Evaluation of the antibacterial potential of plant extracts for control of contaminant Lactobacillus fermentum in the production of fuel ethanol

• Grant number: 19/24098-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2020
• End date: February 28, 2021
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Pedro de Oliva Neto
• Grantee: Ana Laura Silvério dos Santos
• Host Institution: Faculdade de Ciências e Letras (FCL-ASSIS). Universidade Estadual Paulista (UNESP). Campus de Assis. Assis , SP, Brazil

Abstract

The fuel ethanol production process in Brazil is made from the fermentation of sugarcane molasses, but this process is not aseptic and suffers contamination caused by bacteria, especially Lactobacillus fermentum, responsible for reducing the fermentative efficiency performed by Saccharomyces cerevisiae yeast and increase the cost of the inputs. This occurs by nutrient competition, with consequent cellular flocculation, gum and acid production. In distilleries antibiotics and biocides are used in order to inhibit bacterial proliferation, but end up generating resistant bacteria, increasing the cost of the process, besides the chemical contamination of the yeast which also hinders its commercialization in the form of yeast flour. To change this scenario, the present study consists of testing new natural source antimicrobials, possibly present in vegetal extracts of the plants A. americana, A. classiflora, E. urograndis, P. venusta, S. saponaria L, S. campanulata, and T. procumbens L. The microorganisms used in this work will be L. fermentum ATCC 9338 and S. cerevisiae M-26. Initially, inhibition tests will be performed in test tubes to determine the Minimum Inhibitory Concentration (MIC) of the bacteria through the plant extracts. The extracts with antibacterial potential and without antifungal action will be used for extraction by organic solvents in order to potentiate the action and again will be evaluated for MIC. Those with the lowest concentrations will be used for alcoholic fermentation tests, simulating the industrial operation in batch fed with mixed cultures of S.cerevisiae and L. fermentum. Microbial growth, cell viability, acidity and alcohol yield will be evaluated. (AU)