Yeast Fuel, Developed by Chula’s Faculty of Science Soon to Expand Its Production for the Aerospace Industry

Researchers from Chulalongkorn University have made use of forage grass to feed microorganisms and convert the resulting fat into jet fuel. They aim to expand petroleum-based oil replacement production to reduce impacts on human health and the environment.

Yeast is a microorganism that is an important ingredient in many foods and beverages. However, in the future, yeast will play a major role in the production of fossil-based renewable fuels. 

Currently, researchers from Chulalongkorn University’s Faculty of Science are accelerating their technological development to scale up the production of aviation biofuel from yeast. This is an extension of the successful results of research that found a strain of yeast with a high potential for producing fat for use in aviation fuel. In addition to producing yeast oil, they use agricultural waste as food to grow microorganisms. This is another way to reduce burning problems and increase the value of agricultural waste. 

How did the research originate?  

Petroleum is an important source of fuel in today’s world, both in various industrial sectors and in transportation, especially the aircraft industry. 

 A report from the Department of Energy Business of the Ministry of Energy (2019) stated that Thailand’s jet fuel import volume has increased significantly. In 2016, Thailand imported 84.9 million liters of jet fuel, but only four years later, in 2019, the amount of jet fuel imports soared to 376.3 million liters per year. 

This increase in fuel imports reflects growing industrial demand and the need to find innovations to produce alternative energy that is more friendly to human health and the environment than petroleum. 

The team led by Prof. Dr. Warawut Chulalaksananukul and Asst. Prof. Dr. Chompunuch Glinwong from the Department of Botany, Faculty of Science, Chulalongkorn University has carried out the “Development of scaling-up technology for production of microbial lipid for biojet fuel synthesis” research project. 

According to Prof. Dr. Warawut, “The team has been successful in the separation of Saccharomyces cerevisiae yeast (CU-TPD4 strain) that has a high potential for fat accumulation. We have used yeast to produce biojet fuel to meet future energy demand. If we can develop Thailand’s potential in the production of bio-jet fuel, it would help our economy progress as well.”  

The project has received funding from the National Research Council of Thailand, focusing specifically on the Sino-Thai Plans for Renewable Energy to work on the extraction of fat, production of bio-jet fuel from microbial lipid synthesis, and bio-refinery of jet fuel from biomass resources. Aside from the two researchers mentioned, the team also includes three doctoral students from the Department of Botany, namely Dr. Nuttha Chuengcharoenpanich, Dr. Wannaporn Wattanasunthorn, and Mr. Thanapong Tangwanaphrai, with the collaboration of Dr. Surisa Suwannarangsee from the National Centre for Genetic Engineering and Biotechnology under the National Science and Technology Development Agency. They have collaborated with a group of Chinese researchers, including Prof. Zhongming Wang and Prof. Wei Qi from the Guangzhou Institute of Energy Conversion at the Chinese Academy of Science (GIEC). 

High-potency yeast produces fuel 

The researchers selected the yeast from 53 soil samples found in Mae Hongson and other nearby provinces and discovered Saccharomyces cerevisiae yeast (CU-TPD4 strain), which has a high potential for fat accumulation. This came at a time when there had not yet been any reports that this type of yeast could produce high levels of fuel at the same level as existing fuel-producing yeast. 

“S. cerevisiae is classified as a microorganism with high safety levels. It is known to have been used for a very long time, is Generally Recognized as Safe, GRAS, and is therefore used in the food production industry, such as for beer or bread production. Yet, it has not been reported that the particular strain of yeast has been used for the production of fat at the industrial level.”  

Prof. Dr. Warawut explained that the type of yeast that has been discovered can produce and collect fat in the cells at a level as high as 20–25% of the dry cell weight. These fat properties are extremely beneficial for the development of bioenergy, such as biodiesel.   

“Using oleaginous yeast as a feedstock for biofuel production has several advantages over using plants as an oil source, including the fact that the life cycle of yeast is short, a variety of foods can be used for its cultivation, it is relatively cheap, and it requires little labor. It can be cultivated at any time and doesn’t depend on the season; scaling up production is easy, while the fat produced has the same characteristics as that produced from plants. It is safe both for humans and the environment. 

