A versatile peroxidase from Lentinus squarrosulus towards enhanced delignification and in vitro digestibility of crop residues

Abstract

The scarcity of quality feed is a major constraint to livestock productivity, and it is attributed to recalcitrant lignin, which hinders the utilization of crop residues. White-rot lignicolous fungi have been used for enrichment of crop residues through fungal pre-treatment, but dry matter loss is inevitable. Versatile peroxidase oxidizes a diverse class of aromatics without mediators and plays a key role in ligninolysis. In this study, the efficacy of a novel versatile peroxidase isolated from a wild species was evaluated for its effect in the delignification of crop residues. The strain identified as Lentinus squarrosulus (TAMI004, BankIt2098576 MH172167) demonstrated predominant versatile peroxidase activity amongst screened isolates in solid-state and submerged fermentations; it displayed hybrid characteristic of manganese oxidation and manganese independent reactions on aromatic compounds. The manganese oxidizing peroxidase activity was 12 U/mL in submerged and 131 U/mL in solid-state fermentation. Treatment of crop residues with L. squarrosulus extract rich in versatile peroxidase showed a decrease in neutral detergent fiber, acid detergent fiber, and acid detergent lignin contents, prompting delignification. Thus, the use of versatile peroxidase in enhancing the digestibility of straws for enhancing feed utilization for ruminants was substantiated.