A Novel Approach to Delignify Lignocellulosic Materials by Using Ligninolytic Enzyme Consortium

Lignin biodegradation is an attractive approach for producing value-added products. These valuable products are produced by the processing and refining of lignocellulosic residues. A set of ligninolytic enzymes including lignin peroxidase (LiP), manganese-dependent peroxidase (MnP), and laccase (Lac) were individually produced from Ganoderma lucidum, Trametes versicolor, and Pleurotus ostreatus. Solid state fermentation under pre-optimized culture conditions with varying ratios of enzymes were used for the delignification of lignocellulosic biomass residues. The fungal enzymes were purified in four steps including ammonium sulfate precipitation, dialysis, ion exchange chromatography, and gel filtration chromatography. The purified enzymes were subsequently used in varying ratios (with each containing 200 U/mL) for the delignification of wheat straw, sugarcane bagasse, and rice straw. The consortium of enzymes caused the removal of 58.5%, 46%, and 52% of the lignin from the wheat straw, sugarcane bagasse, and rice straw, respectively, at LiP: MnP: Lac ratios of 1:2:2, 1:1:2, and 2:1:2. The best delignification was observed in wheat straw (58.5%), exposing 76.54% cellulose content. The results suggested that the ligninolytic enzymes are effective catalysts for the selective partial delignification of lignocellulosic biomass residues. After delignification these lignocellulosic residues could be utilized as cost-effective substrates for the production of enzymes, biofuels, and other industrially significant products

Enzyme-treated Wheat Straw-based PVOH Bio-composites: Development and Characterization

Valorization of lignocellulosic waste residues in the development of potential biodegradable composites has been of recent research interest. Recent research has shown that wheat straw can be used as a reinforcement material for the synthesis of novel polyvinyl alcohol (PVOH)-based composites. However, certain pretreatment methodology needs to be used for the selective removal of the lignin component. The de-lignification of native wheat straw was performed using an in-house isolated ligninolytic consortium. The bio-composites were developed using the de-lignified wheat straw along with PVOH as the matrix phase and glycerol as a plasticizer via a compression molding technique. In this study, a structural analysis by Fourier transform infrared spectroscopy (FT-IR) showed that the enzymatic treatment led to noticeable changes in the chemical structure of the materials used. A dynamic mechanical analysis (DMA) of the composites revealed an increase in the tensile strength of the sample from 46.1 MPa ± 0.1 MPa to 53.0 MPa ± 0.9 MPa, upon the addition of the plasticizer. Also, there was a noticeable increase in the tensile modulus of composites from 2,130 MPa to 4,520 MPa, respectively. Topographical features of the newly synthesized PVOH-based bio-composites were observed using scanning electron microscopy