Production and Optimization of Biosurfactants from Citrullus lanatus Seeds and Activity Determination with Pseudomonas aeruginosa Isolate
T. O. Ukwueze
Department of Biochemistry, University of Nigeria, Nsukka, Nigeria.
V. E. O. Ozougwu
Department of Biochemistry, University of Nigeria, Nsukka, Nigeria.
O. U. Njoku
Department of Biochemistry, University of Nigeria, Nsukka, Nigeria.
G. S. Haruna *
Department of Biochemistry and Molecular Biology, Nasarawa State University, Keffi, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Aims: To produce and optimize biosurfactants from Citrullus lanatus seeds.
Study Design: Randomized design.
Place and Duration of Study: Department of Biochemistry Lab. and Department of Microbiology lab. University of Nigeria, Nsukka, between April and August, 2017.
Methodology: Biosurfactants were produced in two fermentation media consisting of basal mineral medium+ watermelon (C. lanatus) seed (BMM+WMS), and Nutrient broth (NB). Optimization of production process was carried out with respect to time/duration of fermentation and pH of production which indicated 7 days fermentation period at pH 8.0. The Pseudomonas aeruginosa used was isolated from soil. The biosurfactants stability under some environmental conditions were studied using; Thermostability test at 30°C, 60°C, and 100°C; Halostability test with %w/v concentration of NaCl in; 2%NaCl, 5%NaCl, 7%NaCl, and 10%NaCl; pH stability test was conducted with pH 2.0, pH 4.0, pH 6.0, pH 8.0, pH 10.0, and pH 12.0.
Results: Proximate analysis(%) showed; protein (0.317 ± 0.02), lipid (17.66 ± 0.17), carbohydrate (62.77 ± 0.21), ash (2.33 ± 0.24), fibre (4.84 ± 0.79), and moisture (12.06 ± 0.17).The Emulsification index (E24) for the crude biosurfactant solutions (supernatants) that resulted from the two production media, and sodium dodecyl sulfate 1% SDS in distilled water (control) using palm oil (PO), olive oil (OO), engine oil (EO), kerosene (KR), and petrol (PT) for BMM+WMS biosurfactant gave PO (79.66±1.52%), OO (64.66±7.23%), EO (15.33±4.93%), KR (12.66±6.50%), and PT (0.00±0.00%). Also, the NB biosurfactant resulted in; PO (71.00±2.00), OO (54.33±3.78), EO (42.66±6.42), KR (22.66±7.57), and PT (0.00 ± 0.00) E24 values. There were significant decreases (p<0.05) in biosurfactants activities in all vegetable oils and hydrocarbons when compared to the SDS surfactant. However, there was no significant decrease (p>0.05) in WMS biosurfactant activity in palm oil compared to SDS surfactant activity in palm oil.
Conclusion: The biosurfactants were shown to have high thermostablity as their E24 values increased with rise in temperature.
Keywords: Bioemulsifiers, optimum, thermostability, halostability, microorganism.