Biological treatment methods overcome many of the drawbacks of physicochemical strategies and play a significant role in removing dye contamination for environmental sustainability. Numerous microorganisms have been investigated as promising dye-degrading candidates because of their high metabolic potential. However, few can be applied on a large scale because of the extremely harsh conditions in effluents polluted with multiple dyes, such as alkaline pH, high salinity/heavy metals/dye concentration, high temperature, and oxidative stress. Therefore, extremophilic microorganisms offer enormous opportunities for practical biodegradation processes as they are naturally adapted to multi-stress conditions due to the special structure of their cell wall, capsule, S-layer proteins, extracellular polymer substances (EPS), and siderophores structural and functional properties such as poly-enzymes produced. This review provides scientific information for a broader understanding of general dyes, their toxicity, and their harmful effects. The advantages and disadvantages of physicochemical methods are also highlighted and compared to those of microbial strategies. New techniques and methodologies used in recent studies are briefly summarized and discussed. In particular, this study addresses the key adaptation mechanisms, whole-cell, enzymatic degradation, and non-enzymatic pathways in aerobic, anaerobic, and combination conditions of extremophiles in dye degradation and decolorization. Furthermore, they have special metabolic pathways and protein frameworks that contribute significantly to the complete mineralization and decolorization of the dye when all functions are turned on. The high potential efficiency of microbial degradation by unculturable and multi-enzyme-producing extremophiles remains a question that needs to be answered in practical research.

Sustainable management of organic waste, such as food waste (FW) and livestock manure (LS), is essential for reducing pollution and promoting resource recycling. This study investigated the effects of Bacillus sp. inoculation and biochar addition on composting efficiency, microbial dynamics, and physicochemical properties. Bacillus sp. accelerated the breakdown of cellulose and lignin, reduced moisture content, stabilized pH, and mitigated ammonia volatilization. Biochar reduced ammonia emissions by 17.04%, increasing to 28.89% with Bacillus sp. Next-generation sequencing revealed Bacillus sp. enhanced microbial diversity, suppressed pathogens, and promoted beneficial microbial interactions. LS treatments retained Firmicutes dominance (up to 95.17%), improving nitrogen retention, while FW treatments transitioned to Proteobacteria and Bacteroidota, driving plant material decomposition. By day 35, Bacillus sp. increased late-stage microbial taxa (Deinococcota, Myxococcota), linked to cellulose degradation and pathogen suppression. In FW biochar compost (FWBC), Planococcaceae and Bacillaceae synergistically decomposed complex organic matter. LS biochar compost (LSBC) reduced anaerobic families like Clostridiaceae and Peptostreptococcaceae, lowering methane and hydrogen sulfide emissions. Microbial network analysis highlighted improved cooperation under Bacillus sp., with LSBC sustaining positive interactions at higher dosages. These results demonstrate that microbial inoculants and biochar enhance composting efficiency, nutrient cycling, and environmental sustainability.

The brightly colored synthetic dyes used in the textile industry are discharged at high concentrations—for example, various azo dyes including Methylene Blue (MB) and Methyl Orange (MO)—which is a matter of global concern, as such dyes are harmful to humans and the environment. Microbial degradation is considered an efficient alternative for overcoming the disadvantages of conventional physical and chemical dye removal methods. In this study, we investigated the potential of multiple types of the enzyme-producing extremophilic bacteria Bacillus FW2, isolated from food waste leachate, for the decolorization and bioremediation of artificial synthetic dyes. The screening of enzyme production and assaying of bacterial strain enzymes are essential for enhancing the breakdown of azo bonds in textile azo dyes. The degradation efficiencies of the water-soluble dyes MB and MO were determined at different concentrations using rice husk, which is an efficient substrate. Using the rice husks, the MO was removed completely within 20 h, and an estimated 99.8% of MB was degraded after 24 h by employing shaking at 120 rpm at 40 °C—whereas a removal efficiency of 98.9% was achieved for the combination of MB + MO. These results indicate the possibility of applying an extremophilic bacterial strain, Bacillus sp., for large-scale dye degradation in the future.