The main aim of the present study was to enrich anaerobic mixed bacterial culture capable of producing ethanol from synthesis gas fermentation. Screening of thirteen anaerobic strains together with enrichment protocol helped to develop an efficient mixed culture capable of utilizing syngas for ethanol production. Physiological and operational parameters were optimized for enhanced ethanol production. The optimized value of operational parameters i.e. initial media pH, incubation temperature, initial syngas pressure, and agitation speed were 6.0 +/- 0.1, 37 degrees C, 2 kg cm (2) and 100 rpm respectively. Under these conditions ethanol and acetic acid production by the selected mixed culture were 1.54 g L (1) and 0.8 g L (1) respectively. Furthermore, up-scaling studies in semi-continuous fermentation mode further enhanced ethanol and acetic acid production up to 2.2 g L (1) and 0.9 g L (1) respectively. Mixed culture TERI SA1 was efficient for ethanol production by syngas fermentation. (C) 2014 Elsevier Ltd. All rights reserved.