. In addition, extensive efforts are still needed to characterize the components and function of GW-ICE system, such as endogenous R-M, CRISPR/Cas, T-A, and replication systems, and novel defense systems, which have not yet been characterized. Moreover, factors affecting the efficiency of GW-ICE, including the efficiencies of homologous recombination and genome editing, and differences in protospacer-adjacent motif (PAM) sequences and donor lengths, should be better characterized. A protein prediction model integrating artificial intelligence (AI) technology and big data analysis could also expand the components for the development of efficient GW-ICE. A ‘Swiss Army knife’-like toolkit, genome-wide iterative and continuous editing (GW-ICE) system, for continuous genome editing in Zymomonas mobilis, can be generalized to other recalcitrant microorganisms by mining the genetic components of restriction–modification (R-M), CRISPR/Cas, and toxin–antitoxin (T-A) systems as well as expression systems through the website http://ZymOmics.cn/CRISPR_TA_RM.

Solid particles are generally considered to be the most suitable heat transfer fluid (HTF) and thermal energy storage (TES) materials for the next‐generation concentrated solar power (CSP) plant. The operating temperature of the solar receiver can be raised to exceed 800°C by the application of appropriate solid particles. In this way, power conversion efficiencies greater than 50% can be achieved with the supercritical carbon dioxide (sCO2) Brayton cycle. Solid particle solar receiver (SPSR) is the key equipment to absorb the concentrated solar flux, and its thermal performance is remarkably affected by receiver system designs, particle flow characteristics, and properties of solid particulate materials. This paper provides an in‐depth review of various SPSR technologies, as well as pertinent solid particle selections, optimization of the receiver system structures, particle flow characteristics, and heat transfer characteristics. The technical drawbacks, the large‐scale development prospects, and the potential optimization strategies of the various SPSR designs are highlighted by the comparative analysis of multiple parameters. This review summarizes the various solid particle solar receiver technologies that are of great interest to both academia and industry. The relevant solid particle selections, optimization of the receiver system structures, particle flow characteristics, and heat transfer characteristics are discussed. Finally, we conclude the technical drawbacks, the large‐scale development prospects, and the potential optimization strategies of the multiple designs.

BackgroundButanol derived from renewable resources by microbial fermentation is considered as one of not only valuable platform chemicals but alternative advanced biofuels. However, due to low butanol concentration in fermentation broth, butanol production is restricted by high energy consumption for product recovery. For in situ butanol recovery techniques, such as gas stripping and pervaporation, the common problem is their low efficiency in harvesting and concentrating butanol. Therefore, there is a necessity to develop an advanced butanol recovery technique for cost-effective biobutanol production.ResultsA close-circulating vapor stripping-vapor permeation (VSVP) process was developed with temperature-difference control for single-stage butanol recovery. In the best scenario, the highest butanol separation factor of 142.7 reported to date could be achieved with commonly used polydimethylsiloxane membrane, when temperatures of feed solution and membrane surroundings were 70 and 0 °C, respectively. Additionally, more ABE (31.2 vs. 17.7 g/L) were produced in the integrated VSVP process, with a higher butanol yield (0.21 vs. 0.17 g/g) due to the mitigation of butanol inhibition. The integrated VSVP process generated a highly concentrated permeate containing 212.7 g/L butanol (339.3 g/L ABE), with the reduced energy consumption of 19.6 kJ/g-butanol.ConclusionsTherefore, the present study demonstrated a well-designed energy-efficient technique named by vapor stripping-vapor permeation for single-stage butanol removal. The butanol separation factor was multiplied by the temperature-difference control strategy which could double butanol recovery performance. This advanced VSVP process can completely eliminate membrane fouling risk for fermentative butanol separation, which is superior to other techniques.

