Characterization of a Feruloyl Esterase from Lactobacillus plantarum

Abstract

bLactobacillus plantarum is frequently found in the fermentation of plant-derived food products, where hydroxycinnamoyl esters are abundant. L. plantarum WCFS1 cultures were unable to hydrolyze hydroxycinnamoyl esters; however, cell extracts from the strain partially hydrolyze methyl ferulate and methyl p-coumarate. In order to discover whether the protein Lp_0796 is the enzyme responsible for this hydrolytic activity, it was recombinantly overproduced and enzymatically characterized. Lp_0796 is an esterase that, among other substrates, is able to efficiently hydrolyze the four model substrates for feruloyl esterases (methyl ferulate, methyl caffeate, methyl p-coumarate, and methyl sinapinate). A screening test for the detection of the gene encoding feruloyl esterase Lp_0796 revealed that it is generally present among L. plantarum strains. The present study constitutes the description of feruloyl esterase activity in L. plantarum and provides new insights into the metabolism of hydroxycinnamic compounds in this bacterial species. Phenolic acids are abundant, naturally occurring molecules that contribute to the rigidity of plant cell walls. Hydroxycinnamic acids, such as ferulic, sinapic, caffeic, and p-coumaric acids, are found both covalently attached to the cell wall and as soluble forms in the cytoplasm. Esters and amides are the most frequently reported types of conjugates, whereas glycosides occur only rarely (1). Hydroxycinnamates are found in numerous plant foods and in significant quantities in agroindustry-derived by-products. The industrial use of hydroxycinnamates has attracted growing interest since they and their conjugates were shown to be bioactive molecules possessing potential antioxidant activities and health benefits. The removal of these phenolic compounds and the breakdown of the ester linkages between polymers allow their exploitation for numerous industrial and food applications.Feruloyl esterases, also known as ferulic acid esterases, cinnamic acid esterases, or cinnamoyl esterases, are the enzymes involved in the release of phenolic compounds, such as ferulic, pcoumaric, caffeic, and sinapic acids, from plant cell walls (2). In human and ruminal digestion, feruloyl esterases are important to de-esterify dietary fiber, releasing hydroxycinnamates and derivatives, which have been shown to have positive effects, such as antioxidant, anti-inflammatory, and antimicrobial activities (3). They are also involved in colonic fermentation, where their activities in the microbiota improve the breakdown of ester bonds in hydroxycinnamates (3). The biological properties of hydroxycinnamates depend on their absorption and metabolism. Although there is evidence that food hydroxycinnamates are degraded by the gut microbiota, only limited information on the microorganisms and enzymes involved in this degradation is currently available.Feruloyl esterases able to hydrolyze hydroxycinnamates have been found in lactic acid bacteria isolated from foods and from the human intestinal microbiota, such as some str...

A Lactobacillus plantarum Esterase Active on a Broad Range of Phenolic Esters

“…For the degradation assays, the L. plantarum strains were cultivated in a modified basal and defined medium for L. plantarum described previously (18,25).…”

“…However, the definite approach to assigning a molecular function to a predicted open reading frame is to isolate and biochemically characterize the corresponding protein (14). In this regard, a wide study to dissect the complex array of esterase activities in L. plantarum WCFS1 cells was designed by our group (15)(16)(17)(18)(19)(20)(21)(22)(23). From the esterases assayed, only Lp_0796 was able to hydrolyze hydroxycinnamic acids and was therefore considered a feruloyl esterase.…”

An unusual feruloyl esterase belonging to family VIII esterases and displaying a broad substrate range

“…EstG34 had a specific activity of 10.3 U mg -1 , 0.65 U mg -1 and 0.11 U mg -1 on these substrates, respectively (Supplementary Figure S4). While there are relatively few characterised feruloyl esterases in the literature [43,44,45] EstG34 activity is comparable to two characterised fungal feruloyl esterases [46].…”

Identification and major technological characteristics of Lactococcus and Lactobacillus strains isolated from hamoum, an Algerian fermented wheat

“…L. lactis exhibits a stronger esterase activity than that of L. plantarum according to Macedo et al (2003) and Karam et al (2012), which confirms the results of the present study. Several studies have characterized the esterases of L. plantarum (Gobbetti et al, 1997;Brod et al, 2009;Esteban-Torres et al, 2013Kim et al, 2017). The lipolytic activity of L. brevis remains the lowest with ratios (h/c) not exceeding 3.…”