Optimization of L-lactic acid production by fermentation of Huaimi dregs

Figures & data

Table 1. Uniform experimental design.

Run	Inoculum size x1 (%)	Fermentation time x2 (h)	Substrate ratio x3
1	6	36	3
2	6	60	3
3	10	48	3
4	14	48	3
5	4	60	4
6	8	60	4
7	10	24	4
8	14	24	4
9	4	36	5
10	8	36	5
11	12	24	5
12	12	48	5

Table 2. Orthogonal experimental design.

Run	Inoculum size x1 (%)	Fermentation time x2 (h)	Substrate ratio x3
1	4	36	4
2	4	36	5
3	4	40	4
4	4	40	5
5	5	36	4
6	5	36	5
7	5	40	4
8	5	40	5

Table 3. Effect of temperature on lactic acid yield.

Temperature (°C)	Lactic acid yield (mg/g)
26	0.1412
27	0.1505
28	0.1674
29	0.1442
30	0.1387

Table 4. Results from the uniform experimental design.

Run	Inoculum size x1 (%)	Fermentation time x2 (h)	Substrate ratio x3	Lactic acid yield y (mg/g)
1	6	36	3	0.2049
2	6	60	3	0.1534
3	10	48	3	0.1878
4	14	48	3	0.0349
5	4	60	4	0.2054
6	8	60	4	0.1501
7	10	24	4	0.2018
8	14	24	4	0.0909
9	4	36	5	0.2413
10	8	36	5	0.2478
11	12	24	5	0.1365
12	12	48	5	0.0878

Table 5. Results from the orthogonal experimental design.

Run	Inoculum size x1 (%)	Fermentation time x2 (h)	Substrate ratio x3	Lactic acid yield y (mg/g)
1	4	36	4	0.2552
2	4	36	5	0.2409
3	4	40	4	0.2589
4	4	40	5	0.2581
5	5	36	4	0.2597
6	5	36	5	0.2563
7	5	40	4	0.2598
8	5	40	5	0.2563
K1	1.0131	1.0121	1.0336
K2	1.0321	1.0331	1.0116
R	0.0190	0.0210	0.0220

Note: K1 is the average of 1 level in the certain factor;

K2 is the average of 2 level in the certain factor;

R is extreme value which is the largest K minus the smallest K.

Figure 1. Response surface plot of the lactic acid concentration with respect to inoculum size and fermentation time using the substrate ratio as a centre point.

Figure 2. Response surface plot of the lactic acid concentration with respect to inoculum size and substrate ratio using the fermentation time as a centre point.

Figure 3. Response surface plot of the lactic acid concentration with respect to fermentation time and substrate ratio using the inoculum size as a centre point.

Figure 4. Change of lactic acid amount with respect to inoculum size.

Figure 5. Change of lactic acid amount with respect to fermentation time.

Figure 6. Change of lactic acid amount with respect to substrate ratio.