Lactobacillus spp. predominantly shows its presence as a normal mucosal flora of the mouth and intestine. Therefore, the objective of our research is to investigate the in-vitro conditions for the prospective of medically valuable biosurfactants (BSs) derived from Lactobacillus spp. Biosurfactant (BS) obtained from Lactobacillus spp. exhibit antibiofilm and antiadhesive activity against broad range of microbes. In the present study we investigated the production, purification and properties of key components of the cell-associated-biosurfactant (CABS) from Lactobacillus acidophilus NCIM 2903. Extracted, purified, freeze-dried CABS shows reduction in surface tension (SFT) of phosphate buffer saline (PBS @pH 7.0) from 71 to 26 mN/m and had a critical micelle concentration (CMC) of 23.6 mg/mL. The CABS showed reduction in interfacial tension (IFT) against various hydrocarbons and had effective spreading capability as reflected through the decrease in contact angle (CA) on different surfaces (polydimethylsiloxane - PDMS, Teflon tape, glass surface, polystyrene film and OHP sheet). The anionic nature of CABS displayed stability at different pH and temperatures and formed stable emulsions. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) revealed CABS as glycolipoprotein type. The Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed presence of multiple bands in a molecular range of 14.4 to 60 kDa, with prominent bands of 45 kDa. The CABS has significant antiadhesion and antibiofilm activity against tested bacterial strains. The current challenging situation is to develop methods or search for the molecules that will prevent the formations of biofilm on medical bioimplants of PDMS based materials. These findings are supportive for the use of Lactobacilli derived BS as potential antiadhesive agent on various surfaces of biomedical devices.

Background: Biomedical devices and implants are adversely affected by biofilm-associated infections that pose serious public health issues. Biosurfactants (BSs) can combat pathogenic biofilms through their antimicrobial, antibiofilm and antiadhesive capabilities. The objective of our research was to produce biosurfactant (BS) from Lactobacillus acidophilus NCIM 2903 and investigate its antibiofilm, antiadhesive potential using microfluidics strategies by mimicking the micro-environment of biofilm. Methods: Antibiofilm and antiadhesive potential was effectively evaluated using different methods like microfluidics assay, catheter assay, polydimethlysiloxane (PDMS) disc assay. Along with this chemical and physical characteristics of BS were also evaluated. Results: Cell free biosurfactant (CFBS) obtained was found to be effective against biofilm which was validated through the microfluidic (MF) or Lab on Chip (LOC) approach. The potency of CFBS was also evaluated on catheter tubing and PDMS surfaces (representative bioimplants). The efficacy of CFBS was also demonstrated through the reduction in surface tension, interfacial tension, contact angle and low critical micelle concentration. Conclusion: CFBS was found to be a potent antimicrobial and antibiofilm agent. We believe that perhaps this is the first report on demonstrating the inhibiting effect of Lactobacillus spp. derived CFBS against selected bacteria via LOC approach. These findings can be explored to design various BSs based formulations exhibiting antimicrobial, antibiofilm and antiadhesive potential for biomedical applications.

Omega transaminases (ω-TAs) can mediate the chiral amination of several unnatural substrates without the requirement of an α-COOH group and are highly relevant in the production of several pharmaceutical intermediates of commercial interest. Development of better variants of ω-TAs is hence essential for the biotransformation of unnatural substrates. We studied the active site architecture of the wild-type ω-TAs, to engineer enzymes that enhance the biotransformation of (R)-phenylacetylcarbinol to (1R, 2S)-norephedrine. Two such ω-TAs (TA_5182 and TA_2799) from P. putida KT2440 strain were overexpressed and purified as recombinant proteins. Crystal structures of TA_5182 were solved in two conformations, revealing significant movements of two highly flexible loops in these different states. The TA_2799 structure was determined as a complex with the cofactor pyridoxal 5'-phosphate (PLP) covalently bound to the catalytic K286 as an internal aldimine. Enzyme assays indicated that TA_2799 required a four-fold higher cofactor concentration than TA_5182 to achieve satisfactory biotransformation of (R)-PAC. A key mutation of L322F in TA_2799 drastically reduced (∼8-fold) the cofactor dependency of the TA_2799_L322F mutant enzyme, and the mutant remained active for 96 h at 30 °C. The crystal structure of the mutant enzyme revealed a key asparagine residue that mediates a hydrogen bonding network at the dimeric interface of the enzyme and is absent in TA_5182. The TA_5182_G119N mutant also showed enhanced cofactor affinity. The results of our studies will help generate Pseudomonad ω-TAs and ω-TAs from other organisms with high efficiency for asymmetric synthesis, for further applications in large-scale biotransformation processes.