BACKGROUND The use of bioreactors that mimic industrial reality is essential if knowledge transfer is desired. This is particularly important once filamentous microbes face harsh conditions hindering the formation of biofilms in some types of bioreactors and thus diminishing their ability to perform biotransformation or production of secondary metabolites. Airlift bioreactors can circumvent such problems; however, the lack of consensus regarding riser and downcomer partition persists. The use of golden ratio is a possibility to be considered. Our proposition was to evaluate the hydrodynamic performance and mass transfer in split-rectangle-internal loop airlift bioreactors (SRILAB) using a golden ratio partition. RESULTS In a general way, results revealed that a partition of A(r)/A(d)(1.618) presents better and more desirable characteristics than A(d)/A(r)(1.618) for linear liquid velocity (U-L), mixing time (t(M)), gas holdup (epsilon(G)), and volumetric oxygen transfer coefficient (k(L)a). Such behavior was observed even when the SRILAB operated under different linear gas velocities (U-G) regimens (0.5-1.5 vvm) and Newtonian and non-Newtonian bulk fluids. CONCLUSION Such results support the idea of using the golden ratio as riser-to-downcomer partitioning parameter in airlift bioreactors. (c) 2018 Society of Chemical Industry