Scale-Up Transformed Shoot and Hairy Root Cultures of Salvia bulleyana in Bioreactor Systems: Process Optimization and Metabolite Productivity

To ensure large-scale production of plant-derived polyphenols, efficient and scalable in vitro culture systems are needed that can enable high biomass accumulation and secondary metabolite biosynthesis. The present study evaluates the suitability of transformed Salvia bulleyana shoot and hairy root cultures for biomass growth and phenolic compound production in different bioreactor systems, including two temporary immersion systems (PlantForm™ and RITA®) and a nutrient sprinkle bioreactor (NSB). A pronounced system- and organ-specific response was observed. In transformed shoot cultures, the RITA® bioreactor promoted high growth and volumetric productivity, although metabolite accumulation was lowered by partial hyperhydricity. In contrast, the PlantForm™ system provided more stable morphogenesis and higher polyphenol content, although less effective growth. In hairy root cultures, the NSB proved to be the most effective system, combining high biomass productivity with greater phenolic compound accumulation; total polyphenol content reached 65.1 mg/g DW, with rosmarinic acid (RA) constituting up to 78% of total phenolics. The highest volumetric productivity was achieved in NSB-grown hairy roots, reaching 837.9 mg/L total polyphenols and 651.3 mg/L RA. Secondary metabolism was further enhanced by elicitation with 100 μm methyl jasmonate applied under optimized bioreactor conditions. In transformed shoot cultures, elicitation increased RA accumulation by 63%, resulting in final productivity of 1164 mg/L RA, and 1250 mg/L total polyphenols. In hairy root cultures, RA accumulation increased by 44%, leading to final productivity of 795 mg/L RA and 933 mg/L total polyphenols. Our findings indicate that the balance between biomass growth and secondary metabolism in S. bulleyana cultures is determined by bioreactor configuration. The nutrient sprinkle bioreactor represents a highly effective platform for phenolic acid production in hairy root cultures, whereas temporary immersion systems can be successfully applied for transformed shoot cultivation. The combination of tailored bioreactor strategies with methyl jasmonate elicitation provides a promising approach for scalable production of high-value phenolic compounds in plant in vitro culture systems.