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Lignocellulosic biomass, including agricultural, forestry, and energy crop waste, is one of Earth’s most abundant renewable resources, accounting for approximately 50% of global renewable resources. It contains cellulose, hemicellulose, and lignin, making it crucial for biofuels and bio-based chemicals. Due to its complex structure, single-pretreatment methods are inefficient, leading to the development of combined pretreatment technologies. These methods enhance cellulose accessibility and conversion efficiency. This paper analyzes the principles, advantages, and disadvantages of various combined pretreatment methods and their practical benefits. It highlights recent research achievements and applications in biofuel, biochemical production, and feed. By integrating multiple pretreatment methods, biomass degradation efficiency can be significantly improved, energy consumption reduced, and chemical reagent use minimized. Future advancements in combined physical, chemical, and biological pretreatment technologies will further enhance biomass utilization efficiency, reduce energy consumption, and protect the environment, providing robust support for sustainable renewable energy development and ecological protection.

Abstract As one of the mainstream biodegradable materials, poly(butylene adipate-co-terephthalate) (PBAT) foams offer a sustainable alternative to traditional plastic foams, effectively reducing environmental pollution. However, the high cost and poor mechanical performance of PBAT foams impede their practical application. Herein, the glycidyl methacrylate-grafted biomass lignin (GML) was used to produce a PBAT/GML composite foam with good foaming performance and mechanical properties at high lignin-filling amounts by twin-screw melting free radical polymerization and supercritical CO2 foaming process. The compatibility of GML in the PBAT matrix was improved due to the formation of ester bonds in modified lignin, endowing the PBAT/GML (PGML) composite foam with exceptional foaming performance. Additionally, the mechanical properties of PGML composite foam were remarkably enhanced due to the introduction of the abundant aromatic structures of GML and the construction of a stable covalent crosslinking network. The compressive strengths and compression modulus of the PGML foam were improved by 2.53 times and 2.47 times, while its bending strength and bending modulus were improved by 1.27 times and 3.92 times compared to the neat PBAT. This research affords a new strategy for developing low-cost biodegradable biomass PBAT/lignin composite foam materials with good foaming performance and mechanical properties. Graphical abstract

1,4-butanediol (1,4-BDO) is an important building block in the chemical industry that has been mainly produced from fossil fuels, but now biosynthesis of 1,4-BDO has received more and more attention due to environmental issues. The Clostridia C4 pathway produces an intermediate crotonyl-CoA which could be diverted to 1,4-BDO by 4-hydroxybutyryl-CoA dehydratase (4HBD). Here, we compared this pathway with other 1,4-BDO biosynthesis pathways and illustrated its potential advantages regarding cellular energy conservation and theoretical yield. Then, the feasibility of 1,4-BDO production in this way was tested by introducing a single 4HBD in Clostridium acetobutylicum that natively produced the C4 intermediate and a variety of aldehyde/alcohol dehydrogenases (AdhE). Five different 4HBD genes were screened and the Cbei-2100 gene from Clostridium beijerinckii was the most effective, producing 0.066 mg/mL of 1,4-BDO. To block the metabolic flux towards the main product butanol, disruption of butyryl-CoA dehydrogenase (Bcd) was tried but failed, while inactivation of its homologue (FAD/FMN-containing dehydrogenase, Fcd) obtained little effect. Alternatively, the electron-transferring flavoprotein EtfA coupled with Bcd was inactivated, and 1,4-BDO production was greatly increased to 0.182 mg/mL. In conclusion, this study demonstrated the feasibility of 1,4-BDO production through the Clostridia C4 pathway. Further blocking of the competing flux towards butanol would be effective to improve the production of in the future.

