Assessment of the Wettability of Hydrophobic Solid Substrate by Biosurfactant Produced by Bacillus aryabhattai SPS1001

Kinetics and Production of Rhamnolipid from Pseudomonas sp. TMB2 in Shake-Flask and Fabricated Batch Reactor

Rhamnolipid producing Pseudomonas sp. TMB2 was selected for this investigation to optimize the metabolite production in fabricated batch reactor after studying yield kinetics in shake-flask and tried to reduce the overall production cost through In-situ recovery technology. Using various kinetic models, maximum specific growth rate (μmax) and half velocity constant (KS) of TMB2 were determined to be 0.185 ± 0.0025 h-1 and 0.124 ± 0.024 g/L in shake-flask, respectively. Further, a batch reactor was designed with integration of a foam fractionate column in the lid of the vessel and their performances were compared with shake-flask studies. The yields of rhamnolipids production on biomass (YP/X), rhamnolipids production on substrate (YP/S) and biomass production on substrate (YX/S) were found to be higher in reactor than that of shake-flask. The best conditions for maximum rhamnolipid production in reactor were observed to be 2 vvm and 300 rpm, giving YP/S = 0.152 g/g, YP/X = 0.542 g/g and YX/S = 0.280 g/g. Rhamnolipid production was increased by ≈ 10.18% in the reactor than that of shake-flask in optimized conditions. Rhamnolipid concentrations in the foamate were also found to be higher than that of reactor vessels. Further, the performance of foam fractionation was validated through enrichment and recovery, which were found in the range of 2.75-4.86 and 25.33-64.64%, respectively.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-022-01021-0.

Assessment of Rheological Behaviour of Water-in-Oil Emulsions Mediated by Glycolipid Biosurfactant Produced by Bacillus megaterium SPSW1001

A screening programme using mineral salt medium supplemented with n-hexadecane resulted in isolating a Bacillus megaterium SPSW1001 which was capable of producing surface active molecules lowering culture medium surface tension to 27.43 ± 0.029 mN/m and interfacial tension to 0.38 ± 0.03 mN/m at 72 h and an emulsification index (E₂₄) (85.63%). The biosurfactant product was further used to assess its effects on the rheological characteristics of water-in-oil emulsion prepared with engine oil. Structural characterization of the biosurfactant product by FTIR revealed a C-O-C stretch in sugar moiety and ester carbonyl linkage group between sugar and fatty acids, respectively, while mass spectral analysis revealed its glycolipid nature, with an m/z value of 662.44. The fluid behaviour of water-in-oil emulsion showed a non-Newtonian viscoelastic dilatant flow after yielding exemplified appropriately by Herschel-Bulkley model with 100% confidence of fit. The present study is significant in formulation and handling, processing, and transport of emulsion and in understanding flocculation characteristics.