Prof. Dr. Warawut also added an important advantage of oil production from yeast, saying that “when the process is developed and the yeast is used at the industrial level, its culture at 40 degrees Celsius can help reduce the cost of the cooling process to control the temperature of the fermentation tank.” 

This research has attracted interest both nationally and internationally from researchers from such institutions as Hamburg University of Technology (TUHH) in Germany and Toulouse Biotechnology Institute (TBI) in France. Researchers from Hamburg University of Technology (TUHH) in Germany and Toulouse Biotechnology Institute (TBI) in France saw the opportunity to expand the CU-TPD4 yeast leavening production for use in oil, bread, alcohol, and other food products. 

Raising yeast using agricultural waste 

In addition to getting energy that is cleaner than fossil energy, the process of growing yeast to produce oil also makes use of agricultural waste, which is part of driving the circular economy and reducing air pollution problems from the burning of agricultural waste. 

“In addition to animal fodder grass, agricultural waste and various types of lignocellulosic biomass can be used as carbon sources to feed fat-accumulating yeasts for example, rice straw, corn cobs, sugarcane bagasse, as well as various vegetable and fruit peels such as banana peels, durian peels, and bean shells, especially rice straw, which is a large amount of waste material in Thailand. Therefore, it is considered another way to use agricultural waste to be beneficial as well.” 

Moreover, there are also reports of waste disposal such as office paper scraps. and wastewater from industrial plants, including wastewater from paper factories. Wastewater from a sago flour factory and wastewater from homes can be used as a carbon source as well. The main aim is to reduce production costs, eliminate waste, and increase the value of such waste materials to make them more useful. 

Improvement of yeast strains, expansion of oil production, and adding value to the food and pharmaceutical industries 

The growth of yeast and the amount of oil produced by yeast on a laboratory scale are still not sufficient to meet the demand for fuel in the market. Therefore, it is necessary to develop technology to expand production capacity. 

“This can be done by using different methods, such as improving strains of fat-accumulating yeast to increase their ability to produce and accumulate more fat or improving the yeast to be more resistant to conditions that are not suitable for growth. Improve yeast to be more resistant to conditions that are not suitable for growth, such as being able to withstand higher temperatures in the production process to reduce cooling costs. They can also be more resistant to toxins that occur from the process of pretreatment of agricultural waste to reduce the steps and costs of the detoxification process, for example.” 

Prof. Dr. Warawut explained that at present, the research is focused on increasing the oil production level of the yeast S. cerevisiae at higher levels by genetically modifying the increased expression of the enzyme Acetyl-CoA carboxylase in the TWP02 strain, resulting in increased fat production. 

After that, researchers scaled up their study of the oil production process from yeast cells using research tools from the Biological Engineering and Precision Fermentation Laboratory (Bioengineering and precision fermentation laboratory) of the Biotechnology and Materials Research Department Innovation Institute, PTT Public Company Limited, which is Thailand’s leading laboratory in biological processes and fermentation processes. Biotechnology research tools from the upstream process are available for the selection and improvement of microbial strains. The fermentation process ranges from a laboratory scale with a 2-liter fermentation tank to a prototype research unit with a 20,000-liter fermentation tank. This includes downstream processes used to separate microbial cells, such as breaking microbial cells with pressure, increasing the concentration and purity of biologics, and forming biopharmaceuticals into dry form by heating or cooling. The potential of the laboratory helps enable this research project to evaluate the potential for designing an appropriate biofuel production process for aircraft. 

Prof. Dr. Warawut ended by saying that in addition to producing biodiesel and jet fuel, improving fat-accumulating yeast strains can produce fatty acids such as unsaturated fatty acids. This is a type of fat that is in demand in the market and has a high value. It can also be used as a starting material for producing other products in the fields of food, cosmetics, and medicine that can meet the needs of sustainable life science businesses as well. 

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