Biorefinery and Bioremediation Strategies for Efficient Management of Recalcitrant Pollutants Using Termites as an Obscure yet Promising Source of Bacterial Gut Symbionts: A Review.

Simple Summary: The accumulation of recalcitrant pollutants (e.g., lignin biomass and synthetic textile dyes) in diverse ecosystems has exacerbated the problem of environmental pollution. The complex polymer structure of lignin brings huge challenges to the development of high-efficiency transformation technology, making it difficult to realize its industrial utilization. On the other hand, the use of dyes in the textile industry poses significant challenges worldwide. Dyes are very similar to lignin biomass in chemical structure. Similarly, under natural conditions, it is difficult for microorganisms in the environment to achieve rapid biodegradation and complete detoxification. Clearly, the integration of bioremediation and biorefinery technology towards such recalcitrant organic wastes is considered a novel concept for mitigating the toxicity of such pollutants using termite gut symbionts. Modern biorefinery and bioremediation applications can integrate the termite gut system, a unique bioresource that comprises distinct bacterial species valued for lignocellulosic material processing and synthetic dye degradation. Therefore, this review paper provides a new strategy for efficient management of recalcitrant pollutants by exploring the potential application of termite gut bacteria in terms of science and industry. Lignocellulosic biomass (LCB) in the form of agricultural, forestry, and agro-industrial wastes is globally generated in large volumes every year. The chemical components of LCB render them a substrate valuable for biofuel production. It is hard to dissolve LCB resources for biofuel production because the lignin, cellulose, and hemicellulose parts stick together rigidly. This makes the structure complex, hierarchical, and resistant. Owing to these restrictions, the junk production of LCB waste has recently become a significant worldwide environmental problem resulting from inefficient disposal techniques and increased persistence. In addition, burning LCB waste, such as paddy straws, is a widespread practice that causes considerable air pollution and endangers the environment and human existence. Besides environmental pollution from LCB waste, increasing industrialization has resulted in the production of billions of tons of dyeing wastewater from several industries, including textiles, pharmaceuticals, tanneries, and food processing units. The massive use of synthetic dyes in various industries can be detrimental to the environment due to the recalcitrant aromatic structure of synthetic dyes, similar to the polymeric phenol lignin in LCB structure, and their persistent color. Synthetic dyes have been described as possessing carcinogenic and toxic properties that could be harmful to public health. Environmental pollution emanating from LCB wastes and dyeing wastewater is of great concern and should be carefully handled to mitigate its catastrophic effects. An effective strategy to curtail these problems is to learn from analogous systems in nature, such as termites, where woody lignocellulose is digested by wood-feeding termites and humus-recalcitrant aromatic compounds are decomposed by soil-feeding termites. The termite gut system acts as a unique bioresource consisting of distinct bacterial species valued for the processing of lignocellulosic materials and the degradation of synthetic dyes, which can be integrated into modern biorefineries for processing LCB waste and bioremediation applications for the treatment of dyeing wastewaters to help resolve environmental issues arising from LCB waste and dyeing wastewaters. This review paper provides a new strategy for efficient management of recalcitrant pollutants by exploring the potential application of termite gut bacteria in biorefinery and bioremediation processing. [ABSTRACT FROM AUTHOR]