Cellular redox status and oxygen availability influence the product formation. Herein, decreasing agitation speed or adding vitamin C (Vc) achieved the 2,3-BDL yield of 0.40 g g(-1) or 0.39 g g(-1) glucose under batch fermentation, respectively. To our knowledge, this is the highest 2,3-BDL yield reported so far for Paenibacillus polymyxa without adding acetic acid. The NADH/NAD(+) ratio and 2,3-BDL titer could be increased significantly by reducing the agitation speed or adding Vc, indicating that the enhancement of 2,3-BDL is closely associated with the adjustment of NADH/NAD(+) ratio. Especially, Vc addition elevated the 2,3-BDL titer from 43.66 g L-1 to 71.71 g L-1 within 54 h under fed-batch fermentation. This is the highest titer of 2,3-BDL so far reported for P. polymyxa from glucose fermentation. This work provides a new strategy to improve 2,3-BDL production and helps us to understand the responses of P. polymyxa to extracellular oxidoreduction potential. (C) 2014 Elsevier Ltd. All rights reserved.