Isolation of functional ligninolytic Bacillus aryabhattai from paper mill sludge and its lignin degradation potential

Recovery of green phenolic compounds from lignin-based source: Role of ferulic acid esterase towards waste valorization and bioeconomic perspectives

The production of chemicals/products so far relies on fossil-based resources with the creation of several environmental problems at the global level. In this situation, a sustainable and circular economy model is necessitated to mitigate global environmental issues. Production of biowaste from various processing industries also creates environmental issues which would be valorized for the production of industrially important reactive and bioactive compounds. Lignin acts as a vital part in biowaste composition which can be converted into a wide range of phenolic compounds. The phenolic compounds have attracted much attention, owing to their influence on diverse not only organoleptic parameters, such as taste or color, but also active agents for active packaging systems. Crop residues of varied groups, which are an affluent source of lignocellulosic biomass could serve as a renewable resource for the biosynthesis of ferulic acid (FA). FA is obtained by the FA esterase enzyme action, and it can be further converted into various tail end phenolic flavor green compounds like vanillin, vanillic acid and hydroxycinnamic acid. Lignin being renewable in nature, processing and management of biowastes towards sustainability is the need as far as the global industrial point is concerned. This review explores all the approaches for conversion of lignin into value-added phenolic compounds that could be included to packaging applications. These valorized products can exhibit the antioxidant, antimicrobial, cardioprotective, anti-inflammatory and anticancer properties, and due to these features can emerge to incorporate them into production of functional foods and be utilization of them at active food packaging application. These approaches would be an important step for utilization of the recovered bioactive compounds at the nutraceutical and food industrial sectors.

Bacterial transformation of lignin: key enzymes and high-value products

Lignin, a natural organic polymer that is recyclable and inexpensive, serves as one of the most abundant green resources in nature. With the increasing consumption of fossil fuels and the deterioration of the environment, the development and utilization of renewable resources have attracted considerable attention. Therefore, the effective and comprehensive utilization of lignin has become an important global research topic, with the goal of environmental protection and economic development. This review focused on the bacteria and enzymes that can bio-transform lignin, focusing on the main ways that lignin can be utilized to produce high-value chemical products. Bacillus has demonstrated the most prominent effect on lignin degradation, with 89% lignin degradation by Bacillus cereus. Furthermore, several bacterial enzymes were discussed that can act on lignin, with the main enzymes consisting of dye-decolorizing peroxidases and laccase. Finally, low-molecular-weight lignin compounds were converted into value-added products through specific reaction pathways. These bacteria and enzymes may become potential candidates for efficient lignin degradation in the future, providing a method for lignin high-value conversion. In addition, the bacterial metabolic pathways convert lignin-derived aromatics into intermediates through the "biological funnel", achieving the biosynthesis of value-added products. The utilization of this "biological funnel" of aromatic compounds may address the heterogeneous issue of the aromatic products obtained via lignin depolymerization. This may also simplify the separation of downstream target products and provide avenues for the commercial application of lignin conversion into high-value products.

Origin, Selection, and Succession of Coastal Intertidal Zone-Derived Bacterial Communities Associated with the Degradation of Various Lignocellulose Substrates

Terrestrial microbial consortia were reported to play fundamental roles in the global carbon cycle and renewable energy production through the breakdown of complex organic carbon. However, we have a poor understanding of how biotic/abiotic factors combine to influence consortia assembly and lignocellulose degradation in aquatic ecosystems. In this study, we used 96 in situ lignocellulose enriched, coastal intertidal zone-derived bacterial consortia as the initial inoculating consortia and developed 384 cultured consortia under different lignocellulose substrates (aspen, pine, rice straw, and purified Norway spruce lignin) with gradients of salinity and temperature. As coastal consortia, salinity was the strongest driver for assembly, followed by Norway spruce lignin, temperature, and aspen. Moreover, a conceptual model was proposed to demonstrate different succession dynamics between consortia under herbaceous and woody lignocelluloses. The succession of consortium under Norway spruce lignin is greatly related with abiotic factors, while its substrate degradation is mostly correlated with biotic factors. A discrepant pattern was observed in the consortium under rice straw. Finally, we developed four groups of versatile, yet specific consortia. Our study not only reveals that coastal intertidal wetlands are important natural resources to enrich lignocellulolytic degrading consortia but also provides insights into the succession and ecological function of coastal consortium.

Lignin-Degrading Bacteria in Paper Mill Sludge

The effluents generated in the paper industry, such as black liquor, have a high content of lignin and other toxic components; however, they represent a source of lignin-degrading bacteria with biotechnological potential. Therefore, the present study aimed to isolate and identify lignin-degrading bacteria species in paper mill sludge. A primary isolation was carried out from samples of sludge present in environments around a paper company located in the province of Ascope (Peru). Bacteria selection was made by the degradation of Lignin Kraft as the only carbon source in a solid medium. Finally, the laccase activity (Um-L^-1) of each selected bacteria was determined by oxidation of 2,2'-azinobis-(3-etilbencenotiazolina-6-sulfonate) (ABTS). Bacterial species with laccase activity were identified by molecular biology techniques. Seven species of bacteria with laccase activity and the ability to degrade lignin were identified. The bacteria Agrobacterium tumefasciens (2), Klebsiella grimontii (1), and Beijeinckia fluminensis (1) were reported for first time. K. grimowntii and B. fluminensis presented the highest laccase activity, with values of 0.319 ± 0.005 UmL^-1 and 0.329 ± 0.004 UmL^-1, respectively. In conclusion, paper mill sludge may represent a source of lignin-degrading bacteria with laccase activity, and they could have potential biotechnological applications.