Extracellular secretion of feruloyl esterase derived from Lactobacillus crispatus in Escherichia coli and its application for ferulic acid production.

A feruloyl esterase producing strain was isolated and identified as Lactobacillus crispatus S524. Its putative feruloyl esterase was heterogeneously expressed in Escherichia coli BL21 (DE3). Interestingly, the feruloyl esterase (FaeLcr) could be secreted into the culture medium with a relative high purity of 201.7 mg/L. FaeLcr was purified from the cell-free culture supernatant and appeared as a single protein band with the molecular mass of 28 kDa by SDS-PAGE. The optimal temperature and pH were determined as 65 °C and 7.0, and it showed prominent thermo-stability and alkali-stability. Furthermore, the purified FarLcr could release a maximal amount of 199 µg ferulic acid from 0.2 g de-starched wheat bran. Meanwhile, when cultured this recombinant E. coli strain in medium supplemented with 2 g de-starched wheat bran, 1.86 mg ferulic acid was also detected. These results suggested that the recombinant strain has a great potential application in feruloyl esterase and ferulic acid production.