Current understanding on antibacterial mechanisms and research progress of tea polyphenols as a supplementary disinfectant for drinking water

Resource utilization of tea waste in biochar and other areas: Current status, challenges and future prospects

The consumption of tea, one of the most popular non-alcoholic beverages, has steadily increased, leading to a significant rise in global tea production and consequently the generation of substantial amounts of tea waste annually. China alone generates more than 5 million tons of tea waste annually, comprising trimmed stems, discarded leaves and buds, waste from the manufacturing process, and residue after brewing. Tea is rich in polyphenols, polysaccharides, amino acids, alkaloids, and other active substances. Leveraging substantial quantities of tea waste can produce cost-effective derivatives across various sectors, thereby enhancing its utilitarian value and promoting a circular economy, for "Waste to Treasure". This study aims to evaluate the potential for resourceful utilization of tea waste in diverse applications. The current state of research concerning various applications of tea waste, including its use in biochar, composting feedstock, sludge performance modifiers, disinfection and biocides, as well as animal feed is comprehensively summarized. Focusing on the preparation and application of tea-waste-derived biochar (TWB), this study identifies several limitations in current TWB production technologies, including challenges related to performance, yield, and economic viability. Combined with bibliometric analysis, machine learning methods have emerged as valuable tools for evaluating and predicting biochar performance, as well as optimizing the biochar production process. An economic assessment of TWB production costs revealed that its production cost ($434.2/ton) is lower than that of corn stover ($454.19/ton) and wheat straw ($448.01/ton), but higher than rice straw ($425.73/ton). Furthermore, the analysis highlighted pyrolysis time and heating rate as critical factors influencing production costs, offering new insights compared to prior studies. This paper summarizes the progress and challenges faced by tea wastes in the field of biochar and looks at future directions. Results will provide sustainable utilization of tea waste and assist in exploiting this abundant and cheap waste biomass in many ways.

Formation mechanism of injured bacteria after disinfection with epigallocatechin gallate (EGCG) as a disinfectant

This study explored the effects of epigallocatechin gallate (EGCG), the main antibacterial component of tea polyphenols, on Escherichia coli in terms of disinfection damage and the underlying mechanisms. The researchers assessed inactivation and injury rates, cell morphology, and antioxidant indicators of E. coli when subjected to different concentrations of EGCG. The results showed that varying EGCG concentrations produced damaged bacteria, with the extent of damage depending on EGCG dosage and treatment duration. The disinfection process involving EGCG resulted in oxidative damage in E. coli, evoking alterations in the antioxidant system of the affected bacteria. During disinfection-induced bacterial injury, E. coli showed the active regulation of metabolism and redox activities in response to EGCG-induced environmental stimuli. Transcriptomic analysis was conducted to investigate the damage mechanism at the gene level. The damaged E. coli countered oxidative stress by adjusting gene expression related to peroxidase and glutathione metabolism processes. In this way, E. coli adjusts its gene expression to alleviate the detrimental effects of EGCG-induced oxidative stress and maintain cellular homeostasis. These findings contribute to our understanding of tea polyphenols' disinfection effects and provide insights into EGCG's mechanisms of damaging bacteria such as E. coli.

Restriction site-associated DNA sequencing (RAD-seq) of tea plant (Camellia sinensis) in Sichuan province, China, provides insights into free amino acid and polyphenol contents of tea

Worldwide, tea is a popular beverage; within the realm of Chinese tea, Sichuan tea holds particular significance for its role in the origin and composition of Chinese tea cultivars. Sichuan tea is noted for its rich content of free amino acids (FAAs) and tea polyphenols (TPs), which has made it an important subject for studying genetic diversity and the genes regulating these compounds. In this study, 139 varieties of tea were collected from areas in Sichuan Province, China, with similar geographical and climatic conditions. The FAA content was approximately 3% and the TP content was approximately 17%. Using RAD sequencing, 5,656,224 variant loci were identified, primarily comprising SNPs (94.17%) and indels (5.83%). Evolutionary analysis revealed that genetic divergence was not closely linked to the collection location. Population structure analysis confirmed a division into two main populations having a similar composition to the phylogenetic clusters. Screening for FAA-related SNPs identified significant loci associated with 33 genes that potentially regulate FAA content. Similarly, TP-related analysis pinpointed 8 SNPs significantly linked to 20 candidate genes. Notably, genetic associations hinted at the genes involved in the stress response and the accumulation of phenolic compounds, enhancing the understanding of determinants of tea quality. This research underscores the potential for molecular breeding based on genetic insights, suggesting pathways to improve the FAA and TP contents in tea. These findings not only provide a solid foundation for exploring gene-chemical interactions but also offer practical strategies for improving the nutritional and sensory attributes of tea cultivars through informed breeding practices.

