Fungi Emerge as Sustainable Factories for Advanced Nanomaterial Production

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• Fungi offer a sustainable alternative to toxic chemical synthesis methods for producing nanomaterials, acting as natural reducing and capping agents whilst demonstrating high metal tolerance and ease of cultivation at scale.

• Myconanotechnology can produce diverse nanomaterials including metal nanoparticles, quantum dots, and nanocomposites with sizes ranging from 1-100 nm, each exhibiting unique properties dependent on fungal species and culture conditions.

• Despite environmental benefits, mycogenic nanomaterials face significant challenges including strain-dependent variability, batch-to-batch inconsistency, and the need for comprehensive regulatory frameworks to address potential toxicity concerns.

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Based on research by Parikshana Mathur and Santhosh Pillai from the Department of Biotechnology and Food Science, Durban University of Technology, published in Fungal Biology Reviews (2025).

In a South African laboratory, researchers are harnessing the metabolic machinery of fungi to produce nanomaterials through myconanotechnology. This biological approach hopes to revolutionise how we synthesise the tiny particles that power everything from medical treatments to environmental remediation.

Traditional nanotechnology relies heavily on harsh chemicals and extreme temperatures, creating environmental concerns and driving up costs. Physical synthesis methods require "high-temperature and pressure control" whilst chemical approaches demand "excessive chemical usage" and "additional purification steps," according to Mathur and Pillai's research. These limitations have prompted exploration of biological alternatives, with fungi emerging as particularly promising candidates.

Aspergillus niger. Credits: Picassa

The Fungal Advantage

Fungi possess several characteristics that make them ideal for nanomaterial synthesis. Unlike other microorganisms, they demonstrate exceptional "high metal tolerance, ease of growth, and ease in the management of biomass." Their cellular machinery naturally produces enzymes, proteins, and metabolites that function as both reducing agents—converting metal salts into nanoparticles—and capping agents that prevent particle aggregation.

The process occurs through two primary routes. In extracellular synthesis, "fungal filtrate containing various metabolites undergo reactions that reduce the metal salt solution, resulting in nanoparticles." This method proves more commercially viable than intracellular synthesis, which requires "tedious downstream processing leading to increased production costs."

Filamentous fungi offer particular advantages for large-scale production. Their branched networks provide "a larger surface area and release more proteins and metabolites for metal ion reduction" whilst creating "an efficient template for nanomaterial formation, providing various metal-binding functional groups."

A Spectrum of Possibilities

Myconanotechnology can produce an impressive range of materials. Metal nanoparticles synthesised through fungal processes include silver particles from Penicillium citrinum and Trichoderma harzianum, gold nanoparticles from Colletotrichum sp., and iron oxide particles from Aspergillus niger. These particles demonstrate remarkable diversity in size—ranging from 2-4 nm to 100-1000 nm—and morphology.

Quantum dots represent another frontier. These semiconductor nanocrystals, measuring between 1.5 and 10 nm, exhibit "strong fluorescence, pH sensitivity, and conductivity." Fungal species such as Fusarium oxysporum and Rhodotorula mucilaginosa have successfully produced cadmium selenide and cadmium sulphide quantum dots with "intense absorbance and fluorescence" properties.

Fungi can also create nanocomposites—hybrid materials combining nanoparticles with biological matrices. These materials demonstrate enhanced properties including "improved absorption capacity" for radioactive materials and enhanced antimicrobial effects.

Credits: Parikshana Mathur and Santhosh Pillai

The Variables That Matter

The success of mycogenic synthesis depends on numerous interrelated factors. Fungal strain selection proves critical, as "different species and genera have varying capacities to interact with and reduce metal precursors." Culture conditions—including pH, temperature, nutrient availability, and substrate composition—significantly influence particle size, shape, and stability.

Temperature effects prove particularly notable. Studies show optimal conditions ranging from 25°C for some Aspergillus fumigatus applications to 60°C for certain Fusarium oxysporum processes. Similarly, alkaline pH conditions generally promote "more stable and monodispersed" particles.

Metal salt concentration presents another crucial variable. Research indicates that "low concentrations slow down the synthesis process while higher concentrations" accelerate it, though excessive levels can cause unwanted aggregation.

Challenges on the Horizon

Despite promising developments, myconanotechnology faces substantial hurdles. The "strain-dependent nature of nanomaterial synthesis" creates significant reproducibility challenges. Silver nanoparticles from Fusarium oxysporum, for instance, have been reported with sizes ranging from 5-15 nm to 20-50 nm in different studies.

Time and cost considerations present additional challenges. Fungi require "several days or weeks to grow, assimilate metal ions, and synthesise nanoparticles," making the process slower than conventional methods. Contamination risks can compromise entire batches, whilst operational costs increase due to sterile conditions requirements.

The Toxicity Question

The safety profile of mycogenic nanomaterials remains incompletely understood. Nanoparticles can enter the human body through "absorption into the skin, ingestion via the mouth, and inhalation via the nasal cavity," potentially causing cellular damage through reactive oxygen species generation.

However, research suggests that biogenic nanoparticles may prove safer than chemically synthesised counterparts. Studies indicate that "bio- and mycogenic nanoparticles" demonstrate reduced toxicity, though Mathur and Pillai note that "limited reports are present showing the toxicity of biosynthesised nanoparticles."

Environmental implications require careful consideration. Released nanoparticles can "accumulate in the soil and affect the soil characteristics of native inhabitants" and potentially interfere with beneficial microorganisms.

The Path Forward

The research highlights "the need for a regulatory framework for the environmental release and upscaling potential of mycogenic nanomaterials." This regulatory vacuum creates uncertainty for commercial development.

Despite challenges, myconanotechnology represents a significant advancement in sustainable manufacturing. Realising this potential requires addressing critical needs: standardising synthesis protocols, expanding toxicological studies, and developing "safe-by-design methods" for industrial-scale production.

Commercial viability depends on "optimisation of mycosynthesis methods on an industrial scale, considering the economic and environmental implications." As regulatory frameworks evolve and production methods mature, these biological manufacturers may indeed transform how we create nanoscale materials. The question is not whether fungi can produce nanomaterials—they demonstrably can—but whether we can harness this capability responsibly and at scale.