To prepare inoculums for each fermentation experiment,a loop of cell was transferred from an agar slant to a 50 mL culture tube containing 10 mL of a medium modified from that used by Mandel and Weber with 10 g glucose/L in place of cellulose.With the cap slightly loosened,the culture tube was shaken at 250 rpm for mixing and gas transfer.Cell were grown in the tube for 5-6 days at room temperature before being transferred to a 250 mL flask containing 50 mL of the same medium.The cell in the flask were similarly cultured on shaker for 4 day and used as the inoculums to a 3 L flask containing 1 L of a defined medium,which had either 10 g glucose/L or 5 g glucose/L plus 5 g/L of Avicel as the C-substrate,similar to that used by Tangnu