Abstract In this study, melon peel waste was utilized to isolate peroxidase enzyme through three-phase portioning (TPP) and subsequently immobilized onto magnetite nanoparticles for effective bioremediation of phenol pollutants from water. The optimization of TPP parameters ensured maximum activity recovery and enzyme purity. Magnetite nanoparticles were synthesized and used as a substrate for immobilizing the isolated peroxidase, achieving an activity recovery of 157% and a purification fold of 5.2. Protein homogeneity testing confirmed the purity of the peroxidase enzyme. The magnetite nanoparticles had an average diameter of 62 nm, and the immobilization efficiency reached 93% at pH 8 with an enzyme/nanoparticles v/v ratio of 1:9. The immobilized peroxidase demonstrated the ability to degrade 57% of phenol within 3 h and retained 30% relative activity even after five catalytic cycles. This immobilized melon peel peroxidase on magnetite nanoparticles proves to be a robust, enduring, and reusable biocatalyst with potential for various applications, especially in bioremediation processes. Graphical Abstract

Foodborne bacterial infection poses a serious threat to human health. As most diseases are caused by living bacteria, real-time assessment of bacterial viability is vitally important to the public health sector. Herein, we developed a simple and novel colorimetric assay based on the Glucose oxidase (GOD)/Horseradish peroxidase (HRP) bienzyme system for real-time monitoring of bacterial viability in food and drinking water. This bienzyme system is free of any chemical synthesis and only requires 3 sample handling steps. The color response is easily observable with the naked eye or recordable with a smartphone for precise determination of bacterial viability. The proposed strategy was validated with various bacteria both Gram-positive and Gram-negative, indicating its capability for broad-spectrum bacteria viability detection. Therefore, the proposed strategy shows promise for rapid and reliable quality control in food and drinking water.

Previous studies have confirmed that electrolyzed water had disinfection potential and enrich functional nutrients during seed germination. However, the effect of slightly acidic electrolyzed water (SAEW) on the quality and safety of peanut sprouts is poorly understood. In this study, the influence and mechanism of SAEW on the antibacterial, antioxidant capacity, and allergenicity of peanut sprouts were investigated. Although SAEW‐3 with 33.85 mg/L available chlorine concentration (ACC) showed better antibacterial effect, the SAEW‐2 (23.74 mg/L ACC) group has a 20% and 50% increase in phenolic acid and γ‐aminobutyric acid content, respectively. Moreover, SAEW‐2 induced peanut sprout has the best antioxidant capacity by eliminating free radicals and improving peroxidase activity. SAEW‐2 or SAEW‐3 treatment contributed to decreasing Ara h 1 and Ara h 2 content thus reduce allergenicity. Therefore, SAEW with appropriate ACC could be a promising application in food safety, nutrients enrichment, and health‐improvement of peanut products. NOVELTY IMPACT STATEMENT: Slightly acidic electrolyzed water (SAEW) with 23.74 mg/L available chlorine concentration (ACC) has a significant positive effect on the enrichment of phenolic and γ‐aminobutyric acid in germinated peanut. With the help of SAEW, the germination process can further reduce the content of Ara h 1 and Ara h 2, thereby reducing allergenicity. SAEW with appropriate ACC could be a promising application in food safety, nutrients enrichment, and health‐improvement of peanut products.

It is well known that immune defenses of bivalves against environmental and pathogenic stresses are primarily attributable to hemocytes. Hemocyte parameters are being used progressively as indicators to assess the host immune status. Moreover, there is increasing evidence that seasonal variations on the immune status have two origins: exogenous and endogenous. In this work, we investigated the effects of seasonal exogenous (water temperature and food availability) and endogenous (size and reproduction) factors on the hemocyte parameters in the scallop Chlamys farreri. Scallops were monthly collected from February to December 2009 at 2 sampling sites differing in culture mode: Qingdao for monoculture and Weihai for scallop—kelp polyculture. Six hemocyte parameters including total hemocyte count (THC), granulocyte percentage (GP), intrahemocytic phenoloxidase (PO), acid phosphatase (ACP), superoxide dismutase (SOD), and peroxidase (POD) were analyzed. Results illustrated that all hemocyte parameters exhibited marked seasonal variations, following a similar pattern at both sites. High values of THC, GP, PO, and POD were observed in spring and early summer, a period of favorable water temperature and high food availability and gonad index, whereas low values were found in summer and early autumn, a period corresponding to reproduction completion and high water temperature. Moreover, SOD was lowest in February and highest in August, and correlated positively with water temperature. Hemocyte parameters in the scallop C. farreri varied greatly among seasons, and their values were generally low during summer and early autumn, suggesting that scallops had a depressed immune status during this period.

Evaluation of acetylcholinesterase (AChE) activity and determination of organophosphorus pesticides (OPs) are of great importance for the clinical diagnosis of several serious diseases correlated with their variations in human blood serum. In this study, a highly selective and sensitive ratiometric fluorescent probe was innovatively fabricated for the evaluation of AChE activity and the determination of OPs in tap water and food on the basis of the inner filter effect (IFE) between nitrogen-doped carbon dots (N-CDs) and 2,3-diaminophenazine (DAP). N-CDs were synthesized via a one-pot hydrothermal method by using pancreatin and 1,2-ethanediamine as precursors. N-CDs showed excellent fluorescence properties and negligible cytotoxicity on human cervical carcinoma HeLa cells and human embryonic kidney 293T cells, suggesting their further biological applications. Upon the addition of AChE and choline oxidase, acetylcholine was catalyzed to produce choline that was further oxidized to produce H₂O₂. In the presence of horseradish peroxidase, o-phenylenediamine reacted with H₂O₂ to produce fluorescent DAP. Therefore, a ratiometric fluorescent probing platform existed via IFE between N-CDs with a fluorescence signal at 450 nm and DAP with a fluorescence signal at 574 nm. OPs irreversibly impeded the catalytic activity of AChE, finally leading to the decrease of DAP amount and the variation of ratiometric fluorescent signal. Under optimal conditions, such a fluorescent probe showed relatively low detection limits of 0.38 U/L for AChE, 3.2 ppb for dichlorvos, and 13 ppb for methyl-parathion. Practical application of this ratiometric fluorescent probe to detect OPs was further verified in tap water and food samples with satisfying results that were highly consisted with the results obtained by GC–MS.