Optimization of nutritional conditions using a temporary immersion bioreactor system for the growth of Bletilla striata pseudobulbs and accumulation of polysaccharides

Abstract

Abstract A temporary immersion bioreactor system (TIBS) has been explored as a possible way for Bletilla striata pseudobulbs enlargement and accumulation of polysaccharides under a fed-batch culture method. The culture was established in TIBS to optimize feeding parameters for polysaccharides accumulation and pseudobulb enlargement under controlled conditions, included 1/2 MS, 40 g/L sucrose; 60 g/L potato lixivium; 0.5 mg/L NAA and an immersion rate of 3 min at every 6-hour interval. Results showed that the combined feeding and elicitation strategy (2% sucrose and 0.25 mmol/L Me-JA) was suitable for the enlargement of pseudobulbs (diameter: 6.78 ± 0.16 mm) and the biosynthesis of polysaccharides (14.49 ± 0.45 mg/g). The optimum plant growth (plant height: 123.97 ± 5.42 mm, leaf width: 7.78 ± 0.32 mm and stem diameter: 2.10 ± 0.07 mm) was obtained by the inoculation of nitrogen feed source of NO3−: NH4+ with a 3:1 ratio. At this stage, the corresponding B. striata pseudobulb enlargement and polysaccharide content were decreased to 6.1 ± 0.2 mm and 8.51 ± 0.1 mg/g, respectively, while the highest pseudobulb enlargement (7.21 ± 0.17 mm) and polysaccharide content (12.94 ± 0.35 mg/g) were optimized when inoculated the NO3−: NH4+ with molar ratio of a 2:2. In conclusion, the optimal carbon and nitrogen source supplements effectively induced the pseudobulb enlargement and polysaccharides accumulation. Overall, the present combination of TIBS and feeding strategy constitutes advancement for the industrial production of pseudobulbs as well as polysaccharides, as comparison with the conventional process.