Relationship between Molarity and Color in the Crystal (‘Dramada’) Produced by Scytalidium cuboideum, in Two Solvents

Abstract

Pigments from wood-decay fungi (specifically spalting fungi) have a long history of use in wood art, and have become relevant in modern science due to their longevity and colorfastness. They are presently under investigation as colorants for wood, bamboo, oils, paints and textiles. Major hurdles to their commercialization have been color repeatability (in that the same strain of the same species of fungus may produce different colors over time), and the binding of the pigments to glass storage containers. This is persistent as they do not naturally exist in a loose form. Due to these issues, the ‘standard’ color for each was historically determined not by the amount of pigment, but by the color in a solution of dichloromethane (DCM), using the CIE L*a*b colorspace. This method of standardization severely limited the use of these pigments in industrial applications, as without a dry form, standard methodologies for repeatable color processing into other materials could not be easily implemented. Recent studies have developed a method to crystalize the red pigment from Scytalidium cuboideum (Sacc. & Ellis) Sigler & Kang, producing a highly pure (99%) solid crystal named ‘Dramada’. Herein a method is detailed to compare the molarity of this crystallized pigment to variations in the color, to determine a color saturation curve (by weight) for the pigment from S. cuboideum in DCM and acetone. The molarities for this experiment ranged from 0.024 mM to 19 mM. Each molarity was color read and assigned a CIEL*a*b* value. The results showed that there was a correlation between the molarity and color difference, with the maximum red color occurring between 0.73 mM and 7.3 mM in DCM and between 0.97 mM to 0.73 mM in acetone. Extremely low molarities of pigment produced strong coloration in the solvent, and changes in molarity significantly affected the color of the solution. Having a saturation and color curve for the crystal ‘Dramada’ from S. cuboideum will allow for the reliable production of distinct colors from a known quantity (by weight) of pigment, erasing the final hurdle towards commercial development of the crystallized pigment from S. cuboideum as an industrial dyestuff.

Feasibility and Surface Evaluation of the Pigment from Scytalidium cuboideum for Inkjet Printing on Textiles

“…Both treatments showed the formation of well-defined rectangular crystalline structures, as well as a coloration that tended to red hues. This morphology has been previously observed on the crystallized form of the pure pigment [24,36], and differs of what has been previously observed in DCM [42], where the crystals showed a flattened structure that 'wrapped' around the polyester fiber. It is possible that effects like evaporation rate and solvent density play an important role in the formation of the crystalline structures, as well as interactions with the fabric surface.…”

“…Once extracted, the pigment was standardized to previously obtained CIELab values (L* = 82.32, a* = 26.84, b* = 13.19) by Robinson et al [41]. The CIELab values correspond to a 0.73 mM concentration of pure 'Dramada', based on the relationship between molarity and color described by Vega Gutierrez et al [36].…”

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

“…The crystals were then air-dried and placed in a glass vial. This method has been shown to result in crystals of high purity [ 15 , 55 ], with samples tested for purity in previous work [ 55 ].…”

“…Standards corresponding to the extracts with DCM have been previously used to determine pigment concentration based on CIE L*a*b* values, not dry weight, when working with pigmenting spalting fungi [ 17 , 53 , 55 , 58 ]. The color values were used instead of the dry weight due to the simplicity of a direct extraction from the dry plates with DCM.…”

Effective Molecular Identification of Ectomycorrhizal Fungi: Revisiting DNA Isolation Methods

“…While the color hue and value may potentially result from the presence of distinct pigments that could interfere with DNA isolation and downstream reactions [16], e.g., specific subtypes of melanin [9] or thelephoric acid [26], they might not necessarily showcase the amount of the pigments present in the sample. However, changes in the color saturation within the same hue angle are often caused by a different concentration of pigments producing such hue; as such, it is sometimes possible to use it to approximate the pigment concentration in an analyzed material [27]. The mycorrhizae mass did not seem to impact the final isolation results.…”