Bio-valorization of lignin from Kraft pulp mills through establishment of Pulp-Ligcon metagenome sequencing

Abstract

Lignin is the primary by-product of pulp and paper industry (kraft pulp mills). Hybrids of Eucalyptus grandis x E. urophylla are mainly used to make fiberboards, pulp, and papermaking industries in Brazil. For kraft pulp production, Eucalyptus wood is heated in an alkaline medium to solubilize the lignin. Solubilized lignin which is also known as black liquor, is concentrated and burnt to produce energy in the recovery boiler. Thus, cellulose is separated and after various processing steps is used for making paper. Suzano S/A and Klabin S/A are the two major pulp and paper companies in Brazil, producing a large amount of lignin for energy and high value-based commercial products. Approximately, 55 million tons of lignin are produced by the pulp industry. Currently, modern pulp mills generate their thermal energy demands and sell excess energy as electricity by burning lignin. However, lignin could be vastly applied for the different range of applications such as carbon fibers, activated carbon, adhesives, resins, and others. In this project, lignin from pulp industry will be used as a carbon and energy source during bacterial cultivation in a sustainable manner. Additionally, metagenomic discovery platform will be established from pulp mills community enrichment protocols, to depict bacterial biocatalysts and pathways involved in lignin degradation and aromatic compound conversion. Eventually, in order to prove the application of the metagenomic strategy, biotransformation of kraft lignin components into sustainable products of industrially relevance from such as polyhydroxyalkanoate (PHA), biolipids and biogas. The genes obtained after metagenomic sequencing will be synthesized, cloned and expressed into Escherichia coli and Yarrowia lipolytica for PHA and biolipids production, respectively. Biogas production will be assessed from kraft lignin using sewage water inoculum. Further, the enriched microbial consortium developed will be tested for the biodegradation of low-density polyethylene films into simpler monomers. The lignin degradation profile will be evaluated by gel permeation chromatography (GPC), Liquid chromatography couple to mass spectrophotometry (LC-MS), thermogravimetric analysis (TGA), FTIR, NIR, NMR, Raman (spectroscopy), field emission SEM, AFM and, XRD. A systematic techno-economic analysis will be performed to determine the technical and economic viability for commercial-scale process of lignin recovery, purification and bioconversion. (AU)