Optimization of surface sterilization method for the isolation of endophytic fungi associated with Curcuma longa L. and their antibacterial activity

Medicinal plants have been extensively studied since ancient times and exploited for their various therapeutic applications. These plants have a repository of numerous beneficial chemical constituents imputable to their possible bioactive metabolites. Throughout the ages, turmeric (Curcuma longa L.) has a renowned nutritional and therapeutic importance. Each part of turmeric like rhizome, roots, stems, and leaves has its own medicinal properties. Inorder to recover endophytic mycoflora, epiphytic mycoflora must be eliminated via different sterilization techniques. In the present study, different sterilization methods have been assessed to isolate fungal endophytes from different parts of Curcuma longa L. The method involving the sequential washing of plant tissues with ethanol, sodium hypochlorite and ethanol used found more proficient in eliminating epiphytes. Five different surface sterilization treatments were evaluated for rhizome, roots, stem, and leaves of turmeric plant. Moreover, treatment 5 with combination of 70% ethanol for 1 min., followed by 2% sodium chloride for 2 to 3 min (2 min for leaf, and stem; 3 min for roots and rhizome) and 70 % ethanol for 30 seconds was found effective. A total of 38 fungal endophytes were recovered and screened for antibacterial activity against human pathogens Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa and Escherichia coli. Out of 38 isolates, only 11 (28.9%) isolates were found effective in inhibiting either one or all test pathogens. The results confirmed that turmeric plant of Haridwar region represents an extremely rich reservoir of potential endophytic mycoflora with possible source of novel bioactive metabolites. Further studies will resolute the potential of endophytic fungi for various biological activities such as antioxidant, antidiabetic and immunomodulatory.