Optimization of four parameters,
i.e., zinc (Zn
2+), magnesium (Mg
2+), manganese (Mn
2+) and yeast extract for bioethanol production from sweet sorghum juice by
Saccharomyces cerevisiae NP 01 under very high gravity (VHG, 270 g·L
−1 of total
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Optimization of four parameters,
i.e., zinc (Zn
2+), magnesium (Mg
2+), manganese (Mn
2+) and yeast extract for bioethanol production from sweet sorghum juice by
Saccharomyces cerevisiae NP 01 under very high gravity (VHG, 270 g·L
−1 of total sugar) conditions was performed using an L
9 (3
4) orthogonal array design. The fermentation was carried out at 30 °C in 500-mL air-locked Erlenmeyer flasks at the agitation rate of 100 rpm and the initial yeast cell concentration in the juice was approximately 5 × 10
7 cells·mL
−1. The results showed that the order of influence was yeast extract > Mn
2+ > Zn
2+ > Mg
2+ and the optimum nutrient concentrations for the ethanol fermentation were Zn
2+, 0.01; Mg
2+, 0.05; Mn
2+, 0.04; and yeast extract, 9 g·L
−1. The verification experiments under the optimum condition clearly indicated that the metals and nitrogen supplementation improved ethanol production efficiency under the VHG fermentation conditions. The ethanol concentration (
P), yield (
Yp/s) and productivity (
Qp) were 120.58 ± 0.26 g·L
−1, 0.49 ± 0.01 and 2.51 ± 0.01 g·L
−1·h
−1, respectively, while in the control treatment (without nutrient supplement)
P,
Yp/s and
Qp were only 93.45 ± 0.45 g·L
−1, 0.49 ± 0.00 and 1.30 ± 0.01 g·L
−1·h
−1, respectively.
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