Understanding photosynthetic biofilm productivity and structure through 2D simulation

Abstract

We present a spatial model describing the growth of a photosynthetic microalgae biofilm. In this 2D-model we consider photosynthesis, cell carbon accumulation, extracellular matrix excretion, and mortality. The rate of each of these mechanisms is given by kinetic laws regulated by light, nitrate, oxygen and inorganic carbon. The model is based on mixture theory and the behaviour of each component is defined on one hand by mass conservation, which takes into account biological features of the system, and on the other hand by conservation of momentum, which expresses the physical properties of the components. The model simulates the biofilm structural dynamics following an initial colonization phase. It shows that a 75 μm thick active region drives the biofilm development. We then determine the optimal harvesting period and biofilm height which maximize productivity. Finally, different harvesting patterns are tested and their effect on biofilm structure are discussed. The optimal strategy differs whether the objective is to recover the total biofilm or just the algal biomass.

Two cyanobacterial response regulators with diguanylate cyclase activity, Rre2 and Rre8, participate in biofilm formation

“…EPS, the building block of biofilms, is derived from inorganic CO 2 that is fixed through photosynthesis, thereby linking biofilm formation and diurnal changes in photosynthesis (McCormick et al, 2011; Polizzi et al, 2022). Moreover, the cyclic electron transport around PSI is enhanced in Synechocystis under salt stress (Allakhverdiev & Murata, 2008; Hagemann, 2011).…”

Migration of surface-associated microbial communities in spaceflight habitats

“…Another possible source of fresh food is the cultivation J o u r n a l P r e -p r o o f of microalgae with nutritive interest (lipids, vitamines…). In order to limit the use of water and energy, biofilm-based microalgae cultivation systems on surfaces are developed [158]. Alternatively, bioprinting of microalgae cells with controlled patterns in hydrogels could allow the formation of a synthetic biofilm with optimum exposure to light and nutrients [258] [259].…”

“…We simulated the growth of a micro-alga biofilm subject to terrestrial or microgravity. The model is a mixture model [158] coupling a fluid dynamics model to a reaction-diffusion-convection model of biofilm dynamics including biomass growth and consumption of diffusive nutrients and CO2. Compared to [158], an additional force is added to the movement conservation equation modelling the gravity-dependent sedimentation as a net force between a gravitational force and a buoyant force [154].…”

“…The model is a mixture model [158] coupling a fluid dynamics model to a reaction-diffusion-convection model of biofilm dynamics including biomass growth and consumption of diffusive nutrients and CO2. Compared to [158], an additional force is added to the movement conservation equation modelling the gravity-dependent sedimentation as a net force between a gravitational force and a buoyant force [154]. We can observe that micro-gravity impacts the spatial structure of the biofilm and therefore the resulting substrate consumption and the overall biofilm growth.…”

Experimental and theoretical investigations of rotating algae biofilm reactors (RABRs): Areal productivity, nutrient recovery, and energy efficiency

“…For example, in Bara et al (2019), the authors investigated the impact of sunlight intensity and exposure on the areal productivity of the biofilm in Rotating Algae Biofilm (RAB). A spatial model that describes the growth dynamics of a photosynthetic algae biofilm was developed in Polizzi et al (2022), while a time–space model for algae biofilm growth for biofuel production was proposed in Polizzi et al (2017). To optimize and control the RABR, parameter studies of rotation velocity and its effect on areal productivity have been conducted, and harvesting strategies, such as the frequency and proportion of harvesting, have been modeled to optimize productivity (Jones et al, 2023; Polizzi et al, 2022).…”