Abstract Centrifugal pumps are widely used in tubular photobioreactors (PBRs) due to their efficiency, but they generate significant hydrodynamic stress, which can affect filamentous microalgae like Limnospira platensis . This study analyzed the effect of such stress on L. platensis cultivation at both pilot- (2.6 m 3 ) and industrial- (120 m 3 ) scales. The culture's productivity was assessed, together with filament integrity, biochemical composition (protein and phycocyanin), and energy use. In the pilot-scale tubular PBR, the pump caused rapid filament fragmentation, with 90% of the filaments smaller than 200 μm within 24 h. Yet, the culture maintained a high volumetric productivity of 0.154 g L⁻ 1 day⁻ 1 , three times higher than the 0.049 g L⁻ 1 day⁻ 1 of the raceway ponds. When transferred to a low-shear RW, filament length demonstrated rapid recovery, with more than 40% of the filaments longer than 200 μm after just 6 days. At the industrial scale, filament breakage was less severe, but energy use was 50 times higher than in the industrial raceways. A scale-up model showed that using tubular PBRs for inoculum production speeds up the scale-up process by 13 days. These results show that shear forces from centrifugal pumps change filament morphology, but do not compromise the culture's productivity or long-term viability, positioning the use of tubular PBRs as a strategic approach for fast inoculum production in a hybrid cultivation system.
Guerra et al. (2026) studied this question.