Planar light concentrators are potential applications for solar thermal conversion, in which the intensity of the electric field will exhibit strongly non-uniform characteristics. However, previous research has long ignored the solar absorption performance of plasmonic nanoparticles in the focused electric field. In this work, we use the finite element method (FEM) to study the optical behaviors of a single nanoparticle and multiple nanoparticles in the focused electric field formed by vertically and inwardly imposing the initial incident light on a quarter cylindrical surface. The results show that the focused electric field can significantly improve the solar absorption abilities compared with the parallel one for all the nanoparticles due to the local near-electric field enhancement caused by the aggregation of the free electrons on the smaller zone. Further studies on the focused electric field reveal that the plasmon heating behavior of Au spheres presents a rising trend with the decrease in inter-particle spacing, as the gap is less than the radius of Au spheres. As the number of nanoparticles increases along the focal line, the absorption power of the center nanoparticles gradually tends to be stable, and it is much lower than that of a single nanoparticle. As the nanoparticles are arranged along the y and z directions, the heterogeneity of the electric field makes the optical properties uneven. Notably, the strongest electric field appears slightly close to the incident surface rather than on the focal line.

Acetic acid is present in cellulosic hydrolysate as a potent inhibitor, and the superior acetic acid tolerance of Saccharomyces cerevisiae ensures good cell viability and efficient ethanol production when cellulosic raw materials are used as substrates. In this study, a mutant strain of S. cerevisiae ATCC4126 (Sc4126-M01) with improved acetic acid tolerance was obtained through screening strains transformed with an artificial zinc finger protein transcription factor (ZFP-TF) library. Further analysis indicated that improved acetic acid tolerance was associated with improved catalase (CAT) activity. The ZFP coding sequence associated with the improved phenotype was identified, and real-time RT-PCR analysis revealed that three of the possible genes involved in the enhanced acetic acid tolerance regulated by this ZFP-TF, namely YFL040W, QDR3, and IKS1, showed decreased transcription levels in Sc4126-M01 in the presence of acetic acid, compared to those in the control strain. Sc4126-M01 mutants having QDR3 and IKS1 deletion (ΔQDR3 and ΔIKS1) exhibited higher acetic acid tolerance than the wild-type strain under acetic acid treatment. Glucose consumption rate and ethanol productivity in the presence of 5 g/L acetic acid were improved in the ΔQDR3 mutant compared to the wild-type strain. Our studies demonstrated that the synthetic ZFP-TF library can be used to improve acetic acid tolerance of S. cerevisiae and that the employment of an artificial transcription factor can facilitate the exploration of novel functional genes involved in stress tolerance of S. cerevisiae.

BackgroundCorn stover (CS) is evaluated as the most favorable candidate feedstock for butanol production via microbial acetone–butanol–ethanol (ABE) fermentation by Clostridium acetobutylicum. By independent acid pretreatment and enzymatic hydrolysis, fermentable sugars (mainly glucose and xylose) were released, of which glucose was naturally utilized as the most preferred carbon source by C. acetobutylicum. However, the ABE fermentation using corn stover hydrolysate (CSH) without detoxification is typically limited to poor sugars utilization, butanol production and productivity. In the presence of pretreatment-derived inhibitors, the intracellular ATP and NADH, as important factors involved in cell growth, solventogenesis initiation and stress response, are exceedingly challenged owing to disrupted glucose phosphotransferase system (PTS). Therefore, there is a necessity to develop effective engineering approaches to overcome these limitations for high-efficient butanol production from CSH without detoxification.ResultsPTS-engineered C. acetobutylicum strains were constructed via overexpression and knockout of gene glcG encoding glucose-specific PTS IICBA, which pleiotropically regulated glucose utilization, cell growth, solventogenesis and inhibitors tolerance. The PTSGlcG-overexpressing strain exhibited high fermentation efficiency, wherein butanol production and productivity was 11.1 g/L and 0.31 g/L/h, compared to those of 11.0 g/L and 0.15 g/L/h with the PTSGlcG-deficient strain. During CSH culture without detoxification, the PTSGlcG-overexpressing strain exhibited desirable inhibitors tolerance and solventogenesis with butanol production of 10.0 g/L, increased by 300% and 400% compared to those of 2.5 and 2.0 g/L with the control and PTSGlcG-deficient strains, respectively. As a result of extra glucose and 10 g/L CaCO3 addition into CSH, butanol production and productivity were further maximized to 12.5 g/L and 0.39 g/L/h. These validated improvements on the PTSGlcG-overexpressing strain were ascribed to not only efficient glucose transport but also its cascading effects on intracellular ATP and NADH generation, solventogenesis initiation and inhibitors tolerance at the exponential growth phase.ConclusionThe PTSGluG regulation could be an effective engineering approach for high-efficient ABE fermentation from lignocellulosic hydrolysates without detoxification or wastewater generation, providing fundamental information for economically sustainable butanol production with high productivity.

