Effective control of microbial spoilage in soybeans by water-soluble ZnO nanoparticles.

The microbial spoilage of soybeans during soaking process severely deteriorates the quality of soybean products and threatens human health. Herein, water-soluble aminated zinc oxide nanoparticles (ZnO NPs) were developed to effectively control the microbial spoilage in soybeans during soaking. ZnO NPs achieved significant inactivation of three dominant spoilage bacteria (bacillus cereus, bacillus megaterium and enterococcus faecium) isolated from the deteriorated soybeans, which could adhere to the bacterial surface and damage the cell wall/membrane, but also generate large amounts of reactive oxygen species (ROS). Compared to two commercial ZnO, water-soluble ZnO exhibited superior antibacterial properties due to producing more ROS and bacteria-adhered ability. After ZnO NPs treatment, the content of the residual Zn (51.1 mg/kg) in soybeans was the safety standards of Zn element in soybeans products for human). Therefore, the water-soluble ZnO NPs showed great potentials as efficient and safe antimicrobial agents for soybeans preservation during soaking process.

Hydrophilic ZnO Nanoparticles@Calcium Alginate Composite for Water Purification.

Herein, hydrophilic ZnO nanoparticles@calcium alginate composite has been prepared by embedding hydrophilic ZnO nanoparticles (NPs) into calcium alginate. The hydrophilic ZnO NPs within the composites can act as a killer of bacteria, while calcium alginate can remove the organic impurities due to its adsorption capacity, thus realizing the purification of water via sterilization and removal of organics. A water purifier based on the composite has been demonstrated, the aerobic bacterial counts of the contaminated water can be decreased from 2240 to 9 cfu mL-1, and the turbidity of the water is decreased to 0.51 NTU, which is below the maximum permissible of Guidelines for Drinking-water Quality designed by the World Health Organization. Sterilization mechanism studies show that the ZnO NPs can cause excessive oxidative stress in cells, inducing bacteria to produce large amounts of intracellular reactive oxygen species (ROS), which leads to the apoptosis of the bacteria.