Chemiluminescent and fluorescent properties of extracellular red pigment from Talaromyces purpureogenus

Talaromyces purpureogenus is an attractive option for natural pigment production owing to its ability to produce large amounts of water-soluble extracellular red pigments. Recently, natural pigments have been used to develop halochromic biosensing applications, in which the colour change acts as a signal in response to a stimulus; however, the shelf-life and signal generation ability of packaging employing natural pigments maybe suboptimal because of potential reactions with environmental factors. Therefore, this study aimed to develop an alternative method for producing measurable signals from pigments. For this, the chemiluminescent and fluorescent properties of the pigments were explored. The pigment exhibited luminescence when exposed to hydrogen peroxide, which was affected by the reactant concentration, pH levels, and incubation time. Moreover, a rapid signal enhancement exceeding eight-fold was developed by adding luminol. The fluorescence spectrum was strongly affected by pH, with alkaline pH markedly increasing the fluorescence. Fluorescence was also found to be dependent on incubation time, with the maximum signal obtained at pH 12 and 72 h (∼16-fold increase over 0 h), and a model for the increase in fluorescence with time was developed (0.90 < R² < 0.99). The identification of pigment components confirmed the presence of atrorosin R, which had an isochromene/isoquinoline ring, and elucidated the planar structure of this pigment. These findings may aid in developing novel biosensors utilising fungal azaphilone pigments.