Gas chromatography-mass spectrometry characterization of carotenoids produced by yeasts isolated from edible fruits and vegetables marketed in Osogbo metropolis, Southwest Nigeria

Abstract

Globally, there is a rising demand for the replacement of chemically synthesized carotenoids (which dominate the market and negatively impact the environment and public health) with organic carotenoids. Therefore, we produced and characterized carotenoids from yeasts isolated from edible fruits and vegetables from three local markets in Osogbo, Nigeria. Five samples each of fresh edible fruits (orange, banana, pineapple, watermelon, and mango) and vegetables (carrot, cucumber, lettuce, green pepper, and tomato) were collected from Shasha, Testing Ground, and Oke-Baale markets. Yeasts were isolated on plate count agar (PCA) and presumptively identified using standard methods. Pigmented colonies were carefully picked, purified, and presumptively identified. Mass cultivation of pure culture was done on plate count agar, and extraction was done using chloroform after cell hydrolysis. The extracts were characterized using gas chromatography-mass spectrometry (GC–MS), and the yeast isolates' identity was confirmed using molecular methods. A total of 24 yeasts were obtained from the fruit and vegetable samples. Four pigmented yeasts, Rhodotorula mucilaginosa (LETA) and (LETB), Rhodotorula toruloides (GP-1), and Candida haemulonis (GPS-1) were obtained from lettuce and green pepper samples, respectively. The GC–MS analysis revealed the presence of 35 compounds in pigments from LETA and LETB, 20 compounds from GP-1, and 33 compounds from GPS-1. The molecular ion (m/z) values 441 m/z, 398 m/z, 486 m/z and 337 m/z recorded in pigment LETA, LETB, GP-1, and GPS-1 suggest the presence of β-carotene, lycopene, lutein, and phytoene, respectively. The identity of the yeasts was confirmed, and accession numbers PPO78657.1, PPO78678.1, PPO78659.1, and PPO78660.1 were assigned correspondingly. This study unveiled the pigmented yeasts from lettuce and green pepper samples as a viable alternative source of carotenoids. Further studies on the purification and application of carotenoids are recommended.