Biodegradation: the best solution to the world problem of discarded polymers.

The widespread use of polymers has made our lives increasingly convenient by offering a more convenient and dependable material. However, the challenge of efficiently decomposing these materials has resulted in a surge of polymer waste, posing environment and health risk. Currently, landfill and incineration treatment approaches have notable shortcomings, prompting a shift towards more eco-friendly and sustainable biodegradation approaches. Biodegradation primarily relies on microorganisms, with research focusing on both solitary bacterial strain and multi-strain communities for polymer biodegradation. Furthermore, directed evolution and rational design of enzyme have significantly contributed to the polymer biodegradation process. However, previous reviews often undervaluing the role of multi-strain communities. In this review, we assess the current state of these three significant fields of research, provide practical solutions to issues with polymer biodegradation, and outline potential future directions for the subject. Ultimately, biodegradation, whether facilitated by single bacteria, multi-strain communities, or engineered enzymes, now represents the most effective method for managing waste polymers.

[Research progress in biosynthesis of arbutin].

Arbutin, a glycosylated compound of hydroquinone, exists in two forms of ß-arbutin and α-arbutin based on the configuration of the glycosidic bond. As a safe and stable whitening agent, arbutin is widely used in cosmetics, and it has antioxidant, antimicrobial, anti-inflammatory, and anti-tumor activities. The production of arbutin by plant extraction faces challenges such as long plant growth periods, complex extraction processes, and low yields. The chemical synthesis of arbutin suffers from harsh reaction conditions, poor stereo-selectivity, and low yields. In recent years, biosynthesis emerges as the most popular method to produce arbutin because of the simple and mild reaction conditions, low costs, and environmental friendliness. This review summarizes the research progress in four biosynthetic strategies for arbutin, including plant conversion, enzyme catalysis, whole-cell catalysis, and microbial fermentation. The advantages and limitations of these biosynthetic strategies are discussed, and future research directions are proposed.

[Construction of microbial cell factories for synthesizing value-added chemicals with xylose].

Lignocellulose is the most abundant renewable resource on earth. Constructing microbial cell factories for synthesizing value-added chemicals with lignocellulose is the key to realize green biomanufacturing. Xylose is the second most fermentable sugar in lignocellulose after glucose. Building microbial cell factories that can efficiently metabolize xylose is of great significance to achieve full utilization of lignocellulose. However, the lower metabolism efficiency of xylose than that of glucose in most microorganisms limits the application of xylose. In recent years, the deepening understanding of microbial metabolic mechanisms and the continuous advancement of synthetic biology have greatly improved the efficiency of microbial metabolism of xylose and expanded the spectrum of xylose-derived products. This article introduces several xylose metabolic pathways that exist in the nature and the derived products, summarizes the strategies for constructing recombinant strains that can co-utilize xylose and glucose, and reviews the research progress in the application of lignocellulose hydrolysates in the synthesis of target products. Finally, this article discusses the current technical bottlenecks and prospects the future development directions in this field.

Microbial synthesis of gallic acid and its glucoside ß-glucogallin.

Gallic acid (GA) and ß-glucogallin (BGG) are natural products with diverse uses in pharmaceutical, food, chemical and cosmetic industries. They are valued for their wide-ranging properties such as antioxidant, antibacterial, antidiabetic, and anticancer properties. Despite their significant importance, microbial production of GA and BGG faces challenges such as limited titers and yields, along with the incomplete understanding of BGG biosynthesis pathways in microorganisms. To address these challenges, we developed a recombinant Escherichia coli strain capable of efficiently producing GA. Our approach involved screening efficient pathway enzymes, integrating biosynthetic pathway genes into the genome while balancing carbon flux via adjusting expression levels, and strengthening the shikimate pathway to remove bottlenecks. The resultant strain achieved impressive results, producing 51.57 g/L of GA with a carbon yield of 0.45 g/g glucose and a productivity of 1.07 g/L/h. Furthermore, we extended this microbial platform to biosynthesize BGG by screening GA 1-O-glucosyltransferase, leading to the de novo production of 92.42 mg/L of BGG. This work establishes an efficient chassis for producing GA at an industrial level and provides a microbial platform for generating GA derivatives.

Preparation and characterization of bionics Oleosomes with high loading efficiency: The enhancement of hydrophobic space and the effect of cholesterol.

