New Progress in Ethanol Production from Lignocellulose

Fuel ethanol, as a high-quality and renewable clean energy source, is widely used internationally. When added to gasoline fuel, it can replace some petroleum-based fuels and reduce pollutant emissions. Currently, fuel ethanol is mainly produced by fermenting starch from grains and plant sugars. Utilizing various types of lignocellulosic materials such as widely available agricultural and forestry wastes as raw materials for the production of fuel ethanol has an extremely broad prospect and is also a focus of research in the field of biotechnology for decades. Producing ethanol from lignocellulose requires at least three steps: pre-treatment, enzymatic hydrolysis, and fermentation. During the pre-treatment process, toxic substances produced severely inhibit yeast growth and ethanol fermentation, becoming the main technical bottleneck in the production of cellulose ethanol. Currently, to achieve better fermentation results, deep detoxification of pre-treated lignocellulose and its enzymatic hydrolysate is carried out through methods such as washing, physical, chemical, and biological. However, the complex process, expensive equipment investment, large water consumption, and loss of fermentable sugars greatly reduce the economic benefits of cellulose ethanol production, thereby restricting the industrialization process of cellulose ethanol.         The research team led by Zhang Zongchao from the Biomass Conversion Technology Research Group of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, in their research on the production of ethanol from lignocellulose, discovered that polyethylene glycol has excellent biological compatibility with yeast cells, and that polyethylene glycol has a significant protective function for industrial brewing yeast cells, known as "in situ detoxification". The external protection of this chemical molecule enables yeast cells to maintain their ability to ferment and produce ethanol from the hydrolyzed liquid of lignocellulose, even when they are exposed to toxic substances. The research results show that industrial brewing yeast can directly convert lignocellulose hydrolyzate into ethanol under the protection of polyethylene glycol, without the need for genetic modification or adaptive cultivation. This method can effectively simplify the production process, reduce water consumption and equipment investment, and promote the industrialization process of cellulosic ethanol.