Fed-batch culture of Sacchoromyces cerevisiae in sugar-cane blackstrap molasses: invertase activity of intact cells in ethanol fermentation

• Published in: Biomass & bioenergy 2000-07, Vol.19 (1), p.39-50
• Main Authors: Echegaray, O.F, Carvalho, J.C.M, Fernandes, A.N.R, Sato, S, Aquarone, E, Vitolo, M
• Format: Article
• Language: English
• Subjects: Ethanol; Fed-batch; Invertase; Molasses; Yeast
• ISSN: 0961-9534; 1873-2909
• DOI: 10.1016/S0961-9534(00)00022-2

Fed-batch cultures of Sacchoromyces cerevisiae were carried out in a 14 l fermenter (NBS, Microferm), containing sugar-cane blackstrap molasses supplemented with urea (0.5 g l −1) and penicillin V (500 ui/l), under the following conditions: 32(±1)°C; pH 4.5–5.0; N=200 min −1; inoculum and mash volume equal to 3.0 l and 7.0 l, respectively. The parameters varied were: filling time ( T: 1, 2 or 3 h), time constant ( K: 0, 0.8 or 1.6 h −1), total reducing sugar concentration in the feeding mash ( S m ) (170, 220 or 270 g l −1) and total amount of wet-pressed yeast in the inoculum ( M X0 ′) (800, 1300 or 1800 g). By applying the quadratic regression analysis the following equations were established: Y=78.2+2.5 X 3+2.5( X 3) 2−3.3 X 4−0.89 X 1, X 2−0.79 X 3, X 4 and P v =71.3+6.5 X 4−4.9 X 2, X 4 for the ethanol yield ( Y) and residual invertase activity ( P v ), respectively. The optimised ethanol and invertase formation was observed for high S m values under low M X0 ′- and high K.