Studies on red-pigment production by Talaromyces atroroseus TRP-NRC mutant II from wheat bran via solid-state fermentation

Abstract

Background Recently, the need of finding eco-friendly and less-hazardous pigments focused on an important alternative to harmful synthetic dyes. High productivity of various pigments from microorganisms, their rapid growth throughout the year, stability, and solubility of their pigments provide them advantages more than pigments produced from other natural sources.Objective The objective of this study is to improve red-pigment production from local isolated fungus Talaromyces atroroseus TRP-NRC on an inexpensive substrate (wheat bran) under solid-state fermentation system by using different mutants. Then, comparing between pigment released from fungi after mutation by different mutants, comparing the efficiency of different solvents for the extraction of red biopigments under different conditions, and then extraction of pigment and studying its structure.Materials and methods A novel locally non-mycotoxin-producing fungus T. atroroseus TRP-NRC was treated with γ-ray radiation followed by subjecting to ultraviolet rays and grown on wheat bran as a complete medium via solid-state fermentation technique. Different solvents, including water, ethanol, methanol, and acetone, were applied to extract pigment from dried fermented wheat bran. The effect of pH, temperature, and contact time on yield of pigment extraction was studied. Stability of extracted pigment to heat, autoclaving, and ultraviolet rays was studied. Antimicrobial activity of extracted pigment was studied. The extracted sample was subjected to high-performance liquid-chromatography analysis and gas chromatography–mass spectrometry analysis. Statistical analyses were performed using SPSS program at P value less than 0.05.Results and conclusion The mutant fungus (I) by gamma radiation achieved 30% increase in red pigment compared with the wild type. The mutant fungus (I) was subjected to ultraviolet rays, mutant (II) added 22% increase in pigment production compared with mutant obtained by gamma radiation. About 70% v/v of methanol, ethanol, and acetone were more efficient for extracting pigment with an advantage of 70% v/v acetone. The yield of pigment extraction was affected by pH, temperature, and contact time, and was at pH 6.5 at 50°C after 16 h. The produced pigment appeared to be heat-stable when subjected to heat from 30 to 80°C for 6 h. The pigment was also stable when autoclaved at 121°C for 15 min. The pigment was stable when subjected to ultraviolet rays for 6 h. The extracted pigment showed antibacterial activity against Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative). Gas chromatography–mass spectrometry analysis revealed that eighteen compounds were identified in the acetone extract of pigment. In general, the prevailing two compounds of fermented wheat bran by T. atroroseus TRP-NRC mutant-II extract were 9, octadenoic acid (43.72) and 1,1′-bicyclopropyl-2-octanoic acid, 2′-hexyl-, methyl ester 43.72%.