## 3 Results
### Analysis of Physico-Chemical Properties of Biosurfactant  
Analysis of physical properties like SFT, IFT, CMC, CA, emulsification properties and ionic character proved the effectiveness of CFBS. The SFT of PBS was reduced from 72 to 27 mN/m with a CMC 625 \(\upmu\)g/mL (Figure 2A). Figure 2B represents the semi-logarithmic reflection of the same CMC value from SFT versus CFBS concentration. Other physical properties like IFT, CA, EA, ES also confirmed the efficacy of CFBS produced by NCIM 2903 with great certainty. The IFT measurements with immiscible liquids (hydrocarbons), showed lowest IFT against benzene (1.47 mN/m) followed by kerosene, o-xylene, n-hexane (Figure 3). There was good reduction in IFT values by CFBS against all hydrocarbons tested in comparison to other synthetic surfactants. Effective spreading abilities for CFBS were tested through the measurement of CA. The highest reduction in CA was observed on polystyrene (From \(\theta=90^{\circ}\) to \(49^{\circ}\)) and PDMS (from \(\theta=115^{\circ}\) to \(74^{\circ}\)) followed by Teflon (from \(\theta=115^{\circ}\) to \(75^{\circ}\)). Polystyrene and PDMS surfaces are used regularly in  
Figure 3: Measurement of interfacial tension (IFT) mN/m for biosurfactant obtained from _L. acidophilus_ NCIM 2903 and synthetic surfactants against water insoluble liquids. Control: Phosphate buffer saline; CFBS: Cell free biosurfactant; AOT: Aerosol OT; CTAB: Cetyl trimethyl ammonium bromide; SDS: Sodium dodecyl sulphate. Figure 2: **(A)** Variation in surface tension and **(B)** semi-logarithmic reflection of critical micelle concentration (CMC) value from surface tension (SFT) (mN/m) versus biosurfactant (BS) concentration. biomedical industries. CA on OHP transparent sheet was reduced from \(\theta=69^{\circ}\) to \(44^{\circ}\). However, on highly hydrophilic surface like glass; there was no significant reduction in CA values (from \(\theta=39^{\circ}\) to \(25^{\circ}\)) (Figure 4). The CA measurements for CFBS derived from _Lactobacillus_ sp. have seldom been reported in literature. The emulsification capacity and stabilization activity of CFBS against different hydrocarbons-liquids (water insoluble) analysis showed that CFBS has relative EV between 25-65% and ES between 45-87% after 24 h. The highest EV (65%) was seen against n-decane with 87% of ES. CFBS demonstrated good EV (46%) and ES (87%) with xylene. Treatment of CFBS (CMC solution) at different pH (2.0 to 12.0) indicated higher stability between the pH of 6-10 and lowest SFT value at pH 7.0 indicating the potency of CFBS at neutral to alkaline conditions. However, treatment of BS at acidic pH; result its precipitation. Regarding the temperature effects, CFBS worked well at different temperatures (4, 30, 70 and 121 \({}^{\circ}\)C). Determination of ionic character by agar double diffusion technique indicated passive diffusion between CTAB (cationic compounds) and CFBS proving the presence of anionic charge on CFBS (Figure 5). A prominent line of precipitation formed on soft gel helped rapid determination of ionic character of CFBS. Sugar and lipid moieties were detected using TLC confirming the presence of glycolipid typed CFBS. The chemical composition was confirmed by FTIR analysis (Figure 6). Figure 4: Measurement of contact angle (CA) (degrees) for biosurfactant (BS) obtained from _L. acidophilus_ NCIM 2903 on different surfaces, OHP: Overhead Projector Transparent sheet; PDMS: polydimethysiloxane. Figure 5: Double diffusion of cationic surfactant (**B**) (positively charged) Cetyl trimethyl ammonium bromide (CTAB) against biosurfactant (BS) (**A**) on agar plate indicating a line of precipitation due to formation of ionic pair. The peak at 3320 cm\({}^{-1}\) depicts the presence of OH stretching. The presence of hydrocarbons is confirmed by the peak at 2900 cm\({}^{-1}\). The peaks at 1730 cm\({}^{-1}\) significantly denote the presence C=O stretching in ester bond.