• UP treatment was effective in microbial decontamination of crayfish. • The applied treatments suppressed the protein oxidation during storage. • UP treatment retarded the flavor and textural deterioration of crayfish. • UP treatment reduced the water migration in crayfish during storage.

This study investigated changes in the microbial compositions of crayfish tails during storage at 4 °C (for 0–12 days) as measured using high-throughput sequencing (HTS). The specific spoilage organisms (SSOs) in the crayfish tails were isolated using culture-dependent cultivation methods, and they were identified by 16S rRNA and characterized for their enzymatic spoilage potentials (e.g., protease, lipase, phospholipase, and amylase). The spoilage abilities of the selected strains in the crayfish tails were assessed by inoculating them into real food. Moreover, the microbial growth and the volatile basic nitrogen (TVB-N) changes were monitored during the storage period. The results from the HTS showed that the dominant genus of shrimp tails evolved from Streptococcus (D0) to Pseudomonas (D4) and, finally, to Paenisporosarcina (D12) during storage. Seven bacterial species (Acinetobacter lwoffii, Aeromonas veronii, Kurthia gibsonii, Pseudomonas sp., Exiguobacterium aurantiacum, Lelliottia amnigena, and Citrobacter freundii) were screened from the spoiled shrimp tails by the culture-dependent method, among which Aeromonas veronii had the strongest spoilage ability.

In recent years, the impacts of global warming, including glacial melting, extreme weather events, food crises, and epidemics, have become increasingly severe, posing significant challenges to global sustainability. The primary driver of the current climate crisis is the substantial emission of greenhouse gases (GHGs), particularly carbon dioxide (CO₂). Microalgae, as photoautotrophic microorganisms, offer a promising solution by utilizing CO₂ for biosynthesis. Previous research indicates that microalgae can fix CO₂ at rates exceeding 1.5 kg/m²/year under optimal conditions, and produce lipids with high content of unsaturated fatty acids. This review delves into recent advancements understanding the causes and effects of global warming, with a particular focus on agricultural GHG emissions. It critically examines the carbon sequestration mechanisms of microalgae and their potential as single-cell biofactories for carbon neutralization and biomanufacturing. The review highlights their ability to fix CO₂ and produce high-value products such as biofuels, chemicals, pharmaceuticals, and foods. Among these species, the characteristics and value of seven edible microalgae are also described. We outline the technical and economic challenges associated with scaling up microalgae cultivation from laboratory to industrial scale, including the optimization of cultivation systems and the improvement of harvesting and processing techniques. This review serves as a useful and informative reference for the application of CO₂ capture and high-value bioproducts by microalgae, aiming to provide a reference for the realization of carbon neutrality and the mitigation of climate change.

Introduction: Carbon quantum dots (CQDs) are a promising class of zero-dimensional carbon nanomaterials (<10 nm) that can be synthesized from organic precursors. They have attracted intense attentions due to their high water solubility, nontoxicity, excellent biocompatibility, and strong optical properties. Microalgae offer a low-cost, renewable, and eco-friendly source of carbon for CQD synthesis. Their high carbon content, functionalization potential, and biocompatibility make them ideal precursors for producing CQDs with excellent properties and versatile applications. Methods: In this study, we explored the synthesis of Euglena gracilis -derived CQDs (E-CQDs) via a one-step hydrothermal green synthesis method and investigated their potential application in bioimaging and antibacterial materials. The synthesized E-CQDs were comprehensively characterized using TEM, XRD, FTIR, XPS, and UV-vis analysis. Results: The TEM images showed that E-CQDs had a spherical shape with diameters ranging from 6.5 to 10.5 nm. The XRD patterns indicated that the E-CQDs were crystalline in nature. The FTIR results suggested that E-CQDs were functionalized with C-N and N-H bonds. XPS analysis showed that the E-CQDs were mainly composed of carbon,nitrogen, oxygen and silicon. The UV-vis spectra exhibited a peak at a wavelength of 252 nm, indicating strong absorption in the ultraviolet region. The antibacterial activity test demonstrated that E-CQDs had high inhibitory activity against Escherichia coli and Staphylococcus aureus, causing damage to their cell membranes. Additionally, the bioimaging assay indicated E-CQDs possessed the capacity for bioimaging applications in cells, such as Chlorella. Discussion: This work presents a green synthesis approach for microalgae-derived CQDs, overcoming some environmental drawbacks of traditional chemical methods. It validates the dual-function paradigm where a single nanomaterial can simultaneously suppress bacterial growth and enable bioimaging.

Aeromonas veronii is a foodborne pathogen commonly found in contaminated crayfish. In this study, the effects of ultrasound combined with plasma-activated water (US-PAW) against A. veronii and on the flavour of crayfish were investigated to evaluate their impact on crayfish preservation. In vitro, US and PAW showed a significantly synergistic inhibition against A. veronii growth and biofilm reformation at 7 min. Furthermore, PAW disrupted the membrane integrity of A. veronii, accompanied by enhanced outer membrane permeability, with bacteria exhibiting distortion, deformation, and the accelerated leakage of intracellular substances, which US-PAW further promoted. Additionally, US-PAW increased the intracellular levels of reactive oxygen species and hydrogen peroxide, disrupting cellular homeostasis. This resulted in a significant decrease in the activities of SOD and GSH, as well as a reduction in the intracellular ATP concentration and the activities of MDH and SDH. The results indicated that US-PAW treatment impairs the ability of A. veronii cells to generate sufficient energy to resist external stress, ultimately leading to bacterial death due to the inability to maintain normal physiological functions. According to the bacterial cell count and GC-MS analysed, US-PAW treatment increased the storage period of crayfish (infected with A. veronii) by 2 days, while reducing sulphur-containing volatiles within 24.64% during 6 days of storage at 4 °C. These conclusions provide a theoretical foundation for the industrial application of US-PAW to preserve crayfish.