ORIGINAL ARTICLE Modified basal culture medium improves proliferation of Dendrobium Sabin Blue’s protocorm-like bodies (PLBs) Chee Keong Chin 1,2 & Christine Stanly 1 & Bee Lynn Chew 1 & Sreeramanan Subramaniam 1,3,4,5 Received: 21 December 2020 /Accepted: 17 March 2021 # Plant Science and Biodiversity Centre, Slovak Academy of Sciences 2021 Abstract This study was carried out to reformulate half-strength Murashige and Skoog (MS) basal medium, one of the standard media for orchid tissue culture for protocorm-like bodies (PLB) culture of Dendrobium Sabin Blue. Initial PLB fresh mass of 0.5 g was inoculated in various culture treatments for six weeks of culture period. Alteration of half MS medium yielded a modified medium without Fe-EDTA and containing half-strength macronutrients, double-strength micronutrients, full-strength vitamins and 30 g/L sucrose. The modified medium enhanced the proliferation of PLBs by 23% (0.299 ± 0.017 g) as compared half MS medium (0.243 ± 0.012 g) on a dry mass basis. PLB suspension culture was established using liquid medium of the revised formula for a period of 7 weeks. Supplementing the modified medium with quarter-strength of Fe-EDTA is beneficial for long- term culture of PLBs. Improvement of PLB biomass through the use of modified culture medium devoid of plant growth regulators reduces production cost for micropropagation and secondary metabolite production. Besides, it can reduce the like- lihood of somaclonal variations related to the use of plant growth regulators in the culture medium. Keywords Basal medium . Macronutrients . Micronutrients . Vitamins . Suspension culture Introduction Dendrobium belongs to Orchidaceae, the largest family of flowering plants. It is the second-largest genus of the family distributed in the regions of Asia and Oceania (Zhan et al. 2020). Dendrobium made up 85% of the total tropical orchid trade market (Sheela 2008) and has become economically im- portant for the floriculture industry in Southeast Asian countries such as Thailand and Malaysia. Dendrobium orchids are used as traditional medicine in China, India, Australia and Nepal for various ailments such as diabetes, skin diseases, pain relief and fractured bones (Bulpitt et al. 2007; Hossain 2011; Tiwari et al. 2012; Subedi et al. 2013). Some of the most active chemical constituents of Dendrobium species are responsible for their pharmacological activities, many of which are age-related pathol- ogies (Cakova et al. 2017). These compounds have demonstrated antimicrobial, antimalarial and hepaprotective activities (Tian et al. 2015). More recently, Dendrobium orchids are explored for their application in skin care products (Kanlayavattanakul et al. 2018, 2019). Protocorm-like bodies (PLBs) are specialised embryogenic structures that are essential for the micropropagation of or- chids. Huan et al. (2004) highlighted that PLBs are somatic embryos through histological observation and Zhao et al. (2008) suggested regeneration of orchid plantlets through PLBs is a process of somatic embryogenesis. Later, PLBs were confirmed as somatic embryos through histochemical and immunofluorescence studies by Lee et al. ( 2013). Interest in PLBs stemmed from its use in orchid micropropagation. Besides its importance for mass propaga- tion (Young et al. 2000), PLBs have been recently used as a source of secondary metabolites. Enhanced polysaccharide production in PLBs of Dendrobium huoshanense was report- ed by Zha et al. (2007). Production of bioactive compounds * Sreeramanan Subramaniam sreeramanan@usm.my; sreeramanan@gmail.com 1 School of Biological Sciences, Universiti Sains Malaysia, 11800, Georgetown, Penang, Malaysia 2 Teacher Education Institute Malaysia, Tuanku Bainun Campus, Bukit Mertajam, 14000 Penang, Malaysia 3 Centre for Chemical Biology, Universiti Sains Malaysia, 11900 Bayan Lepas, Penang, Malaysia 4 School of Bioprocess Engineering, Universiti Malaysia Perlis, 02600 Arau, Perlis, Malaysia 5 National Poison Centre, Universiti Sains Malaysia, Georgetown, 11800 Penang, Malaysia Biologia https://doi.org/10.1007/s11756-021-00743-8