Optimizing Xylindein from Chlorociboria spp. for (Opto)electronic Applications

Abstract

Xylindein, a stable quinonic blue-green fungal pigment, has shown potential for use not only as a colorant but also as an (opto)electronic material. As no method presently exists to synthesize the pigment, organic production by slow-growing fungi from the genus Chlorociboria is the only method to obtain it. This has resulted in limited quantities of impure xylindein, hampering research. In order to improve quantity and quality of pigment for optoelectronic applications, speed of xylindein production by Chlorociboria aeruginosa and its relative purity were compared across liquid and solid-state fermentation conditions on selected nutrient sources. Liquid 2% malt shaking cultures produced the same amount of pigment in 5 weeks that previous testing produced in 2 months. Xylindein generation speed, purity, and conductive properties of produced pigment for (opto)electronics was then compared between two Chlorociboria species native to North America, Chlorociboria aeruginosa and Chlorociboria aeruginascens. Differences were seen in the conductivity of extracted pigment between species and strains, with xylindein from C. aeruginascens strain UAMH 7614 producing films with the highest effective electron mobility. The identification of the most effective growth conditions and the strain with highest purity xylindein production should support further development of sustainable organic (opto)electronics. Future work identifying new strains with reduced production of interfering metabolites and new extraction methodologies will help to produce very low cost xylindein, supporting sustainable technologies based on the pigment.

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

“…Notably, in live media testing at 120 hpf, C. aeruginosa showed only half the mortality of C. aeruginascens , and in sterilized media at 24 hpf it showed no toxicity while C. aeruginascens had 100% deformities. Variation in pigment production between the two species has been seen in other studies [ 70 , 71 ], including variation in the production of a yellow pigment in addition to differential production of xylindein [ 54 ].…”

“…The differences in toxicity seen between the liquid cultures and the solid cultures are likely explained by variation in differential metabolite production. Variation in growth conditions is known to alter the secondary metabolite production of fungi generally [ 67 , 68 , 69 ], and variation in metabolite production in spalting fungi specifically [ 70 ]. Increased co-production of bioactive compounds in the liquid cultures compared to that in the wood chip plates is likely, especially as pigmented metabolite production is often seen earlier in the lab in liquid compared to solid cultures.…”

Genetic and Environmental Factors Influencing the Production of Select Fungal Colorants: Challenges and Opportunities in Industrial Applications

“…As a blue-green quinonic colorant produced by Chlorociboria, xylindein's utilization in the field of (opto)electronics represents a novel and cutting-edge technology of fungal colorants. The excellent physical properties of xylindein, exhibiting a π-conjugated core structure and aggregate formation, enable electron transport with mobility of up to −0.4 cm 2 /(V•s) in amorphous xylindein films and potentially higher in high-purity xylindein [82][83][84]. Accordingly, xylindein is a potential candidate for sustainable organic electronics, thereby contributing to environmentally friendly technologies and the circular economy.…”

Ultrafast Triplet State Formation in a Methylated Fungi-Derived Pigment: Toward Rational Molecular Design for Sustainable Optoelectronics

“…For example, chromophores with accessible triplet states may increase the probability for charge separation and capture due to long excited-state lifetimes and carrier diffusion lengths. , In particular, triplet excitons can have diffusion lengths ranging from ∼30 to 300 nm, much longer than singlet excitons with typical diffusion lengths of ∼5–20 nm. ,, Some light-harvesting materials and organic light-emitting diodes (OLEDs) exploit these properties, though they often rely on heavy-metal complexes with more intense spin–orbit coupling (SOC) to enhance intersystem crossing (ISC). Achieving these properties with organic chromophores is desirable due to their availability and simple processing requirements that could be upscaled for mass production . In addition to the reduced cost compared to inorganic counterparts, environmental concerns from the processing and waste of metals (e.g., toxicity) is alleviated when working with organic chromophores.…”

“…Achieving these properties with organic chromophores is desirable due to their availability and simple processing requirements that could be upscaled for mass production. 13 In addition to the reduced cost compared to inorganic counterparts, environmental concerns from the processing and waste of metals (e.g., toxicity) is alleviated when working with organic chromophores. Many of these pigments contain nitrogen heterocyclic aromatics and carbonyl groups because the orbital mixing provided by the nonbonding (n) orbitals improves SOC.…”