Microbial Fermentation Pathway for Clean Energy Production

Dear Colleagues,

Clean energy refers to primary energy sources with zero or low emissions of environmental pollutants and greenhouse gases，such as carbon dioxide, and mainly includes natural gas, nuclear power, geothermal energy, hydropower and other new and renewable energy sources. The widespread use of fossil fuels such as coal and oil over a long period of time has caused serious pollution to the global environment and even posed a threat to human survival. At the same time, fossil fuels are non-renewable energy sources and will be depleted with over-exploitation. Humankind is facing a serious test and challenges of resource exhaustion and environment pollution; therefore, the development of clean energy and sustainable economic and social development has become the mainstream and hot spot research topic in the world today. With the development of biotechnology and molecular biology, microorganisms are playing an increasingly important role in the production of clean energy. In addition, it has attracted great interest and attention. Specifically, the application of microorganisms to produce clean energy is mainly reflected in the following aspects.

1.1 Applications in clean coal research

Most coal contains high levels of inorganic or organic sulphur components. The direct use of coal has caused serious environmental pollution as the sulphur dioxide from coal combustion directly enters the atmosphere and promotes the formation of acid rain. Thermophilic acidophilic bacteria can be used to remove inorganic sulphur from coal, as well as organic sulphur, thus having a high economic value and social benefit. It is of great importance to environmental protection.

1.2 Application in ethanol research

At present, countries around the world are developing the use of ethanol biomass fuel. The production of alcohol by high-temperature fermentation through thermophilic bacteria can achieve the synchronization of fermentation and distillation with short fermentation cycles. Organic waste from industrial and agricultural production, such as straw and waste residues, is fermented under high temperature, acid and alkali conditions to produce ethanol or methane using mixed microbial flora. It can achieve an organic combination of environmental remediation and renewable energy.

1.3 Application in biodiesel and biogas research

Biodiesel has excellent properties such as environmental protection, and is renewable and biodegradable. Biodiesel is the second bioenergy product after ethanol that is expected to be promoted on a large scale, and is favoured by all sectors at home and abroad. The enzyme-catalyzed synthesis of biodiesel is carried out using lipase of microbial origin as the catalyst. This method has the advantages of mild reaction conditions, low energy consumption and low pollutant emissions. Microbial biogas production is a complex process in which five types of microorganisms, namely fermentative bacteria, hydrogen-producing acetic acid-producing bacteria, hydrogen-consuming acetic acid-producing bacteria, hydrogen-eating methanogenic bacteria and acetic acid-eating methanogenic bacteria, are used. These microorganisms work together to break down organic matter to produce methane and carbon dioxide. Microorganisms play an important role as the main body of biogas fermentation.

1.4 Applications in hydrogen research

Microbial hydrogen production is a type of bioengineering technology that uses microbial metabolic processes to produce hydrogen. It overcomes the disadvantages of industrial hydrogen production, such as high energy consumption and heavy pollution, and is a truly clean energy source due to its renewable and zero-emission advantages. Solar energy can be converted into hydrogen using photosynthetic bacteria or microalgae. Hydrogen can also be produced by fermenting bacteria. It can also be a combination of the two, i.e., using both photosynthetic and fermentative bacteria to produce hydrogen from complex substrates. The selection of bacteria with excellent hydrogen production performance and suitability for engineering is of great importance for the industrial bio-hydrogen production technology.

1.5 Applications in fuel cell research

Microbial fuel cells (MFCs) are ideal devices for converting chemical energy stored in organic matter directly into electrical energy using electricity-producing microorganisms as anode catalysts. Compared to the current organic matter power generation and wastewater treatment technologies, MFCs have the advantages of being clean and environmentally friendly in terms of operation and functionality, a high energy conversion rate, very fast recharge, low sludge production, a simple gas treatment process and avoiding the use of aeration devices. At present, MFCs research is still at an accumulative stage and the knowledge and information gained are still quite limited, so a significant amount of research and technological breakthroughs are needed to promote its application in practical wastewater treatment.

1.6 Application in carbon sequestration and new energy material production

CO₂, as the most important greenhouse gas, has exacerbated the greenhouse effect and caused a series of environmental problems. It is not only to save energy and reduce emissions, but also to achieve its rapid absorption and fixation. Microbial carbon sequestration and production of new material energy means that microorganisms use light energy and CO₂ to produce new material energy such as advanced unsaturated alkanes, oils and fats from cellular substances. It has a bright future and value as a solution to the difficulty of greenhouse gase fixation and as a type of environmental protection.

With the worldwide increasing demand for energy and environmental protection, the promotion and application of clean energy has become an inevitable trend. The unique advantage of microorganisms in clean energy production is that they are green and renewable resources, so they are attracting significant attention and are bound to be rapidly developed.

Dr. Li Feng
Guest Editor

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• clean energy
• microorganisms
• green and renewable energy
• enzyme catalysis
• biomass energy
• energy conversion