Comparative analysis of the kinetic growth parameters and ethanol production in non-Saccharomyces yeasts at the bioreactor level using Agave cupreata juice

The mezcal production in the state of Michoacán, located in central Mexico, is considered an informal activity with little to no regulation. The raw material is obtained from wild Agave populations, where dozens of species proliferate without any type of management. Consequently, the process is inefficient and the product obtained does not comply with the Mexican Mezcal Regulatory Council’s standards. Therefore, the object of this study was to analyze fermentation using a variety of yeast strains at the bioreactor level in order to establish statistical differences in the production of ethanol and biomass. Five yeasts (Kluyveromyces marxianus, Zygosaccharomyces bailli, Zygosaccharomyces rouxi, Pichia kluyveri and Isstchenkia terrícola) were added to YPD medium with Agave cupreata juice. Each yeast was inoculated for 18-24 hours, stirring at 180 rpm at a temperature of 28 ° C. In order to carry out the fermentation process, it was placed in a bioreactor for 60 hours at a temperature of 28 ° C, stirring at 150 rpm with an oxygen supply of 290 mL / min. This was done in triplicate. Throughout this process, samples were taken every four hours in order to measure biomass, ethanol production, acetic acid, reducing sugars, glucose, fructose, pH, and cell growth. In conclusion, of the yeasts analyzed P. kluyveri  had a significant ethanol production (41.67 g / L) and the shortest fermentation time (28 h) in addition to lower acetic acid production (0.17 g / L). The maximum biomass yield was 0.13 g / g, which indicates that it has great potential for the industrial production of ethanol using Agave cupreata juice.