Tetracycline pollution is a growing global threat to aquatic and terrestrial biodiversity due to its unprecedented use in aquaculture, livestock, and human disease prevention. The influx of tetracycline may annihilate the microbial ecology structure in the environment and pose a severe threat to humans by disturbing the food chain. Although significant research data are available in the literature on various aspects of tetracycline, including detection techniques, degradation mechanisms, degradation products, and policy statements to curtail the issue, there is a scarcity of a report to compile the recent data in the literature for better analysis and comparison by the policymakers. To achieve this paucity in knowledge, the current study aims at collecting data on the available degradation strategies, mechanisms involved in biodegradable and non-biodegradable routes, the main factor affecting degradation strategies, compile novel detection techniques of tetracycline antibiotics in the environment, discuss antibiotic resistance genes and their potential role in degradation. Finally, limitations in the current bioremediation techniques and the future prospects are discussed with pointers for the decision-makers for a safer environment.

The biorefining technology for biofuels and chemicals from lignocellulosic biomass has made great progress in the world. However, mobilization of laboratory research toward industrial setup needs to meet a series of criteria, including the selection of appropriate pretreatment technology, breakthrough in enzyme screening, pathway optimization, and production technology, etc. Extremophiles play an important role in biorefinery by providing novel metabolic pathways and catalytically stable/robust enzymes that are able to act as biocatalysts under harsh industrial conditions on their own. This review summarizes the potential application of thermophilic, psychrophilic alkaliphilic, acidophilic, and halophilic bacteria and extremozymes in the pretreatment, saccharification, fermentation, and lignin valorization process. Besides, the latest studies on the engineering bacteria of extremophiles using metabolic engineering and synthetic biology technologies for high-efficiency biofuel production are also introduced. Furthermore, this review explores the comprehensive application potential of extremophiles and extremozymes in biorefinery, which is partly due to their specificity and efficiency, and points out the necessity of accelerating the commercialization of extremozymes.

Worldwide industrial development has released hazardous polycyclic aromatic compounds into the environment. These pollutants need to be removed to improve the quality of the environment. Chemotaxis mechanism has increased the bioavailability of these hydrophobic compounds to microorganisms. The mechanism, however, is poorly understood at the ligand and chemoreceptor interface. Literature is unable to furnish a compiled review of already published data on up-to-date research on molecular aspects of chemotaxis mechanism, ligand and receptor-binding mechanism, and downstream signaling machinery. Moreover, chemotaxis-linked biodegradation of aromatic compounds is required to understand the chemotaxis role in biodegradation better. To fill this knowledge gap, the current review is an attempt to cover PAHs occurrence, chemical composition, and potential posed risks to humankind. The review will cover the aspects of microbial signaling mechanism, the structural diversity of methyl-accepting chemotaxis proteins at the molecular level, discuss chemotaxis mechanism role in biodegradation of aromatic compounds in model bacterial genera, and finally conclude with the potential of bacterial chemotaxis for aromatics biodegradation.

Hydrothermal liquefaction (HTL) technology has garnered immense research interest due to its potential to convert wet biomass into petroleum-like biocrude. Understanding the reaction mechanism and kinetics of HTL is crucial for understanding the process better, estimating the yields, and scaling up. On the other hand, reaction mechanisms and kinetics largely depend upon the feedstock composition and reaction parameters of HTL. However, the literature lacks an in-depth analysis of the reaction mechanism and kinetics concerning biocrude yield and product distribution for a single to multi-feedstock scenario. This review focuses on the reaction mechanisms of various biomolecular components of lignocellulosic biomass, proteins, and lipids in the HTL process under sub- and supercritical conditions. Furthermore, the HTL reaction kinetics, effect of reaction conditions on reaction mechanisms, and product distribution are explored. The findings agree that reaction temperature and retention time follow inverse relations for high biocrude yield. A high heating rate is recommended for higher biocrude yield to avoid cracking and recombination processes. A high solvent/feedstock ratio, depending on feedstock composition, was favored for optimum biocrude yield. In addition, catalysts and reaction solvents, especially organic solvents, effectively contribute towards high biocrude yield, even up to 70%. Heterogeneous catalysts are favored due to reusability and improved biocrude quality. Also, hydrothermal co-liquefaction (multi-feedstock) use for improving biocrude yield was debated. A detailed discussion on the reaction kinetics of various biomolecular components in the HTL process revealed that reactions in HTL normally follow the first-order rate law. Finally, the authors outline the pointers for future research in HTL for industrial upscaling.