2.2. Growth media and starter culture preparation
Starter cultures of D. bruxellensisstrains were prepared by transferring multiple colonies from YPD agar into 5 ml YPD broth in sterile 14 ml tubes, and then incubating at 27 C for 48 h. These cultures were used to inoculate either yeast nitrogen base (YNB, Difco) (yeast nitrogen base, 67 g/l; glucose, 20 g/l; pH 3.5) or YPD-ethanol adaptation media containing 6% (v/v)ethanol, at5 10 6 cells/ml according to experimental requirements. YNB or YPD-ethanol adaptation cultures (100 ml in 250 ml shake fl ask) were incubated at 27 C with agitation (150 rpm) until a density of 1 10 8 cells/ml was achieved according to duplicate haemocytometer counts.Chemically de fi ned wine medium (WM) was prepared by fermentation of chemically de fi ned grape juice medium (McBryde et al., 2006) with a wine yeastPDM as described in Harris et al.(2008) Finished wine was adjusted to 10% (v/v) ethanol after concentration was determined using an Anton Paar Alcolyzer according to the manufacturer s instructions and pH modi fi ed to 3.8 using 10 M NaOH. Residual sugar concentration was determined by glucose-fructose enzymatic assay (Boehringer Mannheim), and then adjusted to 2.5 g/l glucose and 2.5 g/l fructose. To ensure de fi ciency problems were avoided, vitamins were also added(Harris et al., 2008). Complete WM was sterilized byfi ltration(0.22mm, Millipore)