Bacterial beta-1,3-1,4-glucanase (BG) is an endoglucanase that hydrolyzes linear beta-glucans containing beta-1,3 and beta-1,4 linkages, such as barley beta-glucans. In this study, a BG gene was transformed into the food-grade plasmid pNZ8149 and successfully expressed in Lactococcus lactis NZ3900 using the nisin-controlled gene expression system. To facilitate extracellular secretion, the signal peptide Usp45 was added during vector construction. A histidine tag was also added for affinity purification. BG was extracellularly secreted and was also present in the cells in soluble form. N-terminal amino acid residue analysis of secreted BG revealed that the Usp45 peptide was removed. The optimum temperature and pH for both intracellular and extracellular BG were 40 degrees C and 6, respectively. The enzyme kinetic parameters, V-max, K-m, k(cat), and k(cat)/K-m, of extracellular BG were 1317.51 mu mol min(-1), 1.97 mg ml(-1), 588.54 s(-1), and 298.26 ml s(-1).mg(-1), respectively. There was no significant difference in the enzyme kinetic parameters of intracellular and extracellular BG. The growth pattern of transformed L. laths NZ3900 in beta-glucan-containing liquid medium confirmed beta-glucan degradation by BG. The transformed strain degraded beta-glucans, produced gluco-oligosaccharide, and produced lactic acid. The strain and expression system constructed in this study could be applied to industrial fields requiring BG produced in foodgrade lactococcal secretory expression system.