Liposomes (LIP) loaded with natural active ingredients have significant potential in the food industry. However, their low loading efficiency (LE) hampers the advancement of liposomal products. To improve the loading capacity of functional compounds, bionic oleosomes (BOLE) with a monolayer of phospholipid membranes and a glyceryl tricaprylate/caprate (GTCC) oil core have first been engineered by high-pressure homogenization. TEM revealed that the core of BOLE consists of GTCC instead of water, thereby extending the hydrophobic space. Steady-state fluorescence and active loading experiments confirmed that cholesterol (CH) detached from the phospholipid membrane and entered the oil core, where it repelled cannabidiol (CBD). Based on the extending hydrophobic space, CBD-BOLE was prepared and its LE was 3.13 times higher than CBD-LIP. The CBD-phospholipid ratio (CPR) of CBD-BOLE significantly improved at least 7.8 times. Meanwhile, the free radical scavenging activity of CBD was increased and cytotoxicity was reduced.

Preparation and Immobilization Mechanism on a Novel Composite Carrier PDA-CF/PUF to Improve Cells Immobilization and Xylitol Production.

The preparation of a novel composite carrier of polydopamine-modified carbon fiber/polyurethane foam (PDA-CF/PUF) was proposed to improve cell immobilization and the fermentation of xylitol, which is an important food sweetener and multifunctional food additive. Candida tropicalis was immobilized on the composite carrier by adsorption and covalent binding. The properties and immobilization mechanism of the composite carrier and its effect on immobilized cells were investigated. It showed that the modification of PDA enhanced the loading of CF on the PUF surface and the adhesion of cells on the composite carrier surface. Also, the biocompatibility of carriers to cells was improved. In addition, the introduction of PDA increased the active groups on the surface of the carrier, enhanced the hydrophilicity, promoted the cells immobilization, and increased the xylitol yield. It was also found that expression of the related gene XYL1 in cells was significantly increased after the immobilization of the PDA-CF/PUF composite carrier during the fermentation. The PDA-CF/PUF was an immobilized carrier with the excellent biocompatibility and immobilization performance, which has great development potential in the industrial production of xylitol.

Potential mechanisms of cancer prevention and treatment by sulforaphane, a natural small molecule compound of plant-derived.

Despite recent advances in tumor diagnosis and treatment technologies, the number of cancer cases and deaths worldwide continues to increase yearly, creating an urgent need to find new methods to prevent or treat cancer. Sulforaphane (SFN), as a member of the isothiocyanates (ITCs) family, which is the hydrolysis product of glucosinolates (GLs), has been shown to have significant preventive and therapeutic cancer effects in different human cancers. Early studies have shown that SFN scavenges oxygen radicals by increasing cellular defenses against oxidative damage, mainly through the induction of phase II detoxification enzymes by nuclear factor erythroid 2-related factor 2 (Nrf2). More and more studies have shown that the anticancer mechanism of SFN also includes induction of apoptotic pathway in tumor cells, inhibition of cell cycle progression, and suppression of tumor stem cells. Therefore, the application of SFN is expected to be a necessary new approach to treating cancer. In this paper, we review the multiple molecular mechanisms of SFN in cancer prevention and treatment in recent years, which can provide a new vision for cancer treatment.

Unlocking the potential of enzyme engineering via rational computational design strategies.

Enzymes play a pivotal role in various industries by enabling efficient, eco-friendly, and sustainable chemical processes. However, the low turnover rates and poor substrate selectivity of enzymes limit their large-scale applications. Rational computational enzyme design, facilitated by computational algorithms, offers a more targeted and less labor-intensive approach. There has been notable advancement in employing rational computational protein engineering strategies to overcome these issues, it has not been comprehensively reviewed so far. This article reviews recent developments in rational computational enzyme design, categorizing them into three types: structure-based, sequence-based, and data-driven machine learning computational design. Case studies are presented to demonstrate successful enhancements in catalytic activity, stability, and substrate selectivity. Lastly, the article provides a thorough analysis of these approaches, highlights existing challenges and potential solutions, and offers insights into future development directions.

Long-term intake of sulforaphene alleviates D-galactose-induced skin senescence by activating AMPK-Sirt 1 pathway.

