Table 1.

Maximum acid produced by the organism under different conditions.

Acid produced	Pure culture (mM)	1% pulp density
		1-step bioleaching (mM)	2-step bioleaching (mM)
Citrate	51.6	38.6	33
Gluconate	16	171.16	163.7
Oxalate	4.62	1.93	1.27

Aspergillus niger produces citrate in the absence of fly ash, and gluconate in its presence.