Table 3. Effects of nitrogen source on malic acid production under the hydrolysate of corn cob 110 g/L as the carbon source in shake flasks.

Nitrogen source	Residual sugar (g/L)	Cell biomass (g/L)	Malic acid(g/L)	Productivity(g/L h)	Yield(g/g)
NH4NO3	12.38	24.82±0.52	30.01±2.52	0.25±0.021	0.31
NaNO3	10.56	25.36±0.96	27.50±2.08	0.23±0.017	0.28
(NH4)2SO4	9.98	25.48±1.22	36.24±0.65	0.30±0.005	0.36
NH4H2PO4	11.58	27.03±2.28	24.55±0.29	0.20±0.001	0.25
Yeast extract	13.20	26.44±0.98	23.83±2.61	0.19±0.016	0.25
Peptone	12.76	26.84±1.46	22.24±1.47	0.17±0.023	0.23
Control	11.12	28.12±3.02	18.41±0.29	0.15±0.002	0.19