ABSTRACT
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 (E24), emulsification assay, haemolytic assay, oil displacement test, CTAB and tilted glass slide ability. The best biosurfactant-producing 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. 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 (E24) of 52.5% using Olive oil as substrate compared to E24 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. 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.
ABSTRACT
Aim: To study multiple antimicrobial resistances in Vibrio spp. isolated from river and aquaculture water sources in Imo State Nigeria. Methodology: A total of 157 Vibrio isolates from river and aquaculture water sources were analysed for multiple antimicrobial resistance during a 6 month period. Antimicrobial resistance profile was determined by the Kirby-Bauer technique, while the phenotypic expression of β-lactamase production was performed by the double disk diffusion method. PCR was used to screen isolates for the presence of β-lactamase resistance genes. Results: The isolates from river water expressed high resistance rates (81.3 to 97.8%) to the following antimicrobials: mezlocillin, doxycycline, tetracycline, carbenicillin and ampicillin, while resistance rate to kanamycin was moderate at 40.9%. Resistance rates for the aquaculture water Isolates were also high for the same antibiotics as the river water isolates, while resistance rate to kanamycin was low to moderate at 32.8%. Phenotypic screening of isolates for ESβL production showed the isolates were resistant to β-lactam antimicrobials and the β-lactamase inhibitor of amoxicillin/clavulnic acid combination. Gel electrophoresis of PCR products showed amplification for blaTEM of size 964bp. Conclusion: Results showed the presence of highly resistant Vibrio isolates from the sampled environmental sources. The presence of resistance markers among the isolates in this study infers that they could be agents of transfer of resistance to other bacterial pathogens found in river and aquaculture water.