Physiochemical insights into substrate-diatom adhesion: Influence of surface properties on biofilm dynamics and productivity

Abstract

Diatoms play a significant role in biofilm formation due to their unique surface properties and robust extracellular polymeric substance (EPS) production. This study investigates the influence of substrate and diatom surface physiochemical parameters on adhesion and biofilm productivity. Using Amphora coffeiformis COR_3 and Nitschzia microcephala COR_2 as a model organism, results highlighted that the adhesion density varied significantly with substratum type. The strongly polar N. microcephala COR_2 cells (γ^p = 32.5 ± 0.89 mJ/m²) favored increased adhesion towards glass with adhesion density of 3.017 × 10⁵ cells/mm². Conversely, A. coffeiformis COR_3 with its intense dispersive component (γ^LW = 24.1 ± 0.08 mJ/m²) promoted strong adhesion towards PE with adhesion density of 2.938 × 10⁵ cells/mm². A. coffeiformis favored adhesion with hydrophobic substrates via van der Waals interactions, facilitated by hydrophobic methylene groups on its surface. While, N. microcephala promoted adhesion with the hydrophilic substrates through acid-base interactions and hydrogen bonding. These findings are further complemented by the varying EPS composition with A. coffeiformis producing protein-rich EPS on hydrophobic substrates, while N. microcephala releasing carbohydrate-rich EPS on hydrophilic substrates. This surface chemistry driven biofilm formation provides a baseline for optimizing the diatom-substrate pairs to enhance biofilm performance in industrial applications.