Preliminary Examination of the Toxicity of Spalting Fungal Pigments: A Comparison between Extraction Methods

Abstract

Spalting fungal pigments have shown potential in technologies ranging from green energy generation to natural colorants. However, their unknown toxicity has been a barrier to industrial adoption. In order to gain an understanding of the safety of the pigments, zebrafish embryos were exposed to multiple forms of liquid media and solvent-extracted pigments with concentrations of purified pigment ranging from 0 to 50 mM from Chlorociboria aeruginosa, Chlorociboria aeruginascens, and Scytalidium cuboideum. Purified xylindein from Chlorociboria sp. did not show toxicity at any tested concentration, while the red pigment dramada from S. cuboideum was only associated with significant toxicity above 23.2 uM. However, liquid cultures and pigment extracted into dichloromethane (DCM) showed toxicity, suggesting the co-production of bioactive secondary metabolites. Future research on purification and the bioavailability of the red dramada pigment will be important to identify appropriate use; however, purified forms of the blue-green pigment xylindein are likely safe for use across industries. This opens the door to the adoption of green technologies based on these pigments, with potential to replace synthetic colorants and less stable natural pigments.

Chemical characterization and toxicity evaluation of fungal pigments for potential application in food, phamarceutical and agricultural industries

“…The lethality of the pigments was expected with consideration that most of the fungal metabolites produced in literature are reported to either display cytotoxicity or genotoxicity ( Poorniammal et al, 2021 ). A similar study using zebrafish embryos by Almurshidi et al (2021) evaluated the toxicity of red pigment (dramada) produced by spalting fungi ( Scytalidium cuboideumi ) and was only associated with significant toxicity above a concentration of 23.2 µM (approximately 0.0058 mg/mL). In addition, other pigments produced by Chlorociboria aeruginosa and Chlorociboria aeruginascens were also tested, it is interesting that the purified forms of pigments produced by these isolates did not exhibit any lethal endpoints at concentrations range 0–50 mM.…”

Preliminary Exploration of the Red Pigment from Scytalidium cuboideum as a Cellulosic Pulp Colorant

“…An additional advantage of using spalting-derived pigments is that, generally, they possess low toxicity compared to inorganic pigment colorants [40]. Pulp and paper manufacturers are constantly pushing for more environmentally friendly processes as they were considered a high-pollution industry in the past [38], and the adoption of fungal pigments can be aligned with trends like biopulping [38,41,42].…”

Safety Evaluation of Fungal Pigments for Food Applications

“…However, significant mortality was associated with impure fungal metabolites containing pigments. Hence, xylindein is considered as an environmentally safe pigmentation for future applications [55,90].…”