Application of synthetic biology for modification of Saccharomyces cerevisiae aiming to control bacterial contamination in the sugar and alcohol industry

Abstract

Biofuels are a central theme in the search for sustainable development. Brazil is the world's second-largest producer of first-generation ethanol and uses the yeast Saccharomyces cerevisiae to ferment mainly sugarcane must into ethanol. Given the enormous scale, the process is not sterile and considerable losses occur due to bacterial contamination. This contamination reduce fermentation performance and can cause interruption of the process to clean the structure. Estimates point to potential losses of more than 25% of production due to contamination. In order to control this contamination, antibiotics are used and, at the end of fermentation, the yeasts are treated with acids and reused. This process selects bacteria that are resistant to both antibiotics and the acidic pH and ethanol content within the vats. In addition to consuming nutrients from the raw material, these bacteria produce acids that harm the yeast's metabolism and reduce their viability. Despite these losses, the solutions on the market focus on improving yeast for production. Such alternatives do not focus on contamination and require recurring applications of the products, which makes production more expensive and can increase the emergence of bacteria resistance to the antibiotics used. In this project, we propose the construction of a bioengineered yeast strain capable of producing and secreting endolysins. These enzymes, produced by bacteriophages, attack the bacterial cell wall, reducing its resistance and leading to its rupture. The presence of this strain is expected to control contamination and persist throughout the fermentation cycles. If this prediction is confirmed, it will represent an important advance for the industry and will constitute a totally biological and continuous method of controlling contamination, without the need for external supplementation and will allow a reduction in the use of acids and antibiotics and an increase in ethanol production. To achieve this objective, we will use synthetic biology tools with standardization of DNA segments to facilitate cloning, as well as the creation of plasmids for these constructions. This platform may be expanded in the future to offer various solutions to the market in the areas of Bioeconomy, in the Industrial Biotechnology, Agribusiness and Food segments. (AU)