Antibacterial activity and stability of Stevia rebaudiana waste extract

The objective of the study was to evaluate the antibacterial activity and stability of Stevia rebaudiana waste extract.Stevia rebaudiana waste extract was obtained from flocculent waste of Stevia rebaudiana by acid acetone and ethyl acetate extraction.The antibacterial activity of Stevia rebaudiana waste extract was evaluated by filter paper diffusion and agar dilution method. The effect of temperature,ultraviolet light,p H and metal ion on the antibacterial activity of Stevia rebaudiana waste extract was also studied.The results showed that Stevia rebaudiana waste extract had antibacterial activity against Staphylococcus aureus,Bacillus cereus and Bacillus subtilis,with the minimal inhibitory concentration( or minimum bactericidal concentration) of 3.13( 6.25),12.5( 25),and 12.5( 12.5) mg /m L,respectively. However,it had no antibacterial activity against Escherichia coli and Samonella typhimurium.Stevia rebaudiana waste extract still showed good antibacterial activity after heating at 100 ° C for 20 min.The antibacterial activity against Bacillus cereus decreased after ultraviolet light treatment,and eliminated at p H < 7.0.Na+,K+and Ca2 +increased the antibacterial activity against Staphylococcus aureus and Bacillus cereus,while Fe2 +and Fe3 +decreased or deprived its antibacterial activity.In conclusion,Stevia rebaudiana waste extract had a broad prospect of development and utilization by using as a natural preservative.