TABLE 2.
Comparison of process modes for l-malic acid production with A. oryzae DSM 1863 in 100-ml shake flasks.
| Process mode a | Time b (h) | CaCO3 addition c (g) | MA productivity d (g) | SD (g) | Glucose consumption rate d (g) | SD (g) | Yield (g/g) | SD (g) | pH min (-) | SD (-) |
|---|---|---|---|---|---|---|---|---|---|---|
| Batch A | 144 | — | 3.88 | 0.70 | 5.74 | 0.17 | 0.68 | 0.13 | 6.36 e | 0.09 |
| RB A | 453 | 6 | 17.80 | 0.42 | 44.05 | 0.54 | 0.40 | 0.01 | 6.31 | 0.01 |
| RB B | 453 | 3 | 15.02 | 0.81 | 43.24 | 0.73 | 0.35 | 0.02 | 6.09 | 0.01 |
| FB C | 453 | — | 4.67 | 0.29 | 41.90 | 0.33 | 0.11 | 0.01 | 5.19 | 0.05 |
Best performing experiments for the individual process modes batch, repeated-batch (RB), and fed-batch (FB) were selected for comparison of the process modes based on specific process characteristics.
For Batch A, the cultivation time until the maximum product titer is given (total cultivation time 333 h). For RB A/B and FB C, the overall cultivation time is given.
Regular additions of calcium carbonate during cultivation. Starting concentration of calcium carbonate of all cultivations was 90 g/L and is not included.
Overall l-malic acid/glucose amount produced/consumed as sum of all repeated-batch or fed-batch cycles. For Batch A, the amount of l-malic acid/glucose produced/consumed until 144 h is given.
Average pH value minimum (after 263 h), disregarding the pH drop of Batch A3 at 191 h.