5% of samples will be enriched in 25 mL YPD medium (yeast extract 10 g/L and
276 Suleeporn Kitcha and Benjamas Cheirsilp / Energy Procedia 9 ( 2011 ) 274 – 282
peptone 10 g/L) by using 40 g/L glucose or glycerol as a carbon source at acid pH (4.0) or neutral pH
(6.0) with 0.0001% chloramphenicol