Orange processing waste valorisation for the production of bio-based pigments using the fungal strains Monascus purpureus and Penicillium purpurogenum

Orange processing wastes have been evaluated for the production of pigments by the fungal strains Monascus purpureus ATCC 16365 and Penicillium purpurogenum CBS 113139. Solid state fermentations were initially conducted on waste orange peels with the fungal strain M. purpureus aiming to assess various pigment extraction methods, the effect of particle size as well as the effect of nitrogen addition and incubation time. Under the optimum conditions, solid state fermentations were also performed with the strain P. purpuronegum to evaluate pigment production on waste orange peels. M. purpureus was more efficient than P. purpurogenum for the production of pigments during solid state fermentation, yielding 9 absorbance units (AU) per g of dry fermented substrate. Semi-solid state fermentations were subsequently conducted by suspending waste orange peels in liquid media leading to pigment production of up to 0.95 AU mL−1. Submerged fermentations were carried out with both fungal strains using aqueous extracts from either boiled or hydrodistilled orange peel residues as the sole fermentation medium showing that up to 0.58 AU mL−1 of pigment production could be achieved. Each fermentation feedstock and fermentation mode influenced significantly the production of pigments by each fungal strain used