D-Galactose (D-gal) accumulation triggers the generation of oxygen free radicals, resulting in skin aging. Sulforaphene (SFE), an isothiocyanate compound derived from radish seeds, possesses diverse biological activities, including protective effects against inflammation and oxidative damage. This investigation delves into the antioxidant impact of SFE on age-related skin injury. In vivo experiments demonstrate that SFE treatment significantly improves the macro- and micro-morphology of dorsal skin. It effectively diminishes the elevation of oxidative stress biomarkers in mice skin tissue treated with D-gal, concurrently enhancing the activity of antioxidant enzymes. Additionally, SFE mitigates collagen mRNA degradation, lowers pro-inflammatory cytokine levels, and downregulates MAPK-related protein expression in the skin. Moreover, SFE supplementation reduces lipid metabolite levels and elevates amino acid metabolites, such as L-cysteine and L-histidine. These findings suggest that SFE holds promise as a natural remedy to mitigate aging induced by oxidative stress.

Exploring the role of flavin-dependent monooxygenases in the biosynthesis of aromatic compounds.

Hydroxylated aromatic compounds exhibit exceptional biological activities. In the biosynthesis of these compounds, three types of hydroxylases are commonly employed: cytochrome P450 (CYP450), pterin-dependent monooxygenase (PDM), and flavin-dependent monooxygenase (FDM). Among these, FDM is a preferred choice due to its small molecular weight, stable expression in both prokaryotic and eukaryotic fermentation systems, and a relatively high concentration of necessary cofactors. However, the catalytic efficiency of many FDMs falls short of meeting the demands of large-scale production. Additionally, challenges arise from the limited availability of cofactors and compatibility issues among enzyme components. Recently, significant progress has been achieved in improving its catalytic efficiency, but have not yet detailed and informative viewed so far. Therefore, this review emphasizes the advancements in FDMs for the biosynthesis of hydroxylated aromatic compounds and presents a summary of three strategies aimed at enhancing their catalytic efficiency: (a) Developing efficient enzyme mutants through protein engineering; (b) enhancing the supply and rapid circulation of critical cofactors; (c) facilitating cofactors delivery for enhancing FDMs catalytic efficiency. Furthermore, the current challenges and further perspectives on improving catalytic efficiency of FDMs are also discussed.

Effects and mechanism of metal ions on the stability of glucosinolates in aqueous solution.

Glucosinolates (GLs) are important precursors of anticancer isothiocyanates in cruciferous plants. However, GLs in aqueous solution have been found to decompose under certain conditions, and the effect of metal ions remains unclear. In this study, high-purity glucoraphanin and glucoraphenin were used to explore the effects of metal ions with thermal treatment. The degree of GLs decomposition was affected by the type and concentration of metal ions, temperature, and duration of heating. Fe3+ (1 mM) was found to cause the decomposition of 78.1 % of glucoraphanin and 94.7 % of glucoraphenin in 12 h at 100 °C, while Cu2+ completely decomposed both GLs. The decomposition products were all the corresponding nitriles, and decomposition dynamic curves were first-order. In addition to accelerating hydrolysis, metal ions may promote the generation of nitriles as catalysts. The exploration of GLs decomposition could help to adopt more effective methods to avoid the formation of toxic compounds.

Identifying and charactering a 4-aminobutyryl-CoA ligase for the production of butyrolactam.

Butyrolactam, a crucial four-carbon molecule, serves as building block in synthesis of polyamides. While biosynthesis of butyrolactam from renewable carbon sources offers a more sustainable approach, it has faced challenges in achieving high product titer and yield. Here, an efficient microbial platform for butyrolactam production was constructed by elimination of rate-limiting step and systematic pathway optimization. Initially, a superior 4-aminobutyryl-CoA ligase was discovered and characterized among six acyl-CoA ligases from different sources, which greatly improved the pathway efficiency. Subsequent optimizations were implemented to further enhance butyrolactam production, including promoter engineering, the elimination of competing pathways, transporter engineering and improving the availability of precursors. There efforts resulted in achieving approximately 2 g/L butyrolactam in shake flask experiments. Finally, the biosynthesis of butyrolactam was scaled up in a 3-L bioreactor in 84 hours, resulting in a significantly increased production of 45.2 g/L, with a carbon yield of 0.34 g/g glucose. This study highlights the construction of a microbial platform with the capability to achieve elevated levels of butyrolactam production and unlocks its potential in sustainable manufacturing processes.

Rational protein engineering of a ketoacids decarboxylase for efficient production of 1,2,4-butanetriol from arabinose.

