The biological agent is an active beginning in biotechnological processes and one of its most important elements. The range of biological agents is constantly expanding. The main ones include microorganisms, microbial associations, enzymes, fungi, and plants. Until now, the most important place is occupied by a traditional object—a microbial cell. It should be noted that environmental biotechnology is a low-waste technology with environmentally friendly technical implementation. They aim to clean the environment from various pollutants and produce environmentally friendly products with the possibility of recycling secondary resource flows. Therefore, the choice of biological agent here has a conceptual basis associated with the need for in-depth knowledge of physiology and biochemical processes of growth and metabolism of biological objects and the need for their sanitary and hygienic assessment.