Nanoparticles in drinking water: Assessing health risks and regulatory challenges

Nanoparticles (NPs) pose a significant concern in drinking water due to their potential health risks and environmental impact. This review provides a comprehensive analysis of the current understanding of NP sources and contamination in drinking water, focusing on health concerns, mitigation strategies, regulatory frameworks, and future perspectives. This review highlights the importance of nano-specific pathways, fate processes, health risks & toxicity, and the need for realistic toxicity assessments. Different NPs like titanium dioxide, silver, nanoplastics, nanoscale liquid crystal monomers, copper oxide, and others pose potential health risks through ingestion, inhalation, or dermal exposure, impacting organs and potentially leading to oxidative stress, inflammatory responses, DNA damage, cytotoxicity, disrupt intracellular energetic mechanisms, reactive oxygen species generation, respiratory and immune toxicity, and genotoxicity in humans. Utilizing case studies and literature reviews, we investigate the health risks associated with NPs in freshwater environments, emphasizing their relevance to drinking water quality. Various mitigation and treatment strategies, including filtration systems (e.g., reverse osmosis, and ultra/nano-filtration), adsorption processes, coagulation/flocculation, electrocoagulation, advanced oxidation processes, membrane distillation, and ultraviolet treatment, all of which demonstrate high removal efficiencies for NPs from drinking water. Regulatory frameworks and challenges for the production, applications, and disposal of NPs at both national and international levels are discussed, emphasizing the need for tailored regulations to address NP contamination and standardize safety testing and risk assessment practices. Looking ahead, this review underscores the necessity of advancing detection methods and nanomaterial-based treatment technologies while stressing the pivotal role of public awareness and tailored regulatory guidelines in upholding drinking water quality standards. This review emphasizes the urgency of addressing NP contamination in drinking water and provides insights into potential solutions and future research directions. Lastly, this review worth concluded with future recommendations on advanced analytical techniques and sensitive sensors for NP detection for safeguarding public health and policy implementations.

The interaction of polyphenols-polysaccharides and their applications: A review

Polyphenols, as important secondary metabolites in nature, are widely distributed in vegetables, fruits, grains, and other foods. Polyphenols have attracted widespread attention in the food industry and nutrition due to their unique structure and various biological activities. However, the health benefits of polyphenols are compromised owing to their structural instability and sensitivity to the external environment. The interaction between polyphenols and polysaccharides largely determined the stability and functional characteristics of polyphenols in food processing and storage. Thus, this topic has attracted widespread attention in recent years. The main purposes of this article are as follows: 1) to review the interaction mechanisms of polyphenols and polysaccharides including non-covalent and covalent bonds; 2) to comprehensively analyze the influencing factors of the interaction between polyphenols and polysaccharides, and introduce the effects of their interaction on the properties of polyphenols; 3) to systematically summarize the applications of interaction between polyphenols and polysaccharides. The findings can provide the important reference and theoretical support for the application of polyphenols and polysaccharides in food industry.

Valorizing Tea Waste: Green Synthesis of Iron Nanoparticles for Efficient Dye Removal from Water

This study explores the valorization of tea leaf waste by extracting polyphenols through reflux extraction, subsequently using them to synthesize zero-valent iron nanoparticles (nZVI). The in situ generated nanoparticles, when combined with fixed amounts of hydrogen peroxide, facilitated the removal of various dyes (methylene blue, methyl orange, and orange G) via a hetero-catalytic Fenton process. The iron nanoparticles were thoroughly characterized by gas adsorption of N2 at 77 K, scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), FT-IR spectroscopy, X-ray diffraction (XRD), and thermal analysis, including thermogravimetric analysis (TG) and temperature-programmed reduction (TPR). A statistical design of experiments and response surface methodology were employed to analyze the influence of polyphenol, Fe(III), and H2O2 concentrations on dye removal efficiency. The results demonstrated that optimizing the operational conditions could achieve 100% dye removal efficiency. This study highlights the potential of nZVI synthesized through eco-friendly methods as a promising solution for water decontamination involving diverse model dyes, thus contributing to sustainable waste management and environmental protection.

Study on the inactivation effect and mechanism of EGCG disinfectant on Bacillus subtilis

The widespread use of chlorine-based disinfectants in drinking water treatment has led to the proliferation of chlorine-resistant bacteria and the risk of disinfection byproducts (DBPs), posing a serious threat to public health. This study aims to explore the effectiveness and potential applications of epigallocatechin gallate (EGCG) against chlorine-resistant Bacillus and its spores in water, providing new insights for the control of chlorine-resistant bacteria and improving the biological stability of distribution systems. The inactivation effects of EGCG on Bacillus subtilis (B. subtilis) and its spores were investigated using transmission electron microscopy, ATP measurement, and transcriptome sequencing analysis to determine changes in surface structure, energy metabolism, and gene expression levels, thereby elucidating the inactivation mechanism. The results demonstrate the potential application of EGCG in continuously inhibiting chlorine-resistant B. subtilis in water, effectively improving the biological stability of the distribution system. However, EGCG is not suitable for treating raw water with high spore content and is more suitable as a supplementary disinfectant for processes with strong spore removal capabilities, such as ozone, ultraviolet, or ultrafiltration. EGCG exhibits a disruptive effect on the morphological structure and energy metabolism of B. subtilis and suppresses the synthesis of substances, energy metabolism, and normal operation of the antioxidant system by inhibiting the expression of multiple genes, thereby achieving the inactivation of B. subtilis.

