Faculty of Agriculture, Department of Food Science and Technology, Shahrood University of Technology, Shahrood, Iran.
Faculty of Physics, Shahrood University of Technology, Shahrood, Iran.
Sci Rep. 2024 Nov 20;14(1):28718. doi: 10.1038/s41598-024-77465-9.
Heat-resistant fungal conidia are a common source of contamination and can cause significant difficulties in producing spawns. Through the use of PCR method, Aspergillus tubingensis and Aspergillus flavus as common microbial contaminants found in wheat grain spawn were identified that had been sterilized at 120 ºc for 2 h. Since these conidia are highly resistant to standard sterilization techniques, alternative methods were used to treat them with NaOCl and cold plasma and evaluate their effectiveness in reducing contamination. Optical emission spectroscopy (OES) analysis of the plasma showed dominant emissions from the N second positive system and N first negative system, while reactive oxygen species (ROS) spectral lines were undetected due to collision-induced quenching effects. Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray Spectroscopy (EDXS) analyses revealed notable alterations in the elemental makeup of conidia surfaces, as evidenced by a marked rise in levels of Na, O, Cl (in the case of NaOCl treatment) and N (in the case of plasma treatment). The conidia size was reduced at lower levels of NaOCl, but with increased concentrations and plasma treatment, the conidia underwent rupture and, in some cases, pulverization. The research suggests that utilizing a combined approach can be highly effective in eliminating heat-resistant fungal conidia and drastically cutting down the sterilization time for producing wheat spawn to only 30 s.
耐热真菌孢子是常见的污染来源，会给生产种菌带来很大的困难。通过使用 PCR 方法，鉴定出在 120°C 下经过 2 小时灭菌的麦粒种菌中存在的常见微生物污染物曲霉属管孢菌和黄曲霉。由于这些孢子对标准灭菌技术具有很强的抗性，因此使用了次氯酸钠和冷等离子体等替代方法对其进行处理，并评估了它们在减少污染方面的效果。等离子体的光发射光谱（OES）分析显示，N 第二正系统和 N 第一负系统的发射占主导地位，而由于碰撞诱导猝灭效应，未检测到活性氧（ROS）谱线。场发射扫描电子显微镜（FESEM）和能量色散 X 射线能谱（EDXS）分析表明，孢子表面的元素组成发生了显著变化，这表现在 Na、O、Cl（在次氯酸钠处理的情况下）和 N（在等离子体处理的情况下）的水平明显升高。在较低浓度的次氯酸钠处理下，孢子的大小会减小，但随着浓度的增加和等离子体处理，孢子会破裂，在某些情况下会粉碎。研究表明，采用组合方法可以非常有效地消除耐热真菌孢子，并将生产麦粒种菌的灭菌时间大幅缩短至 30 秒。
