Enhancing bioprocessing of red pigment from immobilized culture of gamma rays mutant of the endophytic fungus Monascus ruber SRZ112

Abstract

Considerable attention has been paid to exploring the biotechnological applications of several Monascus sp. for pigment production. In this study, our focus is on enhancing the bioprocessing of red pigment (RP) derived from the endophytic fungus Monascus ruber SRZ112. To achieve this, we developed a stable mutant strain with improved productivity through gamma irradiation. This mutant was then employed in the immobilization technique using various entrapment carriers. Subsequently, we optimized the culture medium for maximal RP production using the Response Surface Methodology. Finally, these immobilized cultures were successfully utilized for RP production using a semi-continuous mode of fermentation. After eight cycles of fermentation, the highest RP yield by immobilized mycelia reached 309.17 CV mL^-1, a significant increase compared to the original titer. Importantly, this study marks the first report on the successful production of Monascus RP in a semi-continuous mode using gamma rays' mutant strain, offering prospects for commercial production.

Keywords: Monascus ruber; Endophytic fungi; Gamma Radiation Mutagenesis; Immobilization; Red pigment; Response Surface Methodology.

Fig. 1

Dry biomass (g L⁻¹) and RP yield (CV mL.⁻¹) by Monascus ruber SRZ112 parent and the isolated mutants. Cultures were grown in 50 mL PD medium (pH 6.0) inoculated with 1 mL inoculum size of 7-day-old culture and incubated at 120 rpm and 25ºC for 10 days. The calculated mean is for triplicate measurements from two independent experiments. The means with * are significantly different from the control (LSD test, P ≤ 0.05)

Fig. 2

Colony phenotype and microscopic morphology of the parent strain M. ruber SRZ112 (A) and the developed mutant M. ruber SRZ112—m22 (B). Colony growth was observed on Czapek–Yeast autolysate agar after incubation for 10 days at 25 °C. The appearance of both strains was studied under the light microscope after staining with lactophenol cotton blue

Fig. 3

2D contour and 3D surface plots showing the effect of medium components on RP yield by immobilized spores of M. ruber SRZ112—m22 in alginate beads

Fig. 4

2D contour and 3D surface plots showing the effect of medium components on RP yield by immobilized mycelia of M. ruber SRZ112—m22 in alginate beads