Improvement on the productivity of continuous tequila fermentation by Saccharomyces cerevisiae of Agave tequilana juice with supplementation of yeast extract and aeration

AMB Express

Table 1 Concentration of compounds and calculated parameters on the steady state of aerated (at 0.02 vvm) or non-aerated S. cerevisiae continuous cultures, fed with sterilized (SM) or non-sterilized medium (NSM)

Compound (g L⁻¹)	Aeration and dilution rates (D)
	0 vvm and 0.08 h⁻¹		0.02 vvm and 0.08 h⁻¹
	SM	NSM	SM	NSM
A (Non-supplemented with yeast extract)
Biomass	5.90 ± 0.21	4.93 ± 0.42	7.33 ± 0.29	6.83 ± 0.72
Ethanol	38.25 ± 0.84	37.48 ± 1.61	41.87 ± 0.62	39.97 ± 0.04
R sugars	14.46 ± 0.52	26.52 ± 0.33	4.73 ± 0.57	12.18 ± 1.63
Fructose	4.27 ± 1.23	26.27 ± 3.35	9.56 ± 2.33	10.76 ± 1.16
Glucose	2.17 ± 0.37	0.90 ± 0.14	2.62 ± 0.10	0.39 ± 0.01
Succinic acid	0.16 ± 0.01	0.06 ± 0.08	0.21 ± 0.09	0.12 ± 0.00
Glycerol	4.48 ± 0.38	3.08 ± 0.23	7.00 ± 0.11	4.44 ± 0.14
Diacetyl	nd	nd	nd	nd
Acetic acid	nd	nd	nd	nd
Acetoin	0.33 ± 0.12	nd	nd	0.18 ± 0.03
NH₄ ⁺	1.80 ± 0.22	1.55 ± 0.17	1.17 ± 0.09	0.89 ± 0.05
Y_X/S	0.069 ± 0.002	0.067 ± 0.005	0.077 ± 0.003	0.078 ± 0.007
Y_P/S	0.447 ± 0.007	0.510 ± 0.020	0.439 ± 0.004	0.455 ± 0.008
P_P	3.060 ± 0.067	2.998 ± 0.129	3.350 ± 0.050	3.198 ± 0.003
pH	3.0 ± 0.1	2.9 ± 0.3	2.8 ± 0.1	2.7 ± 0.3

Compound (g L⁻¹)	Aeration and dilution rates (D)
	0 vvm and 0.10 h⁻¹		0.02 vvm and 0.12 h⁻¹
	SM	NSM	SM	NSM
B (Supplemented with yeast extract)^a
Biomass	6.57 ± 0.68	6.42 ± 0.23	8.16 ± 0.70	8.28 ± 0.90
Ethanol	42.95 ± 2.86	46.22 ± 3.20	45.11 ± 0.49	46.92 ± 1.87
R sugars	5.86 ± 0.48	6.60 ± 0.25	7.53 ± 0.89	7.23 ± 0.09
Fructose	3.56 ± 0.19	5.03 ± 0.32	2.91 ± 0.55	6.63 ± 0.04
Glucose	0.06 ± 0.04	0.41 ± 0.19	nd	0.57 ± 0.00
Succinic acid	0.08 ± 0.06	0.14 ± 0.02	0.08 ± 0.06	0.12 ± 0.04
Glycerol	2.76 ± 0.17	3.93 ± 0.17	3.00 ± 0.08	3.14 ± 0.06
Diacetyl	nd	nd	nd	nd
Acetic acid	nd	nd	nd	nd
Acetoin	nd	nd	nd	nd
NH₄ ⁺	1.16 ± 0.12	1.59 ± 0.51	0.94 ± 0.05	0.77 ± 0.13
Y_X/S	0.070 ± 0.007	0.069 ± 0.002	0.088 ± 0.007	0.089 ± 0.010
Y_P/S	0.456 ± 0.028	0.495 ± 0.033	0.488 ± 0.001	0.506 ± 0.020
P_P	4.295 ± 0.286	4.622 ± 0.320	5.413 ± 0.059	5.630 ± 0.224
pH	2.8 ± 0.3	2.7 ± 0.1	2.6 ± 0.2	2.6 ± 0.3

Medium contained agave juice (adjusted at 100 g L⁻¹ of R sugars), ammonium sulfate (1 g L⁻¹) and ammonium phosphate monobasic (4 g L⁻¹). Y_X/S is biomass yield (g g⁻¹). Y_P/S is ethanol yield (g g⁻¹). P_P is ethanol productivity [g (Lh)⁻¹]. Values are the means ± standard deviations (n = 3)
R sugars are Reducing sugars, nd compound not detected under the analysis conditions
^aExperiments using media supplemented with yeast extract were performed at higher D, because this supplementation allowed this increase without losing stability in the continuous culture