Isolation and Molecular Characterization of Biosurfactant-Producing Yeasts from Saps of Elaeis guineensis and Raphia africana

Aim: This study investigated the screening and molecular characterization of biosurfactant-producing yeasts from saps of Elaeis guineensis (oil palm) and Raphia Africana (Raphia palm).

Methodology: Physicochemical characteristics (pH, temperature, alcohol contents, and reducing sugars) of the saps of Elaeis guineensis and Raphia africana were determined. The capacity of the yeast isolates from both samples to produce biosurfactant was evaluated using emulsification index (E24), emulsification assay, haemolytic assay, oil displacement test, and tilted glass slide. The yeast isolates were identified based on their phenotypic, microscopic, biochemical, and molecular characteristics.

Results: Chemical analysis of the palm wine saps revealed respective pH, temperature, alcohol, and reducing sugars contents of 5.68, 17.1°C, 0.943% and 1.090 mg/mL for Elaeis guineensis and 5.26, 16.9°C, 0.884% and 2.099 mg/mL for Raphia africana. Six isolates (SA-2, SA-5, SB-3, SB-5, SB-6 and SB-8) out of sixteen isolates (16) distributed within both samples were found to produce biosurfactant. Phylogenetic analysis based on the internally transcribed spacer (ITS) genes classified the six isolates as Candida haemulonis SA2, Pichia kudriavzevii SA5, Pichia kudriavzevii SB3, Pichia kudriavzevii SB5, Pichia kudriavzevii SB6, and Pichia kudriavzevii SB8. The sequences obtained from the study have been deposited in GenBank under the accession numbers MN007219.1-MN007224.1. The result obtained from the study revealed high biosurfactant activity with a maximum E24 of 64.5% compared to E24 of 72% by sodium dodecyl sulphate (SDS).

Conclusion: The study demonstrated that saps from Elaeis guineensis and Raphia africana were suitable sources of biosurfactant-producing yeasts with high capacity for hydrocarbon emulsification. The main six biosurfactant-producing yeasts were found to belong to the genera Candida and Pichia.