AUTHOR=Xu Zhenshang , Kong Jian , Zhang Susu , Wang Ting , Liu Xinli TITLE=Comparison of Enzyme Secretion and Ferulic Acid Production by Escherichia coli Expressing Different Lactobacillus Feruloyl Esterases JOURNAL=Frontiers in Microbiology VOLUME=Volume 11 - 2020 YEAR=2020 URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.568716 DOI=10.3389/fmicb.2020.568716 ISSN=1664-302X 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 produce ferulic acid from agricultural waste. A total of ten 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 Lb. acidophilus and Lb. johnsonii. The second type showed a high secretion level, including feruloyl esterases derived from Lb. amylovorus, Lb. crispatus, Lb. gasseri and Lb. helveticus. The third type also behaved a high secretion level but easy degradation, including feruloyl esterases derived from Lb. farciminis, Lb. fermentum and Lb. 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 Lb. amylovorus feruloyl esterase. These results provided a solid basis for production of feruloyl esterase and ferulic acid.