2.1 Materials
Ethylene glycol (EG), 1,3-propylene glycol (1,3-PG), 1,4-butylene glycol (1,4-BG), 1,5-pentylene glycol (1,5-PG) and 1,6-hexylene glycol (1,6-HG) were obtained from Aladdin Chemical Reagent Corporation. Yeast Extract was purchased from Sigma-Aldrich. Sorbitol, MgSO4, KH2PO4, K2HPO4, (NH4)2SO4 and CaCO3 were obtained from Sinopharm Chemical Reagent Co., Ltd. (China). All other chemicals were of analytical grade and were commercially available.