Bacterial valorization of kraft lignin for PHA production through metagenomic sequencing of pulp-ligcon microbial community

Abstract

This Ph.D. project proposal will develop a sustainable process for the production of polyhydroxyalkanoates (PHA) from the kraft lignin (Suzano Papel e Celulose). This biotechnological process aims at integration with the pulp and paper industry in a biorefinery context. For the success of this research, solid knowledge of Applied Microbiology and Conversion of Lignocellulosic Biomass generated in the Department of Industrial Biotechnology of the Escola de Engenharia de Lorena - USP will be used. Most of the traditional research lines in the department take advantage of the cellulose and hemicellulose fractions for the production of different bioproducts from yeasts and fungi. However, the present study will be the first of its kind for the biological conversion of kraft lignin using isolated wild bacteria for PHA production. Consequently, it will help to consolidate a new research line in the department. PHA comprises a group of naturally biodegradable polyesters that are synthesized by microorganisms, main bacteria, such as Pseudomonas putida, Ralstonia eutropha, Pandoraea sp., Cupriavidus basilensis, and others. This molecule opens the doors for a sustainable future in the production of bioplastics and synthetic plastic replacement. Therefore, the project contemplates the collection of kraft lignin samples, and the evaluation of different treatment conditions to depolymerize and recover the lignin fragments. All lignin samples before and after the treatments will be characterized physicochemically by suitable methods. Concomitantly, a pulp-ligcon microbial consortium with high activity for degradation of kraft lignin will be developed. From this microbial community, high-throughput screening of new bacterial lignin degraders will be performed using lignin-degrading enzyme activities. Subsequently, each isolated bacterial strain will be identified through the 16S ribosomal region. In relation to the metagenomic analysis, the global DNA content in the bacterial consortium will be studied for genetic model prediction, bacterial genomes, and metabolic pathways involved in lignin degradation. Based on these results, the metabolic pathways for kraft lignin conversion into PHA will be identified. Hence, the cloning and expression of the genes in Escherichia coli BL21 involved in the fermentative production of PHA will be adopted as a strategy. It is expected that the scientific findings will contribute significantly to the diversification of bioproducts from the pulp and paper industry for the use of kraft lignin, having PHA as a high value-added co-product within a biorefinery. (AU)