BACKGROUND: Lignocellulose, the most abundant non-edible feedstock on Earth, holds substantial potential for eco-friendly chemicals, fuels, and pharmaceuticals production. Glucose, xylose, and arabinose are primary components in lignocellulose, and their efficient conversion into high-value products is vital for economic viability. While glucose and xylose have been explored for such purpose, arabinose has been relatively overlooked. RESULTS: This study demonstrates a microbial platform for producing 1,2,4-butanetriol (BTO) from arabinose, a versatile compound with diverse applications in military, polymer, rubber and pharmaceutical industries. The screening of the key pathway enzyme, keto acids decarboxylase, facilitated the production of 276.7 mg/L of BTO from arabinose in Escherichia coli. Through protein engineering of the rate-limiting enzyme KivD, which involved reducing the size of the binding pocket to accommodate a smaller substrate, its activity improved threefold, resulting in an increase in the BTO titer to 475.1 mg/L. Additionally, modular optimization was employed to adjust the expression levels of pathway genes, further enhancing BTO production to 705.1 mg/L. CONCLUSION: The present study showcases a promising microbial platform for sustainable BTO production from arabinose. These works widen the spectrum of potential lignocellulosic products and lays the foundation for comprehensive utilization of lignocellulosic components.

New Insight into the Potential Protective Function of Sulforaphene against ROS-Mediated Oxidative Stress Damage In Vitro and In Vivo.

Sulforaphene (SFE) is a kind of isothiocyanate isolated from radish seeds that can prevent free-radical-induced diseases. In this study, we investigated the protective effect of SFE on oxidative-stress-induced damage and its molecular mechanism in vitro and in vivo. The results of cell experiments show that SFE can alleviate D-gal-induced cytotoxicity, promote cell cycle transformation by inhibiting the production of reactive oxygen species (ROS) and cell apoptosis, and show a protective effect on cells with H2O2-induced oxidative damage. Furthermore, the results of mice experiments show that SFE can alleviate D-galactose-induced kidney damage by inhibiting ROS, malondialdehyde (MDA), and 4-hydroxyalkenals (4-HNE) production; protect the kidney against oxidative stress-induced damage by increasing antioxidant enzyme activity and upregulating the Nrf2 signaling pathway; and inhibit the activity of pro-inflammatory factors by downregulating the expression of Toll-like receptor 4 (TLR4)-mediated inflammatory response. In conclusion, this research shows that SFE has antioxidant effects, providing a new perspective for studying the anti-aging properties of natural compounds.

High-yield production of ß-arbutin by identifying and eliminating byproducts formation.

ß-Arbutin is a plant-derived glycoside and widely used in cosmetic and pharmaceutical industries because of its safe and effective skin-lightening property as well as anti-oxidant, anti-microbial, and anti-inflammatory activities. In recent years, microbial fermentation has become a highly promising method for the production of ß-arbutin. However, this method suffers from low titer and low yield, which has become the bottleneck for its widely industrial application. In this study, we used ß-arbutin to demonstrate methods for improving yields for industrial-scale production in Escherichia coli. First, the supply of precursors phosphoenolpyruvate and uridine diphosphate glucose was improved, leading to a 4.6-fold increase in ß-arbutin production in shaking flasks. The engineered strain produced 36.12 g/L ß-arbutin with a yield of 0.11 g/g glucose in a 3-L bioreactor. Next, based on the substrate and product's structural similarity, an endogenous O-acetyltransferase was identified as responsible for 6-O-acetylarbutin formation for the first time. Eliminating the formation of byproducts, including 6-O-acetylarbutin, tyrosine, and acetate, resulted in an engineered strain producing 43.79 g/L ß-arbutin with a yield of 0.22 g/g glucose in fed-batch fermentation. Thus, the yield increased twofold by eliminating byproducts formation. To the best of our knowledge, this is the highest titer and yield of ß-arbutin ever reported, paving the way for the industrial production of ß-arbutin. This study demonstrated a systematic strategy to alleviate undesirable byproduct accumulation and improve the titer and yield of target products. KEY POINTS: • A systematic strategy to improve titer and yield was showed • Genes responsible for 6-O-acetylarbutin formation were firstly identified • 43.79 g/L ß-arbutin was produced in bioreactor, which is the highest titer so far.

Multifunctional Sodium Hyaluronate/Chitosan Foam Used as an Absorbable Hemostatic Material.