A microbial floc consisting of a community of microbes embedded in extracellular polymeric substances matrix can provide microbial resistances to toxic chemicals and harsh environments. Phenol is a toxic environmental pollutant and a typical lignin-derived phenolic inhibitor. In this study, we genetically engineered Escherichia coli cells by expressions of diguanylate cyclases (DGCs) to promote proteinaceous and aliphatic biofloc formation. Compared with the planktonic E. coli cells, the biofloc-forming cells improved phenol removal rate by up to 2.2-folds, due to their substantially improved tolerance (up to 149%) to phenol and slightly enhanced cellular activity (20%) of phenol hydroxylase (PheH). The engineered bioflocs also improved E. coli tolerance to other toxic compounds such as furfural, 5-hydroxymethylfurfural, and guaiacol. Additionally, the strategy of the engineered biofloc formation was applicable to Pseudomonas putida and enhanced its tolerance to phenol. This study highlights a strategy to form engineered bioflocs for improved cell tolerance and removal of toxic compounds, enabling their universality of use in bioproduction and bioremediation.

Xylanase is the enzyme complex that is responsible for the degradation of xylan; however, novel xylanase producers remain to be explored in marine environment. In this study, a Streptomyces strain M11 which exhibited xylanase activity was isolated from marine sediment. The 16S rDNA sequence of M11 showed the highest identity (99 %) to that of Streptomyces viridochromogenes . The xylanase produced from M11 exhibited optimum activity at pH 6.0, and the optimum temperature was 70 °C. M11 xylanase activity was stable in the pH range of 6.0–9.0 and at 60 °C for 60 min. Xylanase activity was observed to be stable in the presence of up to 5 M NaCl. Antibiotic-resistant mutants of M11 were isolated, and among the various antibiotics tested, streptomycin showed the best effect on obtaining xylanase overproducer. Mutant M11-1(10) isolated from 10 μg/ml streptomycin-containing plate showed 14 % higher xylanase activities than that of the wild-type strain. An analysis of gene rpsL (encoding ribosomal protein S12) showed that rpsL from M11-1(10) contains a K88R mutation. This is the first report to show that marine-derived S. viridochromogenes strain can be used as a xylanase producer, and utilization of ribosome engineering for the improvement of xylanase production in Streptomyces was also first successfully demonstrated.

Background Butanol as an important chemical and potential fuel could be produced via ABE fermentation from lignocellulosic biomass. The use of food-related feedstocks such as maize and sugar cane may not be a sustainable solution to world’s energy needs. Recently, Jerusalem artichoke tubers containing inulin have been used as feedstock for butanol production, but this bioprocess is not commercially feasible due to the great value of inulin as functional food. Till now, there is a gap on the utilization of Jerusalem artichoke stalk (JAS) as feedstock for microbial butanol production. Results Biobutanol production from JAS was investigated in order to improve cellulose digestibility and efficient biobutanol fermentation. Compared with 9.0 g/L butanol (14.7 g/L ABE) production by 2% NaOH pretreatment of JAS, 11.8 g/L butanol (17.6 g/L ABE) was produced in the best scenario conditions of NaOH-H2O2 pretreatment, washing times and citrate buffer strengths etc. Furthermore, more than >64% water in washing pretreated JAS process could be saved, with improving butanol production by >25.0%. To mimic in situ product recovery for ABE fermentation, the vapor stripping-vapor permeation (VSVP) process steadily produced 323.4-348.7 g/L butanol (542.7-594.0 g/L ABE) in condensate, which showed more potentials than pervaporation for butanol recovery. Conclusions Therefore, the present study demonstrated an effective strategy on efficient biobutanol production using lignocellulosic biomass. The process optimization could contribute to significant reduction of wastewater emission and the improvement of lignocellulosic biomass digestibility and biobutanol production, which makes biobutanol production more efficient using JAS.