The Joint Effect of pH Gradient and Glucose Feeding on the Growth Kinetics of Lactococcus lactis CECT 539 in Glucose-Limited Fed-Batch Cultures

Fig. 1.

Fig. 2.

Fig. 3.

Significant values (p < 0_05) for the constants in model [7] for the different dependent variables in the second fed-batch culture_

Parameter	Biomass	Viable cell counts	Nisin	Lactic acid	Acetic acid	Butane-2,3-diol
A1	0.46 ± 0.043	0.58 ± 0.053	0.42 ± 0.040	10.19 ± 0.405	0.41 ± 0.032	0.23 ± 0.062
A2	−3.32 ± 0.351	−1.75 ± 0.062	−27.69 ± 1.011	−8.10 ± 0.621	−2.19 ± 0.027	−3.15 ± 0.333
A3	0.58 ± 0.059	0.45 ± 0.011	6.53 ± 0.462	1.79 ± 0.109	0.44 ± 0.024	0.63 ± 0.097
A4	0.53 ± 0.038	0.26 ± 0.065	4.73 ± 0.516	−0.35 ± 0.017	0.42 ± 0.023	0.72 ± 0.065
A5	−0.04 ± 0.005	−0.01 ± 0.003	−0.10 ± 0.013	0.03 ± 0.006	−0.02 ± 0.001	−0.04 ± 0.004
A6	0.11 ± 0.006	NS	NS	NS	NS	NS
R2	0.9973	0.9906	0.9950	0.9959	0.9794	0.9856
RPDM (%)	0.987	0.326	3.775	2.609	3.988	3.602
VpHopt	1.82	1.96	2.12	2.26	2.47	2.49
pHopt = 7.0 – VpHopt	5.18	5.04	4.88	4.74	4.53	4.51
Gopt (g/l)	10.55	11.10	22.83	5.30	11.17	10.27

The optimal final culture pH values for different bacteriocins produced by lactic acid bacteria_

Bacteriocin	Producing strain	Optimum final pH	Culture medium	Reference
Mesenterocin 5	Leuconostoc mesenteroides UL5	4.24 to 4.34	Whey	Daba et al. 1993
Pediocin AcH	Pediococcus acidilactici LB42-923	3.70	TGE broth	Yang and Ray 1994
Nisin	Lactococcus lactis ATCC 11454	5.80	TGE broth	Yang and Ray 1994
Leuconocin Lcm1	Leuconostoc carnosum Lm1	5.00	TGE broth	Yang and Ray 1994
Sakacin A	Lactobacillus sake LB 706	4.50	TGE broth	Yang and Ray 1994
Nisin	Lactococcus lactis ATCC 7962	4.90	Whey permeate	Flôres and Alegre 2001
Carnocin KZ213	Carnobacterium piscicola 213	4.80 to 5.08	MRS broth	Khouiti and Simon 2004
Nisin	Lactococcus lactis ATCC 11454	4.60	MRS + milk	Penna et al. 2005
		4.80	M17 + milk
Nisin	Lactococcus lactis ATCC 11454	4.65 to 4.96	Whey + YE (5 g/l)	Jozala et al. 2011

Significant values (p < 0_05) for the constants in model [7] for the different dependent variables in the first fed-batch culture_

Parameter	Biomass	Viable cell counts	Nisin	Lactic acid	Acetic acid	Butane-2,3-diol
A1	4.12 ± 0.631	1.86 ± 0.084	1.13 ± 0.113	5.71 ± 0.235	1.16 ± 0.003	2.75 ± 0.277
A2	−3.60 ± 0.545	−1.56 ± 0.072	8.67 ± 0.4244	−4.04 ± 0.225	−0.70 ± 0.012	−2.00 ± 0.265
A3	0.83 ± 0.116	0.41 ± 0.015	−2.07 ± 0.206	0.88 ± 0.054	0.12 ± 0.005	0.37 ± 0.064
A4	−1.09 ± 0.383	−0.15 ± 0.051	−9.25 ± 1.547	−0.92 ± 0.040	−0.46 ± 0.021	−0.19 ± 0.021
A5	0.14 ± 0.062	0.03 ± 0.008	2.93 ± 0.314	0.26 ± 0.019	0.15 ± 0.011	0.03 ± 0.003
A6	0.35 ± 0.168	NS	0.74 ± 0.203	NS	NS	NS
R2	0.9950	0.9948	0.9993	0.9986	0.9949	0.9954
RPDM (%)	3.335	0.228	1.121	3.760	1.701	5.809
VpHopt	1.81	1.92	2.32	2.30	2.83	2.40
pHopt = 7.0 – VpHopt	5.19	5.08	4.68	4.70	4.17	4.60
Gopt (g/l)	1.64	2.72	1.29	1.76	1.41	2.80

Mean composition (g/l) of the substrates used as culture media_

Nutrient	DW medium	CMPW medium	CMPWGP medium
Lactose	22.62 ± 0.05	−	−
Glucose	−	101.72 ± 0.17	400.00 ± 0.01
Total nitrogen	0.433 ± 0.02	0.540 ± 0.01	0.431 ± 0.02
Total phosphorus	0.227 ± 0.02	0.060 ± 0.00	3.210 ± 0.06
Proteins	2.07 ± 0.01	3.47 ± 0.03	2.75 ± 0.02