The organic acids in the culture filtrates were determined
by HPLC with a Beckman Interaction Ion 300 column
(7.8 mm ? 30 cm). Organic acids were monitored using a UV
detector at 220 nm. The mobile phase consisted of 0.014 N
sulfuric acid with a flow rate of 0.4 ml min ?1 (Kim et al., 1997).
There were eight independent replicate flasks for each isolate.