Microbial fermentation-based synthesis of nano-curcumin suggesting the role of pullulan in nano-formulation

Curcumin is a multitargeting nutraceutical with numerous health benefits, however, its efficacy is limited due to poor aqueous solubility and reduced bioavailability. While nano-formulation has emerged as an alternative to encounter such issues, it often involves use of toxic solvents. Microbial synthesis may be an innovative solution to address this lacuna. Present study, for the first time, reports exploitation of Aureobasidium pullulans RBF4A3 for production of nano-curcumin. For this purpose, Aureobasidium pullulans RBF4A3 was inoculated in YPD media along with curcumin (0.1 mg/mL) and incubated for 24 h, 48 h, and 72 h. Subsequently, residual sugar, biomass, EPS concentration, curcumin concentration, and curcumin nanoparticle size were measured. As a result, nano-curcumin with an average particle size of 31.63 nm and enhanced aqueous solubility was obtained after 72 h. Further, investigations suggested that pullulan, a reducing polysaccharide, played a significant role in curcumin nano-formulation. Pullulan-mediated nano-curcumin formulation, with an average particle size of 24 nm was achieved with conversion rate of around 59.19 %, suggesting improved aqueous solubility. Additionally, the anti-oxidant assay of the resulting nano-curcumin was around 53.7 % per μg. Moreover, kinetics and thermodynamic studies of pullulan-based nano-curcumin revealed that it followed first-order kinetics and was favored by elevated temperature for efficient bio-conversion. Also, various physico-chemical investigations like FT-IR, NMR, and XRD reveal that pullulan backbone remains intact while forming curcumin nanoparticle. This study may open up new avenues for synthesizing nano-polyphenols through a completely green and solvent free process with plausible diverse applications.