# Innovative mycosynthesis of chitosan nanoparticles via bionanofactory Penicillium crustosum: optimization, characterization, and application against building-deteriorating fungus, Trichosporon asahii

## TL;DR

This paper explores using chitosan nanoparticles made by a fungus to fight building-deteriorating fungi, offering an eco-friendly solution to biocorrosion.

## Contribution

The study introduces a novel eco-friendly method for synthesizing chitosan nanoparticles using Penicillium crustosum for anti-fungal applications.

## Key findings

- Chitosan nanoparticles (CNPs) were successfully biosynthesized with an average size of 26.19 nm.
- Higher concentrations of CNPs (250 and 500 µg/mL) showed significant fungicidal activity against Trichosporon asahii.
- CNPs caused structural damage to fungal spores and biofilm disruption, indicating potential for bio-safe coatings.

## Abstract

Biocorrosion of building materials is a global challenge that threatens both modern buildings and cultural heritage. This degradation is largely driven by interactions between microbes, particularly fungi, and various gaseous effluents containing nitrogenous, sulfurous, and carbonaceous aerosols from anthropogenic activities, leading to progressive biocorrosion of construction surfaces. Therefore, this study aims to reduce such detrimental effects using chitosan nanoparticles (CNPs). An eco-friendly biosynthesis approach was employed, using the cell-free supernatant of Penicillium sp. strain HNSAM-7 to produce the CNPs. This strain has been identified as Penicillium crustosum strain HNSAM-7 according to the analysis of ITS region sequence, together with its morphological characteristics. The physicochemical properties of CNPs were characterized; SEM and TEM analyses revealed that the biosynthesized CNPs resemble spheres, have a smooth surface, and varied in size, with an average size of 26.19 nm. The X-ray diffraction demonstrates the crystalline nature of CNPs. The FTIR analysis detected multiple functional groups involving O–H, -NH2, CH, CH2, CONH2, C–O, C–OH, C–O–C, –C≡CH, O = S = O, NH, C − O groups. CNPs have a surface with a positive charge, with a Zeta potential value of + 26.2 mV. Consequently, FCCCD was used to maximize CNPs’ production, achieving a maximum yield of 10.71 mg/mL under conditions of 1.19% (w/v) chitosan concentration, initial pH 4.99, and 99.94% (v/v) cell-free supernatant. The fungicidal activity of CNPs was evaluated in vitro against Trichosporon asahii using a killing-time assay. Higher concentrations of CNPs (250 and 500 µg/mL) demonstrated significant fungicidal activity. SEM analysis revealed substantial spore and mycelium structural damage, including disruption of biofilm architecture. These findings suggest that eco-friendly, biosynthesized CNPs have potential as possible bio-safe coatings for the protection of building structures against microbial corrosion.

The online version contains supplementary material available at 10.1186/s13068-025-02734-2.