Control of bacterial attachment by fracture topography

Substrate properties as controlling parameters in attached algal cultivation

There is growing interest in attached algae cultivation systems because they could provide a more cost- and energy-efficient alternative to planktonic (suspended algae) cultivation systems for many applications. However, attached growth systems have been far less studied than planktonic systems and have largely emphasized algae strains of most interest for biofuels. New algal biorefinery pathways have assessed the commercial potentials of algal biomass beyond biofuel production and placed more emphasis on value-added products from that biomass. Therefore, algal strain selection criteria and biomass cultivation methods need to be updated to include additional strains for improved efficiency. One possible way of improving attached cultivation systems is through engineering substrate surface characteristics to boost algal adhesion and enable strain selective algal colonization and growth. This review explores the effect of substrate chemical and topographical characteristics on the cultivation of attached algae. It also highlights the importance of considering algal community structure and attachment mechanisms in investigating attached algae systems using the example of filamentous algae found in algal turf scrubber (ATS™) systems. KEY POINTS : • Attached algal cultivation is a promising alternative to planktonic cultivation. • Performance increase results from tuning surface qualities of attachment substrates. • Attachment adaptation of periphytic algae has innate potential for cultivation.

Inhibition of biofilm formation by rough shark skin-patterned surfaces

In this study, we investigate the microscale structure of shark skin denticles at abdomen (A) and fin (F) locations, analyze the roughness and wetting properties related to their microstructures, and evaluate the effect of the surface properties on early bacterial attachment and biofilm formation. Microstructural analysis by scanning electron microscopy and confocal laser scanning microscopy confirmed the length (A: 165-180 μm vs. F: 145-165 μm), width (A: 86-100 μm vs. F: 64-70 μm), height (A: 10.5-13.5 μm vs. F: 6.2-8.8 μm), and density (A: 110-130 denticles/mm²vs. F: 80-130 denticles/mm²) of the denticles. The results showed that the roughness and hydrophobicity properties were affected with slight differences in the microscale architecture. The denticles with a larger width, higher ridge, and denser overlap provided a rougher and more hydrophobic surface. The microscale structure not only affected surface properties but also the biological attachment process. The microscale topography of shark skin slightly promoted bacterial attachment at an early stage, but prevented bacteria from developing biofilms. This systematic investigation provides insights into the effects of the surface topography of shark skin on its anti-fouling mechanism, which will enable the future development of various products related to human activity, such as healthcare products, underwater devices and applications, and water treatment applications.