Plant cell culture in bioreactors is an enabling tool for large scale production of clonal elite plants in agriculture, horticulture, forestry, pharmaceutical sectors, and for biofuel production. Advantages of bioreactors for plant cell culture have resulted in various types of bioreactors differing in design, operating technologies, instrumentations, and construction of culture vessels. In this review, different types of bioreactors for clonal propagation of plants and secondary metabolites production are discussed. Mechanical and biochemical parameters associated with bioreactor design, such as aeration, flow rate, mixing, dissolved oxygen, composition of built-up gas in the headspace, and pH of the medium, are pivotal for cell morphology, growth, and development of cells within tissues, embryos, and organs. The differences in such parameters for different bioreactor designs are described here, and correlated to the plant materials that have been successfully cultured in different types of bioreactors.

Somatic embryogenesis offers many benefits for clonal propagation in large-scale plant production of conifers. A key rate-limiting step is the conversion from early-stage somatic embryos in pro-embryogenic masses (PEMs) to the maturation stage. Immature embryos in PEMs are present at different developmental stages, where some are unable to respond to the maturation treatment, thus limiting yields of mature embryos. Synchronization of early somatic embryo development in PEMs could greatly improve subsequent yields of mature embryos. A temporary immersion bioreactor designed for Norway spruce (Picea abies (L.) H.Karst.) was used in this study. Through a specific system for dispersion, connected tissue of PEMs, composed of immature embryos grown in liquid medium in the temporary immersion bioreactors or on solid medium as a control, was dispersed and redistributed in a more uniform spatial arrangement. It was demonstrated that development of mature embryos could be significantly stimulated by dispersion, compared to controls, in both medium types. Synchronization of maturation was evaluated by a statistical approach. The present study shows that the yield of mature embryos from dispersed PEMs was three to five times higher than that from non-dispersed controls in three of four cell lines of Norway spruce tested, both in bioreactors and on solid medium.Electronic supplementary materialThe online version of this article (10.1007/s11627-018-9911-4) contains supplementary material, which is available to authorized users.