Roselle (Hibiscus sabdariffa) stem residues as a sustainable plant-based culture medium for isolation of endophytic bacteria

Abstract

Abstract Roselle ( Hibiscus sabdariffa L.) is a medicinal plant widely known for its phytochemical richness, yet its stem residues are often discarded despite potential microbiological value. This study focused on developing and optimizing a roselle stem–based plant culture medium to enhance the recovery and cultivation of endophytic bacteria associated with medicinal plants. Dried stem powders were prepared at varying concentrations (0.2, 0.5, 1, and 2 g L − 1 ) and evaluated as a nutrient source for microbial cultivation. A strain of Bacillus sonorensis was used to assess optimal medium concentration via optical density measurements over 240 h. The 1 g L − 1 concentration consistently exhibited the highest microbial growth, indicating its suitability as an alternative medium. Nutritional analysis of roselle stems confirmed the presence of key macronutrients and micronutrients supporting microbial development. The roselle-based medium recovered 43% of total colony-forming units (CFUs) compared to standard nutrient agar media. This highlights its effectiveness in cultivating microbial communities closely associated with medicinal plants. The findings suggest that roselle stems represent a sustainable, low-cost substrate for biopreparation and microbial exploration, contributing to green biotechnology and sustainable agriculture.