Bioproduction and extraction optimization of citric acid from Aspergillus niger by rotating drum type solid-state bioreactor

Abstract: Solid-state citric acid fermentation was conducted in a 12-L rotating drum type bioreactor. The effect of inducers, ethanol and methanol were studied on citric acid bioproduction by Aspergillus niger NRRL 567 cultivated on apple pomace as a solid-substrate. Optimum conditions achieved for higher citric acid bioproduction (220.6±13.9g/kg dry solids, DS) were 3% (v/v) methanol, intermittent agitation of 1h after every 12h at 2rpm and 1vvm of aeration rate and 120h incubation time. The response surface optimization proved effective for higher citric acid extraction from fermented solid-substrate. Higher citric acid extraction of 294.19g/kg DS was achieved at optimum conditions: extraction time of 20min, agitation rate of 200rpm and extractant volume of 15ml by response surface methodology. [Copyright &y& Elsevier]