US scientists use evolutionary strategies to increase biofuel production efficiency

The production of biofuels from agricultural and forestry wastes such as straw can serve two purposes, but production efficiency still needs to be improved. Scientists resorted to the rules of evolution of nature, allowing bacteria to become more proficient in the decomposition of xylose in the survival competition, thereby improving the efficiency of biofuel production.

The Arizona State University issued a press communique a few days ago that a research team at the university has allowed E. coli to live in a special environment, forcing them to ferment and break down xylose to survive. After more than 150 generations of breeding, gene mutations increase the efficiency of these bacteria to break down xylose. After the mutant gene was transplanted to the strain used for fermentation, the decomposition efficiency increased significantly.

Xylose is a sugar containing 5 carbon atoms and is widely present in plants. Straw, rice hulls, sawdust, and subtilis all contain large amounts of xylose. Using these raw materials to produce biofuels can avoid the problems of using corn and sugar cane as raw materials to affect food production, and also eliminate agricultural waste. However, E. coli used for fermentation in industry will preferentially use glucose. As long as glucose is present in the environment, they will shut down the function of breaking down xylose.

Plant raw materials are usually also rich in glucose, so the power and efficiency of bacteria to break down xylose is insufficient. The research team placed E. coli in a medium containing only xylose. Bacteria that are not good at breaking down xylose will lose in the survival competition. The bacteria grew very slowly at first, but after more than 150 generations of evolution, they adapted to the new environment and thrived.

The analysis showed that the three groups of E. coli cultured in this way have undergone different transformations for the same batch of genes and they have all achieved success. One of the most eye-catching transformations involves a regulatory protein called XlyR. The mere adjustment of two amino acid switches will enable bacteria to efficiently break down xylose and inhibit the use of glucose. The researchers transplanted the mutant gene into industrial E. coli and, after four days of fermentation, the increase in production reached a maximum of 50%.

The researchers said that this discovery has broken through a major bottleneck in the field of biofuel production. They hope to cooperate with industrial agencies to conduct large-scale application tests to verify economic feasibility.