Combinatorial strategies for production improvement of red pigments from Antarctic fungus Geomyces sp. 

Abstract

Natural red pigments have been widely used as food and cosmetics additives. However, due to toxic byproducts or allergen issues, it is still necessary to look for some other red pigment products. This study proposed combinatorial strategies to improve production of a new kind of red pigments from the fungus Geomyces WNF-15A, isolated from Antarctica. A high-production medium was developed by statistical experimental design, which was further simplified for industrial use by single-factor experiments. Strain breeding by atmospheric room temperature plasma mutagenesis generated a mutant, Geomyces sp. WNF-15A-M210, which increased production of red pigments by 24.4% and shortened culture phase by 33.3% comparing with the wild-type. The production of red pigments by this mutant favored a weak alkaline condition but required only mild dissolved oxygen tension. Control of initial pH 8.5 (process pH around 7.5) increased red pigments production by 19% comparing with natural condition. Precursor and inhibitor addition experiments indicated that the red pigments were synthesized by polyketide pathway, and feeding 6 mmol/L precursor of sodium acetate by three aliquots at days 3 to 5 improved biosynthesis of red pigments by 27%. Finally, the developed culture process was verified in a 5-L stirred tank bioreactor. The red pigments production of the pH regulation group reached 1.11-fold of the control and 1.95-fold of the precursor regulation group, respectively. This study provides high-production strain, optimized medium, and bioprocess for the possible industrial production of Antarctic Geomyces red pigments in future.

Transposon insertion mutation of Antarctic psychrotrophic fungus for red pigment production adaptive to normal temperature

“…Our previous studies have shown that atmospheric and room temperature plasma (ARTP) is highly lethal to Geomyces sp. WNF-15A, with a fatality rate of up to 90% (Huang et al, 2020 ). We obtained a dominant mutant M210 using ARTP.…”

“…For shake flask culture, the second-order seed was inoculated in 75 mL medium S by 6% (vol/vol), and 20 glass beads with a diameter of 4 mm were added. It was then cultured in dark at 130 r/min for 16 days (Huang et al, 2020 ). Three biological replicates were set for each experiment.…”

“…The production of red pigment was monitored by OD 520 using a UV-2102 PC spectrophotometer (UNICO [Shanghai] Instruments Co., Ltd, China). The measurement method of red pigment production was performed as described previously (Huang et al, 2020 ). The number of protoplasts and spores was determined using a cytometer (Shanghai Titan Technology Co., Ltd).…”

“…S2 ). Of note, Geomyces sp.WNF-15A produced high-level red pigment below 14°C, but the production decreased by 60%–70% at above 20°C and almost blocked at 25°C (Huang et al, 2020 ).…”

Minos and Restless transposon insertion mutagenesis of psychrotrophic fungus for red pigment synthesis adaptive to normal temperature

“…The seed medium and fermentation medium S for Geomyces sp. WNF-15A and its mutants were used as previously described (Huang et al, 2020).…”