Horizontal Disposable Bioreactor for the Pre-Germination of Coffee Somatic Embryos

The pre-germination step corresponds to the conversion from the torpedo to the cotyledonary stage. It is achieved in large temporary immersion bioreactors (TIB). Up to 25,000 cotyledonary embryos (5 to 10 mm) can be collected per 10 L glass bottles, then directly transferred to the greenhouse. However, light distribution becomes rapidly a major constraint during embryo pre-germination as it can only penetrate the first few centimetres in the biomass. We hypothesized that a horizontal design will be more convenient than a vertical one, which is the usual shape of conventional vessels. As a result of a higher area/volume ratio, the embryos are more dispersed; consequently, the light transmittance to the embryos is increased. A very simple and cheap way to develop horizontal TIB is to include a rigid box inside a plastic bag. A higher growth performance is obtained which could be attributed to a better light distribution. This new TIB ("Box-in-Bags") is disposable allowing to reduce the production cost. Its advantages are listed.