Gelatin based preservation technologies on the quality of food: a comprehensive review

Gelatin has played a great potential in food preservation because of its low price and superior film forming characteristics. This review provides a comprehensive overview of the latest research progress and application of gelatin preservation technologies (film, coating, antifreeze peptide, etc.), discussing their preservation mechanisms and efficiency through the viewpoints of quality and shelf life of animal and aquatic products as well as fruits and vegetables. It showed that bioactive and intelligent gelatin-based films exhibit antibacterial, antioxidant, water resistance and pH responsive properties, making them excellent for food preservation. In addition, pH responsive properties of films also intuitively reflect the freshness of food by color. Similarly, gelatin and its hydrolysate can be widely used in antifreeze peptides to reduce the mass loss of food during freezing and extend the shelf life of frozen food. However, extensive works are still required to extend their commercial application values.

Shelf-life extension of soy sauce by using chitosan oligosaccharides combined with tea polyphenols

Chitosan oligosaccharides (COs) and tea polyphenols (TPs) have antioxidant and antibacterial activities. This study aims to explore the preservative effects of 0.1 % COs alone and combined with 0.08 % TPs on soy sauce during room-temperature storage. Soy sauce treated with 0.1 % COs alone and combined with 0.08 % TPs had lower total bacterial count, Escherichia coli count and pH, and higher amino acid nitrogen and overall likeness score than those of the control group during room-temperature storage. Treatment with 0.1 % COs combined with 0.08 % TPs extended the shelf life of soy sauce by at least 15 months compared with the control group. Results showed 0.1 % COs combined with 0.08 % TPs may be a feasible method to extend the shelf life of soy sauce during room-temperature storage.

Characterization of tea (Camellia sinensis L.) flower extract and insights into its antifungal susceptibilities of Aspergillus flavus

BACKGROUND

Tea (Camellia sinensis L.) flowers will compete with tea leaves in nutrition and are abandoned as an undesirable by-product. In this study, the biological efficacy of tea flowers was investigated. Further exploration of its antifungal activity was explained.

METHODS

Tea flowers harvested from China were characterized in term of component, antioxidant ability, tyrosinase inhibition, and antifungal ability. Chemical compounds of tea flowers were analyzed by LC-MS. Disinfectant compounds were identified in tea flowers, and 2-ketobutyric acid exhibited antifungal activity against Aspergillus flavusCCTCC AF 2023038. The antifungal mechanism of 2-ketobutyric acid was further investigated by RNA-seq.

RESULTS

Water-soluble tea flower extracts (TFEs) exhibited free radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) as well as a high ferric-reducing ability. However, no inhibition of tyrosinase activity was observed. In the antifungal test, 6.4 mg/mL TFE reached 71.5% antifungal rate and the electrical conductivity of the culture broth increased with increasing concentration of TFE, implying that it damaged the fungal cell membrane by the TFE. Several disinfectants were identified in TFE by LC-MS, and 2-ketobutyric acid was also confirmed to be capable of fungal inhibition. Propidium iodide (PI) staining indicated that 2-ketobutyric acid caused damage to the cell membrane. RNA-seq analysis revealed that 3,808 differentially expressed genes (DEGs) were found in A. flavus CCTCC AF 2023038 treated by 2-ketobutyric acid, and more than 1,000 DEGs involved in the integral and intrinsic component of membrane were affected. Moreover, 2-ketobutyric acid downregulated aflatoxin biosynthesis genes and decreased the aflatoxin production.

CONCLUSIONS

Overall, TFE exhibited excellent antioxidant ability and fungal inhibition against A. flavus CCTCC AF 2023038 due to its abundant disinfectant compounds. As a recognized food additive, 2-ketobutyric acid is safe to use in the food industry and can be utilized as the basis for the research and development of strong fungicides.

Combined Catalysis: A Powerful Strategy for Engineering Multifunctional Sustainable Lignin-Based Materials

The production and engineering of sustainable materials through green chemistry will have a major role in our mission of transitioning to a more sustainable society. Here, combined catalysis, which is the integration of two or more catalytic cycles or activation modes, provides innovative chemical reactions and material properties efficiently, whereas the single catalytic cycle or activation mode alone fails in promoting a successful reaction. Polyphenolic lignin with its distinctive structural functions acts as an important template to create materials with versatile properties, such as being tough, antimicrobial, self-healing, adhesive, and environmentally adaptable. Sustainable lignin-based materials are generated by merging the catalytic cycle of the quinone-catechol redox reaction with free radical polymerization or oxidative decarboxylation reaction, which explores a wide range of metallic nanoparticles and metal ions as the catalysts. In this review, we present the recent work on engineering lignin-based multifunctional materials devised through combined catalysis. Despite the fruitful employment of this concept to material design and the fact that engineering has provided multifaceted materials able to solve a broad spectrum of challenges, we envision further exploration and expansion of this important concept in material science beyond the catalytic processes mentioned above. This could be accomplished by taking inspiration from organic synthesis where this concept has been successfully developed and implemented.