Production of Aspergillus niger biomass from aqueous extract of brewer's spent grain
Suitability of brewer`s spent grain (BSG) liquor for Aspergillus niger biomass (single cell protein) production was investigated. Aspergillus niger was grown in unsupplemented and supplemented (glucose or nitrogen sources [(NH4)2SO4, NaNO3, NH4Cl, NH4NO3 and KNO3]) BSG liquor by submerge fermentation on rotary shaker (120 rpm) at 28oC for eight days. A. niger cell biomass was harvested daily, pasteurized, centrifuged and dried (80oC). Glucose supplemented medium gave the highest biomass (1.64g dry wt. /L) and protein content (0.86g/L) at the 4th day of fermentation. (NH4)2SO4 was the best N2 supplement with a biomass yield of 1.43g dry wt. /L and protein content of 0.81 g /L. This study demonstrated that the production of Aspergillus niger biomass is a way of utilizing BSG (a low cost readily available by-product of brewing) to ensure a sustainable reuse of its bioresources. It also established that Aspergillus niger biomass production can be enhanced by supplementation of BSG liquor with glucose or (NH4)2SO4 with a maximum fermentation period of four days.
Keywords: Biomass, Brewer`s spent grain, Aspergillus niger, Protein, Fermentation.