The peroxygenases are ideal biocatalysts for the selective oxyfunctionalisation of stable C–H bonds. However, the catalytic efficiency of this approach is limited due to enzyme lability toward oxidant H2O2. Although the reported in-situ H2O2 generation system enables the stable biocatalytic process without deactivating the enzyme, the greatest catalytic potential of peroxygenases still cannot be fulfilled effectively. To address the above issue, a H2O2 generation-detection-regulation platform that integrated an effective organocatalyst-driven H2O2 generation system, a precise electrochemical H2O2 real-time detection device, and a convenient H2O2 regulation strategy was first developed. The suitable range of H2O2 generation rate for maximizing the catalytic efficiency of peroxygenases while minimizing inactivation of the enzyme was firstly obtained by simply adjusting the amount of organocatalyst. According to the determined suitable range, the C–H oxyfunctionalisation efficiency of peroxygenases for each substrate was significantly boosted, achieving ∼3-fold of the reported highest turnover frequency.

Biofilms can enhance industrial fermentation efficiency by increasing cell density, stability, and metabolic activity and have been successfully applied to the continuous production of many small-molecule chemicals. However, the continuous production of proteins by biofilms has been less studied. This study used secretory human epidermal growth factor (hEGF) as a representative product to evaluate and optimize biofilm-based continuous protein production. First, by deleting the protease and overexpressing eight key genes involved in protein secretion in Saccharomyces cerevisiae, the yield of hEGF was improved by 82.6% from 77.4 to 141.3 mg/L in shake flasks. Subsequently, the flocculation genes FLO11 and ALS3 were introduced to facilitate the establishment of a biofilm-based continuous immobilization fermentation model. The optimal strain SIC-ALS3-PDI1 produced 583.8 mg/L of hEGF, with a productivity of 4.9 mg/L/h during traditional free-cell fermentation, while it produced an average of 300.0 mg/L of hEGF in 10 continuous batches of biofilm-based fermentation, with a productivity of 6.3 mg/L/h. Although the hEGF production in biofilms was lower than that in free-cell fermentation, biofilm fermentation demonstrated greater productivity, with the advantage of not requiring seed culture for each batch of fermentation. This study provided a valuable reference for the biofilm-based production of other peptides.

Considerable progress has been made in recent years to the development of sustainable polymers from bio-based feedstocks. In this study, 100% bio-based nylons were prepared via an integrated chemical and biological process from lignocellulose. These novel nylons were obtained by the melt polymerization of 3-propyladipic acid derived from lignin and 1,5-pentenediamine/1,4-butanediamine derived from carbohydrate sugar. Central to the concept is a three-step noble metal free catalytic chemical funnelling sequence (Raney Ni mediated reductive catalytic fractionation - reductive funnelling - oxidative funnelling), which allowed for obtaining a single component 3-propyladipic acid from lignin with high efficiency. The structural and thermodynamic properties of the obtained nylons have been systematically investigated, and thus obtained transparent bio-based nylons exhibited higher Mw (>32,000) and excellent thermal stability (Td5% > 265 °C). Considering their moderate Tg and good melt strength, these transparent bio-based nylons could serve as promising functional additives or temperature-responsive materials.

Abstract Background Biofilm-immobilized continuous fermentation has the potential to enhance cellular environmental tolerance, maintain cell activity and improve production efficiency. Results In this study, different biofilm-forming genes (FLO5, FLO8 and FLO10) were integrated into the genome of S. cerevisiae for overexpression, while FLO5 and FLO10 gave the best results. The biofilm formation of the engineered strains 1308-FLO5 and 1308-FLO10 was improved by 31.3% and 58.7% compared to that of the WT strain, respectively. The counts of cells adhering onto the biofilm carrier were increased. Compared to free-cell fermentation, the average ethanol production of 1308, 1308-FLO5 and 1308-FLO10 was increased by 17.4%, 20.8% and 19.1% in the biofilm-immobilized continuous fermentation, respectively. Due to good adhering ability, the fermentation broth turbidity of 1308-FLO5 and 1308-FLO10 was decreased by 22.3% and 59.1% in the biofilm-immobilized fermentation, respectively. Subsequently, for biofilm-immobilized fermentation coupled with membrane separation, the engineered strain significantly reduced the pollution of cells onto the membrane and the membrane separation flux was increased by 36.3%. Conclusions In conclusion, enhanced biofilm-forming capability of S. cerevisiae could offer multiple benefits in ethanol fermentation. Graphical Abstract

Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is a bifunctional enzyme located in the mitochondria. MTHFD2 has been reported to be overexpressed in several malignant tumors and is implicated in cancer development. This study aimed to investigate the effect of MTHFD2 on ovarian cancer progression. The expression of MTHFD2 was detected by bioinformatic analysis, immunohistochemistry, RT‐qPCR (real‐time quantitative PCR analysis), and western blot analysis. The effects of MTHFD2 depletion on cell proliferation, migration, and invasion were determined through in vitro experiments. Cell cycle progression and apoptosis were accessed by flow cytometry. The related signaling pathway protein expression was determined by western blot analysis. We found that MTHFD2 is highly expressed in both ovarian cancer tissues and cell lines. MTHFD2 deletion suppressed cell proliferation and metastasis. Knockdown of MTHFD2 induces cell apoptosis and G2/M arrest, whereas the number of cells in S phase increased with MTHFD2 overexpression. Mechanically, our results indicate that an inhibitory effect of MTHFD2 knockdown may be mediated by the downregulation of cyclin B1/Cdc2 complex and the inhibitory effect on its activity. Additionally, MTHFD2 could regulate cell growth and aggressiveness via activation of STAT3 and the STAT3‐induced epithelial–mesenchymal transition signaling pathway. These findings indicate that MTHFD2 is overexpressed in ovarian cancer and regulates cell proliferation and metastasis, presenting an attractive therapeutic target.

Abstract Background Lactones are important compounds in the field of medicine, material and chemical industry. One of the promising accesses to these flexible scaffolds is NAD(P)+-dependent alcohol dehydrogenases-catalyzed oxidative lactonization of diols, which relies on the construction of an efficient NAD(P)+ regeneration system. Results In this study, a novel system combining horse liver alcohol dehydrogenase (HLADH) with the synthetic bridged flavin cofactor was established for biosynthesis of lactones. The reaction conditions of this system were optimized and a variety of lactones including chiral lactones were efficiently obtained from various diols. Compared to the previously reported NAD(P)+-regeneration systems, this system showed better regeneration efficiency and product yield. A two-phase system was further applied to solve the problem of product inhibition, and 80% yield was obtained at the condition of 300 mM substrate. Conclusions This study provides an efficient method to synthesis of lactones from diols under mild conditions. We believe this system will be a promising alternative to promote the synthesis of other valuable compounds. Graphic abstract

Air quality in dental clinics is critical, especially in light of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, given that dental professionals and patients are at risk of regular exposure to aerosols and bioaerosols in dental clinics. High levels of ultrafine particles (UFP) may be produced by dental procedures. This study aimed to quantify ultrafine particles (UFP) concentrations in a real multi-chair dental clinic and compare the levels of UFP produced by different dental procedures. The efficiency of a high-volume evacuator (HVE) in reducing the UFP concentrations during dental procedures was also assessed. UFP concentrations were measured both inside and outside of a dental clinic in Shanghai, China during a 12-day period from July to September 2020. Dental activities were recorded during working hours. The mean (±standard deviation) concentrations of indoor and outdoor UFP during the sampling period were 8,209 (±4,407) counts/cm3 and 15,984 (±7,977) counts/cm3, respectively. The indoor UFP concentration was much higher during working hours (10,057 ± 5,725 counts/cm3) than during non-working hours (7,163 ± 2,972 counts/cm3). The UFP concentrations increased significantly during laser periodontal treatment, root canal filling, tooth drilling, and grinding, and were slightly elevated during ultrasonic scaling or tooth extraction by piezo-surgery. The highest UFP concentration (241,136 counts/cm3) was observed during laser periodontal treatment, followed by root canal filling (75,034 counts/cm3), which showed the second highest level. The use of an HVE resulted in lower number concentration of UFP when drilling and grinding teeth with high-speed handpieces, but did not significantly reduce UFP measured during laser periodontal therapy. we found that many dental procedures can generate high concentration of UFP in dental clinics, which may have a great health impact on the dental workers. The use of an HVE may help reduce the exposure to UFP during the use of high-speed handpieces.

