Background/aim: Considerable attention has been given to the use of biosurfactants in recent times because of their potential industrial and environmental applications and ecological friendliness. Hydrocarbon-polluted soils have been major sources of biosurfactant-producing bacteria; resultantly, this study had been aimed at isolating and characterizing biosurfactant produced by Klebsiella pneumoniae strain IVN51 isolated from hydrocarbon-polluted soil in Ogoniland, Nigeria. Methodology:The biosurfactant screening techniques employed were emulsification assay, emulsification index (E 24 ), lipase activity, haemolytic assay, oil spreading, and tilted glass slide. The bacterial isolate was identified based on phenotypic, biochemical, and molecular means. Thin-layer chromatography (TLC) and gas chromatography mass spectrometry (GC-MS) analyses were used in the classification and characterization of the biosurfactant produced. The biosurfactant produced was applied on selected hydrocarbons to determine its emulsifying capacity. Results:The phylogenetic tree analysis of the 16S rRNA gene classified the isolate as K. pneumoniae strain IVN51. The sequence obtained from the isolate has been deposited in GenBank under the accession number KT254060.1. The result obtained from the study revealed high biosurfactant activity with a maximum E 24 of 60 % compared to E 24 of 70 % by sodium dodecyl sulphate (SDS). In addition, the biosurfactant showed emulsifying activity against the following hydrocarbons: petrol, kerosene, xylene, toluene, and diesel. The optimum cultural conditions (temperature, pH, carbon, nitrogen, hydrocarbon, inoculum concentration, and incubation time) for growth and biosurfactant production by K. pneumoniae IVN51 were determined. The biosurfactant was characterized as a phospholipid using TLC, while the GC-MS analysis identified the phospholipid as phosphatidylethanolamine. Conclusion:This study has demonstrated the capacity of K. pneumoniae strain IVN51 isolated from hydrocarbonpolluted soil to produce biosurfactant and the effectiveness of the produced biosurfactant in emulsifying different hydrocarbons. Furthermore, the biosurfactant produced was found to belong to the class, phospholipids based on the TLC and GC-MS analyses.

Aims:This study is aimed at determining the effect of cultural condition on biosurfactant production by Candida sp. isolates from saps of Elaeis guineensis. Methodology: Chemical analysis of the sap was carried out. Yeast isolates from the sap were screened for biosurfactant production based on emulsification index (E 24 ), emulsification assay, haemolytic assay, oil displacement test, CTAB and tilted glass slide ability. The best biosurfactantproducing yeast isolate was identified based on its phenotypic, microscopic, and biochemical characteristics. The emulsification capacity of the produced biosurfactant on selected oils was studied. Optimum cultural and nutritional requirements (temperature, pH, inoculum concentration, nitrogen sources and carbon sources) for biosurfactant production by the isolate were determined. Nwaguma et al.; BJI, 23(3): 1-14, 2019; Article no.BJI.50629 2 Results: The characteristics of the sap from Elaeis guineensis were reducing sugar (0.51 ± 0.03 mg/ml), alcohol (14.04 ± 0.15%), specific gravity (0.827±0.024), and pH (5.68±0.03). The crude biosurfactant produced displaced a thin film of crude oil on petri dish by 55 mm, and revealed high emulsification index (E 24 ) of 52.5% using Olive oil as substrate compared to E 24 of 60.6% by sodium dodecyl sulphate (SDS). Based on colonial, microscopic, and biochemical characteristics, the isolate SA2 was identified as Candida sp. The crude biosurfactant showed varying capacity in emulsifying the different oils that were examined. Optimization data revealed maximum biosurfactant production after 7 days of incubation, inoculum concentration of 10%, at temperature of 20ºC, pH of 2 with cassava peel as substrate. Original Research Article Conclusion:The study has demonstrated the capacity of Candida sp. from the sap of Elaeis guineensis to produce biosurfactant utilizing cassava peel as substrate. The use of cassava peel, which represents a low-cost substrate, is important in reducing the cost of biosurfactant production. Moreover, using yeasts from Elaeis guineensis make the production process ecologically friendly.

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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.