Optimization of Plant Growth Regulators and Bioreactor Systems for Efficient In Vitro Shoot Multiplication and Elongation of Amorphophallus muelleri Blume

Porang (<em>Amorphophallus muelleri</em> Blume), an Indonesian endemic species rich in glucomannan, is widely utilized in food industries for its health benefits. However, its traditional vegetative propagation through bulbils produces limited plants, necessitating an efficient <em>in vitro</em> multiplication system. This study aimed to optimize plant growth regulator combinations and bioreactor systems for enhanced shoot induction and elongation of <em>A. muelleri</em>. During the initiation and induction stages, combinations of thidiazuron (TDZ) with benzylaminopurine (BAP) or kinetin at concentrations ranging from 0 to 1.00 mg l⁻¹ were applied to solid MS media and observed for 8 weeks. The combination of TDZ 0.50 mg l⁻¹ + BAP 1.00 mg l⁻¹ produced the fastest shoot induction (32.34±2.52 days), while TDZ 0.75 mg l⁻¹ + BAP 0.75 mg l⁻¹ resulted in the highest shoot number (76.33±22.81 shoots explant⁻¹) and 100% shoot formation. TDZ combined with kinetin had no significant effect on induction parameters. For elongation, shoots induced from TDZ 0.75 mg l⁻¹ + BAP 0.75 mg l⁻¹ medium were cultured in two bioreactor systems: a Temporary Immersion System (TIS) and a Balloon Type Bubble Bioreactor (BTBB). The BTBB significantly outperformed the TIS, yielding 85.2±3.35 shoots explant⁻¹ with an average shoot length of 5.67±1.13 mm after 4 weeks. These results indicate that the synergistic use of TDZ and BAP, combined with the BTBB system, substantially improves <em>in vitro</em> shoot multiplication and elongation of porang, providing a reliable approach for its large-scale propagation and conservation.