A novel Versatile Peroxidase from Lentinus squarrosulus (MH172167)towards enhanced delignification and digestibility of crop residues

Abstract

Scarcity of quality feed is a major constraint concerning livestock productivity with recalcitrant lignin hindering utilization of crop residues as quality animal feed. Degradation of lignin in nature is contributed by white-rot fungi through their enriched ligninolytic system. Versatile Peroxidase plays a key role in ligninolysis through its capability to oxidize diverse class of aromatics without mediators. In this study, wild isolates of wood rotting fungi were screened for potential peroxidases oxidizing manganese and aromatic compounds. The strain identified as Lentinus squarrosulus (TAMI004, BankIt2098576 MH172167) was monitored for enzyme activity in solid state and submerged fermentation. L. squarrosulus demonstrated predominant Versatile Peroxidase activity amongst the screened wild isolates displaying hybrid characteristic of manganese oxidation and manganese independent reactions on aromatic compounds. The manganese oxidizing peroxidase activity evidenced in submerged fermentation was 12 IU/L whereas in solid state fermentation it was 131 IU/L. This ability to act through manganese mediated and independent reactions on phenolics reveals its biotechnological and industrial significance. Treatment of common crop residues with crude extract of L. squarrosulus rich in Versatile Peroxidase obtained from both Solid state and submerged fermentations showed a decrease in their Neutral Detergent Fiber, Acid Detergent Fiber and Acid Detergent Lignin content showing biodegradation, substantiating the ligninolytic ability and more prominently increase in their digestibility. To the best of our knowledge, this is the first report describing Versatile Peroxidase from Lentinus squarrosulus with potential to augment the ruminant digestibility of crop residues.\n\nImportanceVersatile Peroxidase of White-rot fungi, a relatively less studied lignolytic enzyme, is very efficient in depolymerization of lignin macromolecule through its multivalent catalytic sites. Lignin degradation is very appealing from the application perspective as attack on lignin exposes the energy affluent polysaccharides for utilization in extensive biotechnological applications. Reports on relevance of Versatile Peroxidase for these purposes are still emerging, however the role of ligninolytic enzymes especially Versatile Peroxidase in enriching ruminant feed is yet unturned. Here, this work demonstrates the potential of Versatile Peroxidase from a novel species Lentinus squarrosulus in delignification thereby upgrading the digestibility and nutritive value of crop residues. The observations validate the importance of the enzyme in improvement of crop residues for feeding ruminants in the current scenario where, livestock productivity is severely impacted by lack of quality feed and demand for alternate feed resources is intensifying.