Study of Saccharomyces uvarum CCMI 885 Physiology under Fed-Batch, Chemostat and Accelerostat Cultivation Techniques

Helena Albergaria, Luis C. Duarte, M. T. Amaral-Collaço and Francisco M. Gírio*

INETI, Departamento de Biotecnologia, Estrada do Paço do Lumiar, 22, 1649–038 Lisboa, Portugal 

Article history:
Received November 10, 1999
Accepted January 21, 2000

Key words:
yeast physiology, Saccharomyces uvarum, critical specific growth rate, accelerostat, fed-batch

Summary:
Physiological studies of the enological yeast strain Saccharomyces uvarum CCMI 885 (Saccharomyces cerevisiae var. uvarum) were carried out under different cultivation techniques, such as chemostat, fed-batch and the accelerostat (A-stat) procedure. Continuous cultivations were carried out on grape must medium, containing a mixture of hexoses (glucose/ fructose) and ethanol with a total carbon compounds concentration of 20.6 g/L in the feed. In order to carefully study the yeast behaviour in a wide range of growth rates, the dilution rate (D) in the accelerostat technique (A-stat) varied between an initial value of 0.14 h^–1 and a final value of 0.41 h^–1, with a constant acceleration rate of 0.011 h^–2. During this procedure, the shift from purely oxidative to respiro-fermentative metabolism was observed and the critical specific growth rate (
µ_crit) was found to be 0.21 h^–1. Chemostat steady- state cultures were studied at three different dilution rates: 0.10, 0.14 and 0.29 h^–1. The chemostat metabolic rates and the growth yields were similar to those obtained under A-stat cultivation. The maximum specific growth rate found for this strain by the wash-out method, 0.37 h^–1, was lower than that obtained by A-stat (0.41 h^–1). A fed-batch cultivation was performed on the same grape must medium with a feed rate leading to a specific growth rate of 0.19 h^–1, with a purely oxidative growth of the yeast culture. The A-stat procedure is, therefore, a powerful technique providing fast and reliable information about yeast physiology. 

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