Characteristics of a Recombinant Lentinula edodes Ferulic Acid Esterase and Its Adverse Effects on In Vitro Fermentation of Wheat Straw

Abstract

Ferulic acid esterases belong to the category of carboxylesterases and possess the capability to enzymatically break down hemicellulose within lignocellulosic substances, thereby liberating ferulic acid. A ferulic acid esterase from Lentinula edodes (LeFae) was expressed using Pichia pastoris, and its characterization and effects on the in vitro fermentation of wheat straw were investigated in this study. The optimal pH and temperature for LeFae were pH 7.0 and 60 °C, respectively. LeFae exhibited a broad temperature and pH adaptability (>60% of the maximum activity at pH 4.0–7.0 and 40–70 °C) and excellent thermal stability. The activity of LeFae was increased by 30.3% with a dosage of Tween 20 at 0.25% (v/v) and exhibited satisfactory resistance to Mn2+ and sodium dodecyl sulfate. LeFae released ferulic acid from wheat straw and exhibited an obvious synergistic effect with cellulase during wheat straw hydrolysis. LeFae severely inhibited the microbial fermentation of wheat straw and reduced the in vitro dry matter digestibility, total volatile fatty acid yield, and 16S rDNA copy numbers of Ruminococcus flavefaciens by 9.6%, 9.9 mM, and 40.1%, respectively. It also increased pH and the concentration of soluble phenols during wheat straw fermentation. Pretreating wheat straw with LeFae did not affect the microbial fermentation of wheat straw but resulted in the leaching of more dissolving sugars. The current results showed that although LeFae can cooperate with cellulase to promote the hydrolysis of wheat straw, its adverse effect on rumen microorganisms when directly fed to ruminants is a problem worthy of consideration.