Comparison of Enzyme Secretion and Ferulic Acid Production by Escherichia coli Expressing Different Lactobacillus Feruloyl Esterases

Abstract

Construction of recombinant Escherichia coli strains carrying feruloyl esterase genes for secretory expression offers an attractive way to facilitate enzyme purification and one-step production of ferulic acid from agricultural waste. A total of 10 feruloyl esterases derived from nine Lactobacillus species were expressed in E. coli BL21 (DE3) to investigate their secretion and ferulic acid production. Extracellular activity determination showed all these Lactobacillus feruloyl esterases could be secreted out of E. coli cells. However, protein analysis indicated that they could be classified as three types. The first type presented a low secretion level, including feruloyl esterases derived from Lactobacillus acidophilus and Lactobacillus johnsonii. The second type showed a high secretion level, including feruloyl esterases derived from Lactobacillus amylovorus, Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus helveticus. The third type also behaved a high secretion level but easy degradation, including feruloyl esterases derived from Lactobacillus farciminis, Lactobacillus fermentum, and Lactobacillus reuteri. Moreover, these recombinant E. coli strains could directly release ferulic acid from agricultural waste. The highest yield was 140 μg on the basis of 0.1 g de-starched wheat bran by using E. coli expressed L. amylovorus feruloyl esterase. These results provided a solid basis for the production of feruloyl esterase and ferulic acid.

The N-terminus of Lactobacillus amylovorus feruloyl esterase plays an important role in its secretion by Lactobacillus plantarum and Escherichia coli

“…Our previous experiments showed that FaeLam could be secreted from strain E. coli BL21(DE3) [ 11 ]. In the present study, it could also be secreted into extracellular environment of E. coli DH5α, suggesting the secretion of FaeLam is not strain dependent.…”

“…Thus, the feruloyl esterase could be classified as non-classically secreted protein, which seldom reported in lactic acid bacteria [ 32 ]. In our previous study, we found that ten feruloyl esterases produced by different lactic acid bacteria all could be secreted by E. coli , although with diverse secretion levels [ 11 ]. Sequence alignment showed that the N20 of these enzymes had a certain similarity, especially conserved in two leucine and a glycine (Additional file 1 : Figure S6).…”

“…The hydrolytic zone was examined and photographed. Furthermore, the ρNPF was used as substrate to quantitatively determine the feruloyl esterase activity according to our previous work [ 11 ].…”

“…The hydrolytic zone was examined and photographed. Furthermore, the ρNPF was used as substrate to quantitatively determine the feruloyl esterase activity according to our previous work [11]. High performance liquid chromatography (HPLC) method was also employed to detect the hydrolytic activity of feruloyl esterase.…”

“…However, the common laboratory strains of E. coli are poor secretors for proteins, resulting from the complex cell envelope with two layers [ 10 ]. Unexpectedly, our previous study showed that the high yield of feruloyl esterase (FaeLam derived from L. amylovorus ) could be secreted from E. coli BL21(DE3) with the pET expression system [ 11 ]. Despite the several reports about secretory proteins in E. coli , there is no conclusive and universally secretion pathway identified so far [ 12 , 13 ].…”