As an expert in the field of environmental microbiology, I can provide you with a comprehensive understanding of the bacteria used in anaerobic digestion. Anaerobic digestion is a complex biological process where organic matter is broken down by microorganisms in an oxygen-free environment. This process is widely used for waste treatment and energy recovery, as it converts organic waste into biogas, which is a mixture of methane and carbon dioxide.

The process of anaerobic digestion involves a series of stages, each carried out by a different group of microorganisms. The main groups of bacteria involved in anaerobic digestion include:


1. Hydrolytic Bacteria: These bacteria are responsible for the initial breakdown of complex organic matter into simpler compounds. They secrete enzymes that hydrolyze proteins, carbohydrates, and fats into amino acids, sugars, and fatty acids.


2. Fermentative (or Acidogenic) Bacteria: Once the complex organics are broken down into simpler compounds, fermentative bacteria convert these into volatile fatty acids (VFAs), primarily acetic, propionic, and butyric acids, along with hydrogen and carbon dioxide.


3. Acetogenic Bacteria: These bacteria play a crucial role in the process by converting VFAs such as propionate and butyrate into acetic acid, hydrogen, and carbon dioxide. This step is essential as it prepares the substrate for the methanogenic archaea.


4. Methanogenic Archaea (Methanogens): The final step in anaerobic digestion is carried out by methanogens, which are archaea, not bacteria. They convert acetic acid into methane and carbon dioxide. There are two types of methanogens: acetoclastic methanogens, which convert acetate to methane and carbon dioxide, and hydrogenotrophic methanogens, which use hydrogen and carbon dioxide to produce methane.

It's important to note that while the term "bacteria" is often used colloquially to refer to all microorganisms, in the strictest sense, methanogens are archaea, a separate domain of life distinct from bacteria. They have different cellular structures and genetic material organization.

The efficiency of anaerobic digestion can be influenced by various factors, including temperature, pH, substrate composition, and the presence of inhibitors. Optimal conditions are necessary for the microorganisms to thrive and carry out their respective roles effectively.

In summary, anaerobic digestion is a multi-step process involving several types of microorganisms, with bacteria playing key roles in the hydrolysis, acidogenesis, and acetogenesis stages. The process is essential for waste management and renewable energy production, and understanding the role of each microorganism is crucial for optimizing the efficiency of anaerobic digesters.

read more >>

Many microorganisms affect anaerobic digestion, including acetic acid-forming bacteria (acetogens) and methane-forming archaea (methanogens). These organisms promote a number of chemical processes in converting the biomass to biogas. Gaseous oxygen is excluded from the reactions by physical containment.read more >>