Effects of Plant Cultivation Density and Light Intensity on the Production of a Vaccine Against Swine Edema Disease in Transgenic Lettuce

抄録

Production technologies using closed-type plant production systems have been studied to assess their suitability for stable and uniform expression of biopharmaceutical materials in transgenic plants. We have developed a production system for a veterinary vaccine candidate against swine edema disease, using transgenic plants. In this paper, we report the combined effects of plant cultivation density and light intensity on the production levels of a vaccine candidate, the double repeated B subunit of Shiga toxin 2e (2×Stx2eB), in transgenic lettuce cultivated in a closed-type plant factory. Leaf dry-matter yield and total soluble protein (TSP) yield increased at higher plant cultivation densities, but in contrast, the 2×Stx2eB concentration in the plants tended to decrease with an increase in plant cultivation density, so that the 2×Stx2eB yield per unit area at lower plant cultivation density (44.4 plants m⁻²) was similar to or even higher than that obtained at the highest plant density (222.2 plants m⁻²). In addition, at the cultivation density (44.4 plants m⁻²), a photosynthesis photon flux density (PPFD) 200 (200±50 μmol m⁻² s⁻¹) was optimal in terms of maximizing the 2×Stx2eB yield and minimizing the electrical consumption of lighting. These results show that an optimal combination of plant cultivation density and light intensity is important in improving the productivity of recombinant protein expression systems in transgenic lettuce leaves when grown in a plant factory.