BACKGROUNDWith the increasing demand for microalgae it is clear that new industrial culturing techniques are needed. Current microalgae growth is done either in open or closed systems. In various situations, it has been reported that closed systems offer many advantages over open systems including lower contamination and better control over operating parameters. However, in industrial scale-up of closed tubular photobioreactors, hypercritical oxygen concentration is one of the dominating detrimental factors limiting the mass culture of microalgae in tubular systems. However, published accounts on alleviating oxygen stress imposed on large-scale tubular photobioreactors are scarce. RESULTSResults from this work showed that perfluorocarbon (PFC) emulsions, acting as gas-carrier vehicles, increased algal photosynthesis and biomass at least 4-fold in a closed tubular photobioreactor by decreasing dissolved oxygen concentration from 47% (generated in the photobioreactor without using PFC emulsions) to 4% after 9 days of culture. CONCLUSIONIn order to tackle the problem of high concentrations of dissolved oxygen strongly inhibiting microalgal biomass production, an innovative methodology has been developed which involves gradually supplying carbon dioxide and removing the accumulated oxygen through the use of PFC emulsions. (c) 2014 Society of Chemical Industry