分子拥挤增强DNA-AgNCs的抗真菌能力及其在柑橘保鲜中的应用

杜宁; 陈旭; 刘海燕; 许文涛

doi:10.13386/j.issn1002-0306.2022030350

分子拥挤增强DNA-AgNCs的抗真菌能力及其在柑橘保鲜中的应用

Antifungal Ability of DNA-AgNCs under Molecular Crowding and Its Application in Citrus Preservation

摘要

摘要: 为探究分子拥挤对DNA-AgNCs抗真菌能力的影响及其对柑橘的保鲜作用，本实验先将DNA序列（5'-CCCCCCCCCCCC-3'）与AgNO₃溶液混合，以50%聚乙二醇（Polyethylene Glycol，PEG）200溶液模拟分子拥挤环境，制备DNA-AgNCs。以DNA-AgNCs为研究对象，以扩展青霉、黄曲霉、禾谷镰刀菌、串珠镰刀菌为模型，以孢子计数法测定DNA-AgNCs对四种孢子萌发的抑制率，用微量稀释法确定DNA-AgNCs对四种真菌的最低抑菌浓度（Minimal Inhibitory Concentration，MIC）。将DNA-AgNCs加入淀粉-壳聚糖基质中制备复合薄膜，通过拉伸实验、水接触角和抑菌圈实验探究其对薄膜力学性能、疏水性和抗菌性的影响，以涂膜的形式应用到柑橘保鲜，记录柑橘失重率、菌斑直径和感官评价。结果表明：分子拥挤DNA-AgNCs对孢子萌发的抑制作用优于正常DNA-AgNCs（P<0.05），MIC均在2.5 μmol/L内；加入分子拥挤DNA-AgNCs的薄膜的拉伸性能由4.729 MPa增加至7.300 MPa，断裂伸长率由51.399%增加至77.287%，水接触角由59.700°增加至66.717°，对四种真菌的抑菌圈分别为23.969、19.176、16.822和13.349 cm；将柑橘在添加分子拥挤DNA-AgNCs溶液中浸泡涂膜，于28 ℃贮藏14 d，失重率（23.8%）和病斑直径（2.3 cm）显著低于对照组（P<0.05），感官评价（52分）显著高于对照组（P<0.05）。因此，分子拥挤能够增强DNA-AgNCs的抗菌能力，所制得涂膜能很好地保持柑橘的贮藏品质。

Abstract: In order to investigate the effect of molecular crowding on the antifungal ability of DNA-AgNCs and its preservation effect on citrus, DNA sequence (5'-CCCCCCCCCCCC-3') was mixed with AgNO₃ solution in this experiment. DNA-AgNCs was prepared by simulating molecular crowded environment with 50% Polyethylene Glycol (PEG) 200 solution. Taking DNA-AgNCs as the research object, using Penicillium expansum, Aspergillus flavus, Fusarium graminaerum and Fusarium moniliforme as the models, the inhibition rate of DNA-AgNCs on the germination of four kinds of spores was determined by spore counting method, and the Minimal Inhibitory Concentration (MIC) of DNA-AgNCs against four kinds of fungi was determined by microdilution method. DNA-AgNCs was added to starch-chitosan matrix to prepare composite films, and its effects on the mechanical properties, hydrophobicity and antibacterial properties of the films were explored through tensile test, water contact angle and inhibition zone test. The film was applied to citrus preservation in the form of coating film, and the weight loss rate, plaque diameter and sensory evaluation of citrus were recorded. The results showed that the inhibitory effect of molecular crowded DNA-AgNCs on spore germination was better than that of normal DNA-AgNCs (P<0.05), and the MIC was within 2.5 μmol/L. The tensile properties of the films with molecular crowded DNA-AgNCs increased from 4.729 to 7.300 MPa, the elongation at break increased from 51.399% to 77.287%, and the water contact angle increased from 59.700° to 66.717°. The inhibition zones of the four fungi were 23.969, 19.176, 16.822 and 13.349 cm, respectively. When citrus was soaked and coated in the solution supplemented with molecular crowded DNA-AgNCs and stored at 28 ℃ for 14 d, the weight loss rate (23.8%) and plaque diameter (2.3 cm) were significantly lower than those of the control group (P<0.05), and the sensory evaluation (52 points) was significantly higher than that of the control group (P<0.05). In conclusion, molecular crowding could enhance the antibacterial ability of DNA-AgNCs, and the coating film could well maintain the storage quality of citrus.