The Architecture of Monospecific Microalgae Biofilms

Abstract

Microalgae biofilms have been proposed as an alternative to suspended cultures in commercial and biotechnological fields. However, little is known about their architecture that may strongly impact biofilm behavior, bioprocess stability, and productivity. In order to unravel the architecture of microalgae biofilms, four species of commercial interest were cultivated in microplates and characterized using a combination of confocal laser scanning microscopy and FTIR spectroscopy. In all the species, the biofilm biovolume and thickness increased over time and reached a plateau after seven days; however, the final biomass reached was very different. The roughness decreased during maturation, reflecting cell division and voids filling. The extracellular polymeric substances content of the matrix remained constant in some species, and increased over time in some others. Vertical profiles showed that young biofilms presented a maximum cell density at 20 μm above the substratum co-localized with matrix components. In mature biofilms, the maximum density of cells moved at a greater distance from the substratum (30–40 μm), whereas the maximum coverage of matrix components remained in a deeper layer. Carbohydrates and lipids were the main macromolecules changing during biofilm maturation. Our results revealed that the architecture of microalgae biofilms is species-specific. However, time similarly affects the structural and biochemical parameters.

Shear stress affects the architecture and cohesion of Chlorella vulgaris biofilms

“…This is also in agreement with what was postulated by Schnurr et al 39 , which proposed that the most active layers are present in the superficial portion of phototrophic biofilms. Besides, the different relationships (linear and exponential) between the attenuated light by the biofilms and their mean and max thickness suggest heterogeneity of cell density and structure within the biofilms 9 which impacted light attenuation. To the best of our knowledge, only few studies reported about the relationship between light attenuation and structural parameters in microalgae biofilms 39 , 40 .…”

“…The confocal microscope set-up was similar to that described in Fanesi et al 9 . Briefly, the images were acquired using an inverted Zeiss LSM700 confocal microscope (Carl Zeiss microscopy GmbH, Jena, Germany) equipped with a LD Plan-Neofluar 20×/0.4 Korr M27 objective with a 0.4 N.A.…”

“…peculiar spatial organization of cells and matrix components such as exopolysaccharides), only few works investigated how the architecture of microalgae biofilms changes as a function of the strain and growth conditions 5 – 10 . Recently, Fanesi et al 9 reported that microalgae biofilms architecture are species-specific. These results have important consequences for optimal process design to maximize productivity.…”

Biomass production and physiology of Chlorella vulgaris during the early stages of immobilized state are affected by light intensity and inoculum cell density

“…Among those factors, the impact of light, nutrients availability, temperature, pH and shear stress on growth rate and productivity have been studied, but mostly over long-term period of development (i.e. from weeks to months) [6,[19][20][21]. On the other hand, other factors such as substrate properties (e.g.…”

Surface plasma treatment (Ar/CF4) decreases biofouling on polycarbonate surfaces

“…diatoms) was reported as the dominant species on fouling release and antifouling coatings 34,39 . The four strains can develop biofilm in laboratory tests 40,41,42 , which is why they are currently used as model micro-organisms in the study of molecules or coatings with antibiofilm activities 43,44,45,46,47 . In these studies, P. purpureum is particularly notable due to its resistance to anti-biofilm molecules.…”