Brazilian researchers used genetic engineering to develop a low-cost platform for the production of enzymes that break down sugarcane trash and bagasse for conversion into biofuel. The novel molecules have many potential industrial applications.
Researchers at the Brazilian Center for Research in Energy and Materials (CNPEM) have genetically engineered a fungus to produce a cocktail of enzymes that break down the carbohydrates in biomass, such as sugarcane trash (tops and leaves) and bagasse, into fermentable sugar for industrially efficient conversion into biofuel.
The development of low-cost enzyme cocktails is one of the main challenges in producing second-generation ethanol.
Second-generation biofuels are manufactured from various kinds of nonfood biomass, including agricultural residues, wood chips, and waste cooking oil. The CNPEM research group’s process paves the way for optimized use of sugarcane residues to produce biofuels.
The fungus Trichoderma reesei is one of the most prolific producers of plant cell wall-degrading enzymes and is widely used in the biotechnology industry. To enhance its productivity as a biofactory for the enzyme cocktail in question, the researchers introduced six genetic modifications into RUT-C30, a publicly available strain of the fungus. They patented the process and reported it in an article published in the journal Biotechnology for Biofuels.
“The fungus was rationally modified to maximize production of these enzymes of biotechnological interest. Using the CRISPR/Cas9 gene-editing technique, we modified transcription factors to regulate the expression of genes associated with the enzymes, deleted proteases that caused problems with the stability of the enzyme cocktail, and added important enzymes the fungus lacks in nature. As a result, we were able to allow the fungus produce a large amount of enzymes from agroindustrial waste, a cheap and abundant feedstock in Brazil,” Mario T. Murakami, Scientific Director of CNPEM’s Biorenewables Laboratory (LNBR), told Agência FAPESP.
Some 633 million tons of cane are processed per harvest in Brazil, annually generating 70 million metric tons of cane trash (dry mass), according to the National Food Supply Company (CONAB). This waste is underutilized for fuel ethanol production.
Murakami stressed that practically all the enzymes used in Brazil to decompose biomass are imported from a few foreign producers that keep the technology under trade secret protection. In this context, the imported enzyme cocktail can represent as much as 50% of a biofuel’s production cost.
“Under the traditional paradigm, decades of studies were needed to develop a competitive enzyme cocktail production platform,” he said. “Moreover, the cocktails couldn’t be obtain