he indigenous strains, stored at −80 °C before use, were thawed. The S.c. 3′ strain was grown in liquid GPY medium (4% glucose, 0.5% peptone, 0.5% yeast extract) at 30 °C for 24 h. An aliquot of this culture was added at a concentration of 2% to 100 mL of liquid GPY medium and incubated for 16 h at 30 °C to obtain the inoculum used in the bioreactor. The H.u. 283 strain was grown on GPY agar and incubated at 30 °C for 48 h. Surface growth from one plate was transferred to 100 mL of liquid GPY medium and incubated for 72 h at 30 °C to obtain the inoculum used in the bioreactor.
To obtain enough biomass to be used in the fermentation of apple pomace, the inocula were transferred to a laboratory bioreactor (Biostat B Bonus, Sartorius) with a working volume of 2 L. Sterile apple juice (4° Brix) and silicone antifoam liquid to remove foaming were used for the batch fermentation. The cultivation conditions in the bioreactor for both yeast strains are shown in Table 1. Two batch tests were carried out for each strain. Yeast creams (109 cfu/ml) were stored at 4 °C before use.