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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]

Abstract: The effect of different inducers on the cellulase and hemicellulase bioproduction by Aspergillus niger NRRL-567 using apple pomace as a substrate was investigated. Rapid production of different cellulase enzymes namely, FPase (filter paper cellulase), CMCase (carboxymethyl cellulase), BGL (β-glucosidase), and xylanase were observed with peak activity reaching between 48 and 72h of fermentation period. The higher FPase and BGL activities of 133.68±5.44IU/gram dry substrate (gds) and 60.09±3.43IU/gds, respectively were observed while using CuSO4 and veratryl alcohol after 48h of incubation time. The higher CMCase activity of 172.31±14.21IU/gds was obtained with lactose after 48h of incubation period. Similarly, higher xylanase activity of 1412.58±27.9IU/gds was observed with veratryl alcohol after 72h of fermentation time. This study sheds light on the rapid bioproduction of fungal cellulase and hemicellulase using low cost waste, apple pomace as substrate when supplemented with different inducers. [Copyright &y& Elsevier]