Valorization of Pichia spent medium via one-pot synthesis of biocompatible silver nanoparticles with potent antioxidant, antimicrobial, tyrosinase inhibitory and reusable catalytic activities.

Abstract

The purpose of this study was to determine the feasibility of a novel biogenic synthesis of silver nanoparticles using Pichia pastoris spent medium - a major waste product from heterologous protein expression as the sole reducing and capping agent, with potential biological, antimicrobial and wastewater remediation applications. Using UV-vis spectroscopy, TEM, XRD, EDX, FTIR, SEM we demonstrated the successful bio-fabrication of Pichia spent medium encapsulated silver nanoparticles (PSM-AgNPs). PSM-AgNPs displayed substantial antiradical activity against DPPH and ABTS. The antiradical activity against ABTS was similar to that of the control, ascorbic acid. PSM-AgNPs also revealed potent anti-tyrosinase and antibacterial activity against some common foodborne pathogenic microbes. Human erythrocyte hemolytic and embryonic colon Caco-2 cell viability assays suggest that PSM-AgNPs was biocompatible. In addition, PSM-AgNPs, was also effective in the catalytic degradation of methyl orange and Congo red dyes with pseudo first order rate constants of 0.2301min-1 and 4.7×10-3s-1, respectively. These results present a clean, convenient, and inexpensive approach for the biosynthesis of silver nanoparticles with potential implications in the eco-friendly, safe and effective utilization of waste culture media, mitigation of pathogenic bacteria and management of industrial effluents.