Assessment of biosurfactant as an emulsifier produced from Bacillus aryabhattai SPS1001 grown on industrial waste coal tar for recovery of bitumen from oil sands

Bacillus aryabhattai SPS1001 grown using a nutrient broth medium supplemented with waste coal tar results in a maximum yield of biosurfactant (0.43 g L-1) and surface tension reduction to 36.55 +/- 0.02 mN/m at 48 h whereas emulsification index (E-24) with engine oil and mineral oil was measured 88.53% and 89.21%. Emulsion forming and stabilizing efficiency of biosurfactant was retained during exposure to a temperature range (20-121 degrees C), and salt (NaCl) concentrations up to 12% whereas in the case of pH 6.5 and 7 activity of the biosurfactant dropped significantly and no emulsion formed above pH 11. Quantitative relation of emulsion stability at biosurfactant concentration 0.18 g L-1 was studied in lowering the interfacial tension of engine (2.13 +/- 0.9 mN/m) and mineral (3.61 +/- 1.9 mN/m) oil at the interface which limits recoalescence of droplets due to Gibbs-Marangoni effect. Zeta potential of the engine and mineral oil emulsions recorded - 23.5 and - 25.5 mV respectively and the polydispersity index (PDI) was measured 0.49 and 1.0 respectively which shows a monodisperse sample indicating the stability of emulsion against droplets coalescence. Structural characterization of biosurfactant by FT-IR reveals strong, broad O-H stretching in alcohol and C-O stretching vibration in primary alcohol respectively and reveals glycolipid nature. Cell-free supernatant containing biosurfactant concentration (0.43 g L-1) was used to recover the bitumen (59%) from oil sands at 70 degrees C, and the addition of NaCl solution (0.5%) increased the bitumen yield to 63% by decreasing interfacial tension to 0.1 mN/m. Hence, the glycolipid biosurfactant with high and long-term thermostability finds its suitability for biosurfactant-mediated bitumen recovery from oil sand and offers new insight into potential applications in sustainable environmental technologies.

Automated summary

Bacillus aryabhattai SPS1001 grown in a nutrient broth medium supplemented with waste coal tar demonstrated high production of biosurfactant with excellent emulsification and stabilization properties, making it suitable for applications such as bitumen recovery from oil sands.