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Monascus purpureus was grown in submerged liquid culture using ammonium sulfate, sodium nitrate, and peptone as nitrogen sources while initial medium pH was adjusted to 2.5, 5.5, 6.5, or 8.0. The combined effect of culture pH and nitrogen source on the biosynthesis of yellow (ankaflavin and monascin) and orange (rubropunctatin and monascorubrin) pigments, plus the mycotoxin citrinin, was evaluated chromatographically. Optimum cultivation conditions, that is, initial pH 2.5 and 8.8 g/L peptone as a nitrogen source, resulted in high levels of production of yellow and orange pigments (sum of pigment concentration 1,138 mg/L) and negligible citrinin concentration (2 mg/L). [ABSTRACT FROM AUTHOR]

ABSTRACT BACKGROUND Millions of tons of feather waste from the poultry industry are disposed of annually despite containing a high level of keratin. The aim of this study was to compare the hydrolysis of non-treated feather waste using three different approaches (whole cell microbial digestion, enzymatic and chemical cleavage) and to test the use of hydrolysates as peptone substitutes in a culture medium. RESULTS Among bacterial isolates, Pseudomonas sp. P5 exhibited the highest keratinolytic activity and efficiency to hydrolyse raw feather material. The hydrolysates contained up to 301 mg L−1 of free amino acids and 6.2 g L−1 of peptides. Hydrolysates obtained by digestion using semi-purified keratinase from Pseudomonas sp. P5 were richer in amino acids (1191 mg L−1, 56% essential ones) but peptides were present in lower amounts (up to 3.3 g L−1). The third approach was feather treatment under mild alkaline conditions. This provided the highest amount of peptides (17.2 g L−1) but a significantly lower level of amino acids, especially the essential ones. CONCLUSIONS All approaches tested could convert raw feather waste into products of commercial value with proven use in a cultivation medium. The level of peptides, their molecular size and amino acid composition was dependent on the method used. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]