We are now entering the third decade of the 21st Century, and, especially in the last years, the achievements made by scientists in the field of Microbiology have been exceptional, leading to major advancements. Frontiers has organized a series of Research Topics to highlight the latest advancements in science in order to be at the forefront of science in different fields of research. This specific editorial initiative, led by Dr. Ruiyong Zhang is focused on new insights, novel developments, current challenges, latest discoveries, recent advances and future perspectives in the field.

Molecular hydrogen (H2) is an important molecule in the metabolism of diverse microorganisms. It is used either as energy source or for the disposal of reducing equivalents depending on environmental conditions. Furthermore, H2 transmits energy between different species within microbial communities. The enzymes that split or evolve H2 are called hydrogenases and these metalloproteins can be divided into three phylogenetically unrelated classes distinguishable by the metal composition of their active sites, namely [Fe]-, [FeFe]-, and [NiFe]- hydrogenases. Following a century of hydrogenase research, it is now possible to isolate, handle, and investigate these fragile enzymes. There have been numerous advances in understanding the regulation, function, structures, and maturation of these enzymes, as well as their involvement in important processes such as microbial pathogenesis and biogeochemical cycling. The employment of hydrogenases and hydrogenase-based applications could also potentially facilitate the world’s transition to a future sustainable H2-based energy economy.

Sustainable Management of Urban Plastic Waste Through Circular Economic Approaches covers the technologies and methods essential to overcome single-use plastic processing waste. It describes the biotechnological methods, cutting-edge research, procedures, and applications required to safeguard global sustainable development along with plastic waste management. This book: • Describes technological advances made towards remediation and valorization technologies of plastic pollutants to reduce microplastic pollution. • Focuses on accelerating using single-use plastic waste in value-added products. • Includes examples and case studies of impact and treatment of plastics in the circular economy. • Explains the socio-economic benefits of reducing plastic pollution. This book will be of interest to researchers, scientists, and engineers working on sustainable management of plastic waste, especially in the chemical and environmental engineering and biotechnology sectors.