Production of Aspergillus niger biomass from aqueous extract of brewer's spent grain

Abstract

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 28^oC for eight days. A. niger cell biomass was harvested daily, pasteurized, centrifuged and dried (80^oC). Glucose supplemented medium gave the highest biomass (1.64g dry wt. /L) and protein content (0.86g/L) at the 4^th 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.