Lactate-utilizing bacteria play important roles in the production of Chinese strong-flavored liquor (CSFL). However, the identity of these bacteria and their lactate-utilizing properties are largely unknown. Here, a lactate-utilizing, butyrate-producing bacterium BPY5 was isolated from an old fermentation pit for CSFL production. The isolate represented a novel species belonging to Clostridium cluster XIVa of family Lachnospiraceae based on phylogenetic analysis using 16S rRNA gene sequences. Strain BPY5 could ferment lactate into butyrate as the major metabolic product. Butyrate was significantly formed at initial lactate concentration from 66 to 104 mM, but substantially declined when initial lactate exceeded 133 mM. At initial lactate concentration of 66 mM, lactate conversion was independent on initial pH from 5.5 to 7.0, but the conversion was completely inhibited when pH dropped below 4.8. Nevertheless, the inhibition on lactate conversion was largely relieved by the addition of acetate, suggesting that exogenous acetate could enhance lactate conversion at low pH condition. Additionally, lactate in CSFL-brewing wastewater was dramatically removed when inoculated with strain BPY5. These results implicate that the isolate may be applied for the industrial production of butyrate or the recovery of butyrate from lactate-containing wastewater.