Study of Saccharomyces uvarum CCMI 885 physiology under fed-batch, chemostat and accelerostat cultivation techniques

Physiological studies of the enological yeast strain Saccharomyces uvarum C CMI 885 (Saccharomyces cerevisiae var. uvarum) were carried out under diffe rent cultivation techniques, such as chemostat, fed-batch and the acceleros tat (A-stat) procedure. Continuous cultivations were carried out on grape m ust 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 ord er 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 con stant acceleration rate of 0.011 h(-2). During this procedure, the shift fr om purely oxidative to respiro-fermentative metabolism was observed and the critical specific growth rate (mu(crit)) was found to be 0.21 h(-1). Chemo stat 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 yie lds were similar to those obtained under A-stat cultivation. The maximum sp ecific 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 cultivat ion 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 th e yeast culture. The A-stat procedure is, therefore, a powerful technique p roviding fast and reliable information about yeast physiology.