Maltose, glucose, acetic acid and lactic acid were determined by using High Performance Liquid Chromatography (HPLC) (Agilent 1200 series, Agilent Technologies, Germany) equipped with an Aminex HPX 87H column (Bio-Rad, Hercules, USA) at a pressure of 52 bar with H2SO4 10 mM as eluent according to the provider's instruction.