Microalgal-bacterial co-cultivation on novel bio-coated supports: Evaluation of growth performance in submerged and permeated biofilm cultivation system with cost-benefit assessment

In microalgae mass production, co-cultivation with bacteria and biofilm immobilization hold promise, yet challenges persist in biofilm-based cultivation due to weak cohesion under stress. Hence, a novel bio-coating derived from spent medium and cells (extra-/intra-cellular organic matter from Cylindrotheca fusiformis and Escherichia coli) was applied to microporous membrane in submerged and permeated biofilm systems. Results showed a minimum 25 % improvement in biomass productivity (up to 45 g m⁻²) on bio-coated membranes in permeated system. Mucopolysaccharides in bio-coating facilitated biofilm development and encouraged a 10-fold higher AOM yield (defense mechanism against shearing force) in submerged systems, but biomass productivity was 10 times lower than permeated system. In permeated system, cells on IOM-coated membranes exhibited the highest biomass growth and lipid yield, potentially addressing the biomass-lipid trade-off. Permeated system with low operating cost around 69 $ kg⁻¹ was a viable cultivation approach, presenting an opportunity to optimize microalgae production facilities.