The separation of organic acid was achieved using Shimadzu UFLC system (Shimadzu Corporation, Kyoto, Japan) equipped with ODS‐3 column (Shim‐pack, 150 × 4.6 mm). Twenty microliter of filtered supernatant fractions was injected. Organic acid was separated isocratically at 0.7 ml/min, at 65°C, using 10 mmol/L H2SO4 as the mobile phase. Lactic, acetic, formic, oxalic, citric, succinic, propionic, and butyric acids were detected at 210–280 nm with PDA detector (SPD‐M20A, Shimadzu, Japan). Individual organic acids were identified and quantified using external standards (Sigma Aldrich, Supelco, St. Louis, USA). Quantification of organic acids was performed from the standard curves obtained using five‐point solutions of predetermined concentrations. Triplicate extractions and injections were conducted for each sample.