Screening of Auricularia auricula strains for strong production ability of melanin pigments

Abstract

Melanin pigments have great application value and development potential in food industry to use as nature functional food colorants. In initial study, twenty-two Auricularia auricula strains were screened for stronger production ability of melanin pigments by solid culture. Three A. auricula strains (RF201, QD2 and QD6) with higher pigment production capacity were selected for further study through submerged culture supplementing 1 g/L l-tyrosine. The maximal pigment yields of A. auricula RF201, QD2 and QD6 were 493.9, 367.6 and 318.5 mg/L, respectively. Among three strains, A. auricula RF201 possessed the strongest production ability of melanin pigments. The present study indicated that A. auricula RF201 could be used as potential excellent producer of melanin pigments.

Studies on the biosynthetic pathways of melanin in Auricularia auricula

“…For solid culture, 8 mm diameter mycelium discs obtained from PDA Petri dishes were transferred to new PDA Petri dishes and incubated at 25℃. For submerged fermentation, 10 mycelium discs were picked from the edge of the activated A. auricula colony and were put into the liquid potato dextrose broth (PDB) medium and then incubated at 25℃ and 160 rpm for 3 days to obtain the seed liquid [26]. The inoculums (10%, v/v) were transferred into an triangular flask (250 ml) contained 50 ml of fermentation medium (improved and optimized according to Zou's method [21], MgSO 4 0.2%, KH 2 PO 4 0.1%, NaCl 0.1%, wheat bran juice 30%, casein 0.4%, tyrosine 0.2%, and vitamin B 1 0.01%, pH 7.0) at 25℃ and 160 rpm with.…”

“…Took 2 ml of fermentation broth, were centrifuged at 4000 rpm for 10 min, the supernatant were adjusted to pH 9.0 with 1 mol/L NaOH to completely dissolve melanin, then adjusted to pH 2.0 with 1 mol/L HCl, centrifuged at 12,000 rpm for 20 min to precipitate melanin. Washed with chloroform, ethyl acetate, absolute ethanol, and distilled water successively, dissolved with 1 mol/L NaOH solution, and the absorbance value was measured at 400 nm [17,22,26,27].…”