TABLE 1.
Influence of the carbohydrate source on cell growth and EPS production during S. thermophilus LY03 fermentationsa
| Carbohydrate source(s) | μmax (h−1) (r2) | rmax (h−1) (r2) | Biomassmax (g of CDM · liter−1) (h) | (HMM-EPS)max
|
(LMM-EPS)max
|
(Total EPS)max
|
||||
|---|---|---|---|---|---|---|---|---|---|---|
| mg of PDM · liter−1 (h) | Gal-Glu | mg of PDM · liter−1 (h) | Gal-Glu | mg of PDM · liter−1 (h) | Gal-Glu HMM | Gal-Glu LMM | ||||
| 0.22 M lactose | 1.1 (0.997) | 0.3 (0.999) | 4.5 (10.00) | 821 (8.50) | 4.14:1.00 | 766 (10.00) | 4.19:1.00 | 1,142 (10.00) | 3.91:1.00 | 4.02:1.00 |
| 0.15 M lactose + 0.14 M fructose | 0.9 (0.982) | 0.5 (0.986) | 4.3 (10.75) | 754 (10.00) | 4.09:1.00 | 348 (26.50) | 4.07:1.00 | 787 (10.00) | 3.82:1.00 | 3.94:1.00 |
| 1.0 (0.942) | ||||||||||
| 0.15 M lactose + 0.14 M galactose | 1.0 (0.994) | 0.3 (0.998) | 4.6 (7.50) | 537 (6.50) | 3.83:1.00 | 335 (25.00) | 3.78:1.00 | 615 (6.50) | 3.87:1.00 | 4.02:1.00 |
| 0.22 M lactose + 0.14 M fructose | 1.0 (0.996) | 0.1 (0.997) | 4.2 (15.25) | 674 (12.25) | 3.78:1.00 | 360 (15.25) | 4.19:1.00 | 884 (12.25) | 4.18:1.00 | 4.17:1.00 |
| 0.2 (0.944) | ||||||||||
| 0.15 M lactose + 0.14 M glucose | 1.1 (0.997) | 0.1 (0.997) | 4.3 (9.75) | 1,234 (10.75) | 3.89:1.00 | 480 (9.00) | 4.97:1.00 | 1,436 (10.75) | 3.89:1.00 | 3.97:1.00 |
| 1.0 (0.998) | ||||||||||
| 0.42 M glucose | 1.3 (0.991) | 0.3 (0.999) | 4.7 (12.00) | 340 (9.50) | 4.12:1.00 | 454 (22.00) | 4.03:1.00 | 504 (10.75) | 4.06:1.00 | 4.12:1.00 |
| 0.28 M glucose + 0.14 M fructose | 1.0 (0.999) | 0.3 (0.996) | 5.8 (16.25) | 671 (12.50) | 3.78:1.00 | 550 (26.00) | 3.69:1.00 | 776 (15.00) | 4.02:1.00 | 4.08:1.00 |
| 0.2 (0.999) | ||||||||||
| 0.28 M glucose + 0.14 M galactose | 0.8 (0.980) | 0.5 (0.971) | 5.4 (12.00) | 669 (12.00) | 3.74:1.00 | 462 (26.00) | 4.02:1.00 | 797 (10.75) | 4.00:1.00 | 4.00:1.00 |
| 0.7 (0.995)b | 0.5 (0.970)b | 5.1 (12.50)b | 603 (12.50)b | 3.90:1.00b | 433 (25.00)b | 4.12:1.00b | 625 (12.50)b | 4.13:1.00b | 4.07:1.00b | |
| 0.28 M glucose + 0.07 M lactose | 1.0 (0.997) | 0.3 (0.992) | 4.0 (8.00) | 731 (7.00) | 3.68:1.00 | 433 (25.00) | 3.88:1.00 | 934 (7.00) | 4.03:1.00 | 3.98:1.00 |
| 0.3 (0.960) | ||||||||||
a
Fermentations were performed with MRS broth at 42°C and at a controlled pH of 6.2. The biokinetic parameters μmax and rmax were estimated through modelling of the experimental data (the correlation coefficient r2 is given in parentheses beside these data).
b
Where two fermentations were carried out, two values are reported. The maximum amount of the biomass and the amounts of HMM-EPS, LMM-EPS, and total EPS produced are given. The harvesting times corresponding to the maximum values are given in parentheses. The composition of the EPS material is represented as the ratio of galactose to glucose.