Expression and characterisation of feruloyl esterases from Lactobacillus fermentum JN248 and release of ferulic acid from wheat bran

Genes encoding six feruloyl esterases (FAEs; lbff0997, lbff0272, lbff1432, lbff1695, lbff1849, lbff0153) from Lactobacillus fermentum JN248 were cloned, overexpressed and characterised. Maximum enzyme activity was observed at 35 degrees C for recombinant FAEs LFFae0997, LFFae0272 and LFFae0153, at 30 degrees C for LFFae1695, and at 40 degrees C for LFFae1432and LFFae1849. For five of the enzymes, optimal activity was observed at pH 7.0 or pH 8.0, and high thermostability was measured up to 55 degrees C. By contrast, LFFae1432 lost less than 10.0% activity after incubation at 40 degrees C for 2 h, and pH stability was highest between pH 7.0 and pH 9.0. In addition, LFFae1432 was the most robust esterase, with a higher affinity and hydrolytic activity against synthetic esters. The enzymes released ferulic acids (FAs) from de-starched wheat bran (DSWB), and 60.7% of the total alkali-extractable FAs were released when LFFae1432 was added alone, compared with less than 10% for the other enzymes. The amount of FAs released by FAEs increased when combined with xylanase. These FAEs could serve as promising biocatalysts for biodegradation, and LFFae1432 may hold promise for potential industrial applications. (C) 2019 Elsevier B.V. All rights reserved.