Egyptian Petroleum Research Institute, Cairo, Egypt.
Faculty of Science, Ain Shams University, Cairo, Egypt.
J Appl Microbiol. 2019 Jan;126(1):138-154. doi: 10.1111/jam.14102. Epub 2018 Oct 9.
In order to efficiently control the corrosive sulphate-reducing bacteria (SRB), the main precursor of the microbial influenced corrosion (MIC) in oil industry, the ability of Trichoderma longibrachiatumDSMZ 16517 to synthesize silver nanoparticles (AgNPs) was investigated and their biocidal activity against halotolerant SRB was tested.
The mycelial cell-free filtrate (MCFF) bioreduced the silver ions (Ag ) to their metallic nanoparticle state (Ag ), which was presumptively indicated by the appearance of a dark brown suspension and confirmed by the characteristic absorbance of AgNPs at ʎ . One-factor-at-a-time technique was used to optimize the effect of temperature, time, pH, fungal biomass and silver nitrate concentrations, stirring rates and dark effect. The dynamic light scattering (DLS) analysis revealed average AgNPs size and zeta potential values of 17·75 nm and -26·8 mV, respectively, indicating the stability of the prepared AgNPs. The X-ray diffraction (XRD) pattern assured the crystallinity of the mycosynthesized AgNPs, with an average size of 61 nm. The field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM) showed nonagglomerated spherical, triangular and cuboid AgNPs ranging from 5 to 11 ± 0·5 nm. The Fourier transform infrared spectroscopy (FT-IR) analysis of the mycosynthesized AgNPs affirmed the role of MCFF as a reducing and capping agent. A preliminary suggested mechanism for mycosynthesis of AgNPs was elucidated. The mycosynthesized AgNPs expressed high biocidal activity against a halotolerant planktonic mixed culture of SRB. The HRTEM analysis showed a clear evidence of an alteration in cell morphology, a disruption of SRB cell membranes, a lysis in cell wall and a cytoplasmic extraction after treatment with AgNPs. This confirmed the bactericidal effect of the mycosynthesized AgNPs.
The biocidal activity of the mycosynthesized AgNPs against halotolerant planktonic SRB makes it an attractive option to control MIC in the petroleum industry.
This research provides a helpful insight into the development of a new mycosynthesized biocidal agent against the corrosive sulphate-reducing bacteria.
为了有效控制腐蚀性硫酸盐还原菌（SRB），这种微生物影响腐蚀（MIC）在石油工业中的主要前体，研究了长枝木霉 DSMZ 16517 合成银纳米粒子（AgNPs）的能力，并测试了其对耐盐硫酸盐还原菌的杀菌活性。
菌丝体无细胞滤液（MCFF）将银离子（Ag + ）还原成其金属纳米颗粒状态（Ag 0 ），这可以通过暗褐色悬浮液的出现来推测，并通过 AgNPs 的特征吸收来证实 在 ʎ 处。单因素试验技术用于优化温度、时间、pH 值、真菌生物量和硝酸银浓度、搅拌速度和暗效的影响。动态光散射（DLS）分析表明，制备的 AgNPs 的平均粒径和 Zeta 电位值分别为 17.75nm 和-26.8mV，表明制备的 AgNPs 稳定。X 射线衍射（XRD）图谱保证了所合成的 AgNPs 的结晶度，平均粒径为 61nm。场发射扫描电子显微镜（FESEM）和高分辨率透射电子显微镜（HRTEM）显示，非团聚的球形、三角形和立方 AgNPs 的粒径范围为 5-11nm±0.5nm。银纳米粒子的傅里叶变换红外光谱（FT-IR）分析证实了 MCFF 作为还原剂和封端剂的作用。阐明了真菌合成 AgNPs 的初步建议机制。真菌合成的 AgNPs 对耐盐浮游混合硫酸盐还原菌表现出很高的杀菌活性。HRTEM 分析显示，在用 AgNPs 处理后，细胞形态发生明显变化，SRB 细胞膜破裂，细胞壁裂解，细胞质提取，证实了真菌合成的 AgNPs 的杀菌效果。
真菌合成的 AgNPs 对耐盐浮游硫酸盐还原菌的杀菌活性使其成为控制石油工业中 MIC 的一种有吸引力的选择。
这项研究为开发一种新的抗腐蚀性硫酸盐还原菌的真菌合成杀菌剂提供了有益的见解。
