LAUSR

The major objective of the current study was to investigate the potential effects of differential pH levels on culture development and production of steviol glycosides and other polyphenolics content in submerge root cultures of Stevia rebaudiana. In vitro grown cultures require an optimum pH level for rapid growth and uniform production of secondary metabolites. Herein, varying media pH levels (5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 and 6.0) significantly influenced fresh and dry biomasses of adventitious root cultures. Among tested levels, adventitious root cultures favored high media pH (6.0) for accumulation of maximum fresh biomass (112.86 g l−1) and dry biomass (8.29 g l−1). In this study, we observed that lower pH level (5.1) strongly supported the production of steviosides (79.48 mg/g-DW) and rebaudioside-A (13.10 mg/g-DW) contents but reduced the polyphenolics content in adventitious cultures. However, dulcoside contents (2.57 mg/g-DW) in adventitious root cultures were found in higher quantities at pH level 5.8. Similarly, maximum total phenolics (70.06 mg/g-DW) and flavonoids (50.19 mg/g-DW) were observed on media having 5.8-pH level. The same pH level also improved DPPH-radical scavenging activities (92.67%). This study will offer an approach to enhance medicinal products in the in vitro tissues, rather than to over-exploit the wild plants and ultimately putting them on the brink of being endangered. Furthermore, the consistent production of secondary metabolites in these cultures could be scaled-up on bioreactor level, which will ultimately affect the society by potential introduction of cost-effective and biologically stable medicinal drugs.