Optimization of l-malic acid production from acetate with Aspergillus oryzae DSM 1863 using a pH-coupled feeding strategy

Table 2 Fermentation results for 2.5-L bioreactor cultivations with A. oryzae for l-malic acid production

Fermentation No.	Substrate metabolized [g]^a	Malic acid [g/L]	Y_{P/S, malic acid} [g/g]^b	Malic acid productivity [g/L/h]	Total acid [g/L]^c	Y_{P/S, total acid} [g/g]	Total acid productivity [g/L/h]	Sampling point for calculation [h]
I	50.12 ± 1.29	5.62 ± 0.30	0.16 ± 0.01	0.039 ± 0.002	11.99 ± 1.08	0.33 ± 0.04	0.083 ± 0.007	144
II	51.68 ± 0.74	6.29 ± 0.78	0.17 ± 0.02	0.044 ± 0.005	13.25 ± 1.47	0.35 ± 0.04	0.092 ± 0.010	144
III	104.47 ± 2.50	18.53 ± 0.90	0.26 ± 0.01	0.097 ± 0.005	35.82 ± 1.16	0.50 ± 0.00	0.187 ± 0.006	192
IV	96.62 ± 3.72	14.75 ± 1.20	0.23 ± 0.01	0.077 ± 0.006	28.90 ± 2.50	0.45 ± 0.01	0.151 ± 0.013	192
V	94.52 ± 2.78	16.22 ± 0.71	0.26 ± 0.00	0.084 ± 0.004	31.43 ± 1.02	0.50 ± 0.00	0.164 ± 0.005	192
VI	153.18 ± 6.12	29.53 ± 1.82	0.29 ± 0.01	0.112 ± 0.007	54.20 ± 3.23	0.53 ± 0.01	0.205 ± 0.012	264
VII	139.44 ± 6.60	18.66 ± 0.50	0.20 ± 0.01	0.071 ± 0.002	37.22 ± 2.49	0.40 ± 0.01	0.141 ± 0.009	264

Data represent means ± standard deviation, n = 2 (I–VI) or n = 3 (VII)
^aRefers to the sum of substrate metabolized from acetate and glucose. Initially, 45 g/L acetic acid and 5 g/L of glucose were present in the medium
^bY_{P/S, malic acid} [g/g] = substrate specific malic acid yield calculated as g(malic acid)/g(consumed substrates)
^cRefers to all organic acids produced during the cultivation (see Table 3)

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