Molecular characterization and prospective economic value of yeasts isolated from different waste fruit peels

Aims: Adjustments in lifestyles have contributed to a gradual increase in the production and consumption of fruits worldwide, thus leading to the availability of fruit peels.This study was aimed to understand the load, types and industrial importance of yeasts in ten various fruit peels (pawpaw, pineapple, mango, banana, lime, lemon, watermelon, soursop, apple and African wild mango) from the Akure metropolis, Nigeria.Methodology and results: Yeast isolates were assessed for diversity after the D1/D2 domain of the 26S rDNA was sequenced to confirm their identities.Subsequently, isolates were probed for their ability to ferment glucose and sucrose (20% w/v) by using a Warburg manometer to determine the yield of CO2 compared to commercially available Baker's yeast.Ethanol yields were measured by the specific gravity method.Yeast loads were highest in pineapple (4.53 10 4 CFU/g) and mango peels (4.47 10 4 CFU/g) but least in watermelon peels (1.33 10 4 CFU/g).Thirty identified yeast isolates were representatives of Issatchenkia orientalis, Pichia fermentans, Pichia kudriavzevii, Lachancea fermentati, Candida albicans, Wickerhamomyces, Saccharomyces cerevisiae, Hanseniaspora uvarum and Pichia cecembensis.Among the most active sugar fermenters, Saccharomyces cerevisiae EXF-6472 peaked at 170 L CO2 in glucose and 180 L CO2 in sucrose, which were slightly higher when compared with 150 L CO2 from Baker's yeast.Ethanol yields were maximum in Pichia kudriavzevii C105 with values of 17% (v/v) and 5.8% (v/v) from glucose and sucrose, respectively.Conclusion, significance and impact of study: Fruit peels are a crucial reservoir for a variety of yeasts, which can be harnessed for cellular metabolites of crucial importance in bakery and brewery industries.