Genetically modified yeast permits conversion of agave to ethanol

A GM strain of brewer’s yeast Saccharomyces cerevisiae developed by Brazilian researchers could significantly grow the production of ethanol biofuel. A patent application has been filed with Brazil’s patent office.

By Julia Moióli  |  Agência FAPESP – Researchers at the State University of Campinas (UNICAMP) in Brazil have developed a genetically modified strain of the brewer’s yeast Saccharomyces cerevisiae that digests the main carbohydrate in agave, a succulent common in Mexico and in Brazil’s Northeast region.

With this innovation, the plant has the potential to become one of the most important raw materials for the production of ethanol, a key biofuel in the context of climate change, in semi-arid environments. A patent application has been filed with the National Institute of Intellectual Property (INPI), Brazil’s patent office (BR 10 2024 009105 1).

Agave is well-known as the plant from which the distilled spirit tequila is made and has more recently become a popular sweetener. In Brazil it is grown only for sisal and most of its biomass is thrown away.

According to the researchers, the main reason this biomass is not yet used to produce ethanol is lack of efficient conversion of the plant’s sugars, especially inulin, a fructose polymer whose digestion requires an enzyme not naturally found in S. cerevisiae, the yeast used in ethanol production.

Before agave can be fermented to make tequila, for example, the inulin and other carbohydrates must be broken down by hydrolysis into simpler sugars that can be digested by the yeast. Alternatively, other fungi that naturally consume the inulin could be used, but so far none has been found with the efficiency required for industrial processing.

Researchers working at the Genomics and Bioenergy Laboratory in UNICAMP’s Institute of Biology (LGE-IB) used genetic engineering to create a novel strain of S. cerevisiae that can ferment agave for the purpose of ethanol production.

“There’s a pathogenic fungus that feeds on agave via a specific enzyme,” said Ana Clara Penteado David, a researcher at LGE-IB and author of the master’s project that gave rise to the genetically modified yeast. “We added the enzyme to S. cerevisiae and showed in laboratory trials that it was capable of converting agave inulin to ethanol.”

“Thanks to this innovation, agave now has the potential to increase the use of ethanol in normal cars and hybrid electric vehicles with batteries and ethanol-fueled engines, as well as its use as sustainable aviation fuel,” said Fellipe da Silveira Bezerra de Mello, a researcher and professor at LGE-IB and one of the coordinators of the project. “Brazil’s position as a global leader in the sector with a long history of developing biofuel technology will also boost this advantage.”

Besides the biofuel application, the researchers also expect the patent to be of interest to the food industry, which uses inulin in fructose and syrup products.

Brazilian Agave Development Program

The genetically engineered S. cerevisiae strain is part of the Brazilian Agave Development Program (known by the acronym Brave), a partnership involving UNICAMP, Shell, and higher education and research institutions such as Senai Cimatec, the Federal University of Recôncavo da Bahia (UFRB), the University of São Paulo (USP) and São Paulo State University (UNESP). According to Gonçalo Pereira, full professor at IB-UNICAMP and co-coordinator of the project, the purpose of the Brave program is to make agave the “sugarcane of the sertão” in terms of productivity. The sertão is the drought-ridden hinterland of Brazil’s Northeast region.

“There are more semi-arid areas than forests in the world but, curiously, specific technologies for this type of vegetation have never really been developed,” Pereira said. “We want to focus on doing so, making production of agave viable in the sertão, which covers 105 million hectares [a sizable proportion of Brazil’s total area, which is 850 million hectares]. With 10 million hectares, the amount of ethanol Brazil produces could be doubled.

“It’s important to note that the plant is perfectly adapted to this environment, especially thanks to its stomata [small mouthlike structures on the surface of leaves and stems], which perform photosynthesis, capturing carbon gas at night, when the temperature is lower, and converting into an acid. During the day, the stomata stay closed in order not to lose water.”

Although a fundamental first step has been taken in this direction, obstacles remain, such as eliminating substances that are toxic to the yeast from agave juice.