Enhancing photosynthetic efficiency in Phalaenopsis amabilis through bioreactor innovations

Micro-propagation is the primary technique for the mass propagation of greenhouse orchids. However, various factors, including culture media and cultivation systems, influence the scaling-up and efficient commercialization of in vitro techniques. The utilization of liquid cultivation systems and bioreactors are relatively cost-effective and has attracted significant attention for mass production. In this study, we evaluated the effects of eight culture media, in both semi-solid and liquid forms, on the growth of in vitro mini-plantlets of Phalaenopsis orchids. We subsequently assessed the performance of four selected media: half-strength modified Murashige and Skoog (1/2 MMS), modified FAST (MFAST), and two simplified media (SM1 and SM2), across four types of cultivation systems, including semi-solid media in glass jars, liquid media in a permanent immersion system using Erlenmeyer flasks on a shaker (PIS), and a temporary immersion system (TIS) in two forms: FA-Bio bioreactor (TIS-FA-Bio) and RITA^® bioreactor (TIS-RITA^®).

The results indicated that the optimal culture medium for orchid growth depends on the cultivation system used. Among the eight evaluated semi-solid and liquid media, the highest plant growth was observed in the SM2 medium, attributed to the presence of additives (banana powder and activated charcoal), two types of sugar (with high carbon content), and small amounts of nickel and ascorbic acid. The high carbon content in the SM2 liquid medium, combined with the temporary immersion explants in a large volume of medium in the TIS-RITA®, resulted in the highest total carbohydrate content and enhanced plant growth. The maximum quantum efficiency of photosystem II (F_v/F_m) and the number of plantlets per liter in SM2 semi-solid medium were higher than those in the 1/2 MMS semi-solid medium (control), leading to a 61.6% reduction in production costs. Furthermore, the number of plantlets per liter in the TIS-FA-Bio containing SM2 (10.8 USD) was higher than in TIS-RITA® with 1/2 MMS (39.3 USD), resulting in a 72.5% decrease in production costs due to a lower volume of medium and the use of inexpensive equipment.

We recommend the use of SM2 in TIS-FA-Bio and TIS-RITA® for economical and efficient mass propagation of Phalaenopsis orchid.