pH Dependent Dynamics of an Extended Biofilm: An In Situ Interferometry and Molecular Dynamics Approach

The fundamental physics-guided behavior of the extended region of a protein-based biofilm is ubiquitous in nature. The presence of high molecular weight proteins in such films alter the transport processes in a non-trivial way. Herein, an in situ interferometry-based microscopic approach is utilized to probe this in terms of the shape dependent interfacial phenomena in the extended thin film region of a gelatin-based biofilm. Interestingly, the pH, has been identified as an important parameter and has been varied to understand its effect on the extended film. A molecular dynamics simulation of a closely related protein at different pH has been performed as a model system to connect the experimental findings. One of the notable observations, is that, with increasing pH, the thicknesses of such films tend to decrease. It has been established, both in the experiments and MD simulation, that at high pH, the protein molecules remain well dispersed in the medium, whereas, in highly acidic conditions, the molecules tend to undergo agglomeration, increasing the thickness of the thin film. It is postulated that the findings of this study have potential applications in industrial biotechnology and food processing.