Bacillus coagulans is a homofermentative, acid-tolerant and thermophilic sporogenic lactic acid bacterium, which is capable of producing high yields of optically pure lactic acid. The L-(+)-lactate dehydrogenase (L-LDH) from B. coagulans is considered as an ideal biocatalyst for industrial production. In this study, the gene IdhL encoding a thermostable L-LDH was amplified from B. coagulans NL01 genomic DNA and successfully expressed in Escherichia coil BL21 (DE3). The recombinant enzyme was partially purified and its enzymatic properties were characterized. Sequence analysis demonstrated that the L-LDH was a fructose 1,6-diphosphate-activated NAD-dependent lactate dehydrogenase (L-nLDH). Its molecular weight was approximately 34-36 kDa. The K-m and V-max values of the purified L-nLDH for pyruvate were 1.91 +/- 0.28 mM and 2613.57 +/- 6.43 mu mol (min mg)(-1), respectively. The biochemical properties of L-nLDH showed that the specific activity were up to 2323.29 U/mg with optimum temperature of 55 degrees C and pH of 6.5 in the pyruvate reduction and 351.01 U/mg with temperature of 55 degrees C and pH of 11.5 in the lactate oxidation. The enzyme also showed some activity in the absence of FDP, with a pH optimum of 4.0. Compared to other lactic acid bacterial L-nLDHs, the enzyme was found to be relatively stable at 50 degrees C. Ca2+, Ba2+, Mg2+ Mn2+ ions had activated effects on the enzyme activity, and the enzyme was greatly inhibited by Ni2+ ion. Besides these, L-nLDH showed the higher specificity towards pyruvate esters, such as methyl pyruvate and ethyl pyruvate. (C) 2014 Elsevier Inc. All rights reserved.