Absorbable hemostatic materials have great potential in clinical hemostasis. However, their single coagulation mechanism, long degradation cycles, and limited functionality mean that they have restricted applications. Here, we prepared a sodium hyaluronate/carboxymethyl chitosan absorbable hemostatic foam (SHCF) by combining high-molecular-weight polysaccharide sodium hyaluronate with carboxymethyl chitosan via hydrogen bonding. SHCFs have rapid liquid absorption performance and can enrich blood cells. They transform into a gel when it they come into contact with blood, and are more easily degraded in this state. Meanwhile, SHCFs have multiple coagulation effects and promote hemostasis. In a rabbit liver bleeding model, SHCFs reduced the hemostatic time by 85% and blood loss by 80%. In three severe and complex bleeding models of porcine liver injury, uterine wall injury, and bone injury, bleeding was well-controlled and anti-tissue adhesion effects were observed. In addition, degradation metabolism studies show that SHCFs are 93% degraded within one day and almost completely metabolized within three weeks. The absorbable hemostatic foam developed in this study is multifunctional; with rapid hemostasis, anti-adhesion, and rapid degradation properties, it has great clinical potential for in vivo hemostasis.

A polycistronic system for multiplexed and precalibrated expression of multigene pathways in fungi.

Synthetic biology requires efficient systems that support the well-coordinated co-expression of multiple genes. Here, we discover a 9-bp nucleotide sequence that enables efficient polycistronic gene expression in yeasts and filamentous fungi. Coupling polycistronic expression to multiplexed, markerless, CRISPR/Cas9-based genome editing, we develop a strategy termed HACKing (Highly efficient and Accessible system by CracKing genes into the genome) for the assembly of multigene pathways. HACKing allows the expression level of each enzyme to be precalibrated by linking their translation to those of host proteins with predetermined abundances under the desired fermentation conditions. We validate HACKing by rapidly constructing highly efficient Saccharomyces cerevisiae cell factories that express 13 biosynthetic genes, and produce model endogenous (1,090.41 ± 80.92 mg L-1 squalene) or heterologous (1.04 ± 0.02 mg L-1 mogrol) terpenoid products. Thus, HACKing addresses the need of synthetic biology for predictability, simplicity, scalability, and speed upon fungal pathway engineering for valuable metabolites.

Functional expansion of the natural inorganic phosphorus starvation response system in Escherichia coli.

Phosphorus, an indispensable nutrient, plays an essential role in cell composition, metabolism, and signal transduction. When inorganic phosphorus (Pi) is scarce, the Pi starvation response in E. coli is activated to increase phosphorus acquisition and drive the cells into a non-growing state to reduce phosphorus consumption. In the six decades of research history, the initiation, output, and shutdown processes of the Pi starvation response have been extensively studied. Simultaneously, Pi starvation has been used in biosensor development, recombinant protein production, and natural product biosynthesis. In this review, we focus on the output process and the applications of the Pi starvation response that have not been summarized before. Meanwhile, based on the current status of mechanistic studies and applications, we propose practical strategies to develop the natural Pi starvation response into a multifunctional and standardized regulatory system in four aspects, including response threshold, temporal expression, intensity range, and bifunctional regulation, which will contribute to its broader application in more fields such as industrial production, medical analysis, and environmental protection.

Establishing biosynthetic pathway for the production of p-hydroxyacetophenone and its glucoside in Escherichia coli.

p-Hydroxyacetophenone (p-HAP) and its glucoside picein are plant-derived natural products that have been extensively used in chemical, pharmaceutical and cosmetic industries owing to their antioxidant, antibacterial and antiseptic activities. However, the natural biosynthetic pathways for p-HAP and picein have yet been resolved so far, limiting their biosynthesis in microorganisms. In this study, we design and construct a biosynthetic pathway for de novo production of p-HAP and picein from glucose in E. coli. First, screening and characterizing pathway enzymes enable us to successfully establish functional biosynthetic pathway for p-HAP production. Then, the rate-limiting step in the pathway caused by a reversible alcohol dehydrogenase is completely eliminated by modulating intracellular redox cofactors. Subsequent host strain engineering via systematic increase of precursor supplies enables production enhancement of p-HAP with a titer of 1445.3 mg/L under fed-batch conditions. Finally, a novel p-HAP glucosyltransferase capable of generating picein from p-HAP is identified and characterized from a series of glycosyltransferases. On this basis, de novo biosynthesis of picein from glucose is achieved with a titer of 210.7 mg/L under fed-batch conditions. This work not only demonstrates a microbial platform for p-HAP and picein synthesis, but also represents a generalizable pathway design strategy to produce value-added compounds.