Food Waste-Assisted Metal Extraction from Printed Circuit Boards: The Aspergillus niger Route

Abstract

A low-energy paradigm was adopted for sustainable, affordable, and effective urban waste valorization. Here a new, eco-designed, solid-state fermentation process is presented to obtain some useful bio-products by recycling of different wastes. Urban food waste and scraps from trimmings were used as a substrate for the production of citric acid (CA) by solid state fermentation of Aspergillus niger NRRL 334, with a yield of 20.50 mg of CA per gram of substrate. The acid solution was used to extract metals from waste printed circuit boards (WPCBs), one of the most common electronic waste. The leaching activity of the biological solution is comparable to a commercial CA one. Sn and Fe were the most leached metals (404.09 and 67.99 mg/L, respectively), followed by Ni and Zn (4.55 and 1.92 mg/L) without any pre-treatments as usually performed. Commercial CA extracted Fe more efficiently than the organic one (123.46 vs. 67.99 mg/L); vice versa, biological organic CA recovered Ni better than commercial CA (4.55 vs. 1.54 mg/L). This is the first approach that allows the extraction of metals from WPCBs through CA produced by A. niger directly grown on waste material without any sugar supplement. This “green” process could be an alternative for the recovery of valuable metals such as Fe, Pb, and Ni from electronic waste.

It Works! Organic-Waste-Assisted Trichoderma spp. Solid-State Fermentation on Agricultural Digestate

“…Solid-state fermentation is a promising tool for the production of microorganism biomass, fungal biocontrol agents, and biostimulants. This technique offers several advantages to the bio-pesticides industries due to high fermentation productivity, low water and energy requirements, and the opportunity to use waste as a substrate [16,19,41].…”

“…SSF is a biotechnological process that better matches the natural physiology of microorganisms than liquid fermentation, involving growth on solid substrates in the absence or near absence of free water, low to zero shear stress, and direct contact with gas phases [16]. SSF has arisen as a sustainable method for the production of large amounts of either fungal biomass or secondary metabolites, such as bioactive compounds and organic acids [17][18][19][20][21], in the concept of circular processes. Moreover, it is less energy-demanding for the sterilization and pre-treatment of solid agro-industrial wastes and requires less water and produces less wastewater with consequently lower environmental impacts [14].…”

Screening of Cellulase Genes and Degrading Activities of Trichoderma Asperellum via Solid-State Fermentation of Rice Straw and Sugarcane Bagasse

“…Solid-state fermentation (SSF) is the fermentation of the solid waste in presence of little water (Prabhu et al, 2022). SSF is characterized with high cellulase levels with temperature constancy and low cost (Holker and Lenz, 2005;Singhania et al,2009;Saqib et al, 2010;Rahnama et al, 2013;Ávila et al, 2019;Perez et al, 2019;Alias et al, 2021).…”

Agro-Industrial Wastes: A Substrate for Multi-Enzymes Production by Cryphonectria parasitica

“…Agro-food wastes and by-products have been receiving growing attention as they are abundant [3], and rich in proteins, sugars and minerals which can be converted and assimilated by microorganisms [4]. One attractive valorization of agro-food wastes is their application in bio-refinery processes as substrates for microbial growth to produce various commodity chemicals and industrial enzymes [5][6][7].…”