Chemical‐ vs sonochemical‐assisted synthesis of ZnO nanoparticles from a new zinc complex for improvement of carotene biosynthesis from Rhodotorula toruloides MH023518

The complex [ZnL2] {HL = 2-(((3,4-dimethylphenyl)imino)methyl)phenol} was introduced by two routes (chemical vs. sonochemical) and acted as a source of different size zinc-oxide (ZnO) nanoparticles (NPs) (nonsonicated ZnO NPs of Brunauer–Emmett–Teller (BET) surface area of 19.208 m2 g−1, total pore volume of 0.03493 cc g−1, and particle diameter of 20.49–114.89 nm vs. sonicated ZnO NPs of BET surface area of 38.383 m2 g−1, total pore volume of 0.08723 cc g−1 and particle diameter of 15.09–55.31 nm). The NPs generate cell stress that leads to the formation of reactive oxygen species (ROS). Consequently, carotene biosynthesis can be enhanced to overcome the ROS. Rhodotorula toruloides MH023518, genetically identified with 18S rRNA, produced carotenoids (124 ± 4.5 mg L−1) and lipids (0.897 ± 0.01 mg L−1) under no NPs' stress, but these values increased to total carotenoids of 264 ± 0.6 and 297.78 ± 0.8 mg L−1 and total lipids of 0.97 ± 0.007 and 1.096 ± 0.015 mg L−1 under stress conditions of 50 ppm of the nonsonicated and sonicated ZnO NPs, respectively. These results may represent potential industrial utilization of the as-formed ZnO NPs (particularly the sonicated sample) as carotene and lipid stimulator. Additionally in this article, the soluble proteins, total antioxidants, and catalase and superoxide dismutase specific activities of the yeast in the presence of various concentrations of the as-formed ZnO NPs were determined.