Biofilm cells are well-known for their increased survival and metabolic capabilities and have been increasingly implemented in industrial and biotechnological processes. Corynebacterium glutamicum is one of the most widely used microorganisms in the fermentation industry. However, C. glutamicum biofilm has been rarely reported and little is known about its cellular basis. Here, the physiological changes and characteristics of C. glutamicum biofilm cells during long-term fermentation were studied for the first time. Results showed that the biofilm cells maintained stable metabolic activity and cell size was enlarged after repeated-batch of fermentation. Cell division was slowed, and chromosome content and cell proliferation efficiency were reduced during long-term fermentation. Compared to free cells, more biofilm cells were stained by the apoptosis indicator dyes Annexin V-FITC and propidium iodide (PI). Overall, these results suggested slow-growing, long-lived cells of C. glutamicum biofilm during fermentation, which could have important industrial implications. This study presents first insights into the physiological changes and growth behavior of C. glutamicum biofilm cell population, which would be valuable for understanding and developing biofilm-based processes.

Wood–plastic composites (WPCs) are a type of environmentally friendly materials widely used in daily life. This paper selected low-value biomass, corn stalk (CS), as the lignocellulosic resource for polyvinyl chloride (PVC)-based WPCs. To depict the relationship between lignocellulosic composition (cellulose, hemicellulose, and lignin) and mechanical performance of WPCs, pretreatments have been optimized to selective removal of lignin using an alkaline-EtOH stewing process and selective removal of hemicellulose using an acid stewing process. The αC sample, in which both lignin and hemicellulose were removed, shows the highest degree of crystallinity (72.60%) as estimated from X-ray diffraction analysis results and fibrous morphology with the highest aspect ratio as seen in scanning electron microscopy images. Compared with PVC/CS, PVC/αC gives a substantial increase in tensile strength and modulus by 37.21 and 21.66% and flexural strength and modulus by 29.98 and 34.88%, respectively. These improvements lie in the reinforcing effect of a fibrous structure and the improved interfacial compatibility as proven by scanning electron microscopy and dynamic mechanical analyzer results. Considering the extracted lignin and hemicellulose can be further developed to valuable biochemicals, the pretreatment to CS adds value to both WPC materials and biorefinery products.

In this study, wheat straw was fractionated into carbohydrates (cellulose and hemicellulose) by ammonia–mechanical pretreatment for l-lactic acid fermentation. Under optimal conditions (aqueous ammonia concentration: 19% w/w, liquid–solid ratio: 2.1:1 w/w, holding time: 4.80 h), the delignification was more than 60%. After enzymatic hydrolysis, the maximum conversions of cellulose and hemicellulose were 92.5% and 83.4% based on the pretreatment residue, respectively. The wheat straw hydrolysate was used to produce l-lactic acid with Thermoanaerobacter sp. DH-217G, which obtained a yield of 88.6% and an optical purity of 99.2%. The ammonia–mechanical pretreatment is an economical method for the production of fermentable monosaccharide, providing potential for further downstream high value-added applications.

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N′-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4′-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4′-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV–Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials.

The peroxygenases are ideal biocatalysts for the selective oxyfunctionalisation of stable C-H bonds. However, the catalytic efficiency of this approach is limited due to enzyme lability toward oxidant H2O2. Although the reported in-situ H2O2 generation system enables the stable biocatalytic process without deactivating the enzyme, the greatest catalytic potential of peroxygenases still cannot be fulfilled effectively. To address the above issue, a H2O2 generation-detection-regulation platform that integrated an effective organocatalyst-driven H2O2 generation system, a precise electrochemical H2O2 real-time detection device, and a convenient H2O2 regulation strategy was first developed. The suitable range of H2O2 generation rate for maximizing the catalytic efficiency of perox-ygenases while minimizing inactivation of the enzyme was firstly obtained by simply adjusting the amount of organocatalyst. According to the determined suitable range, the C-H oxyfunctionalisation efficiency of peroxygenases for each substrate was significantly boosted, achieving ~3-fold of the reported highest turnover frequency. [ABSTRACT FROM AUTHOR]