Identification and Characterization of High Efficacy Thermotolerant Yeast for Bioethanol Production from Fruit Waste

To explore high efficacy native stress tolerant yeast strain for better ethanol yield as compared to Saccharomyces cerevisiae, five isolates were selected by plate assay using acidic cerric ammonium nitrate and quantified spectrophotometrically for ethanol production. The yeast cultures varied in their ethanogenic capabilities. The isolate BGY1 showing better in vitro ethanol production (7.1 g/l) in YPD broth in 48 h as compared to S. cerevisiae and other strains was found superior. All the five cultures were tested for their alcohol producing efficacies using diluted unprocessed whole fruit pulp of inferior quality under liquid state fermentation (LSF) conditions. Batch fermentation with native yeast isolate BGY1 resulted in higher ethanol yield (38.7 g/l) as compared to that with S. cerevisae (20.1 g/l) in 48h. Ability to grow in YPD broth at higher temperature (44°C) indicated better thermo tolerance of the isolate BGY1 as compared to S. cerevisiae and other cultures. The isolate BGY1, comprising of elongated cells with pseudohyphal structures as revealed by phase contrast microscopy and SEM was identified as PichiaKudriavzevii BGY1 based on 5.8 S ITS rRNA gene sequence analysis.