Process Optimization and Antimicrobial Activity of Natural Preservative Extracted from Bamboo Sawdust

  Objective  Optimum preparation and antibacterial properties of a natural preservative extracted from bamboo sawdust were studied.

  Method  Utilizing bamboo sawdust, a natural preservative was prepared with the ethyl acetate reflux method. Processing conditions were optimized by the response surface methodology based on the results of a single factor test. In vitro antimicrobial activity of the extract was determined.

  Result  The finalized process applied 300 W ultrasonic power on the mixture of solvent-to-substrate ratio at 20 ∶ 1 to extract at 89℃ for 2 h. The product yield reached 4.77%. The extracted preservative displayed peak antimicrobial effects on Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Aspergillus niger with the average inhibition diameters of 9.33 mm at a concentration of 0.025 00 g·mL⁻¹, 15.67 mm at a concentration of 0.012 5 0g·mL⁻¹, 10.00 mm at a concentration of 0.050 00 g·mL⁻¹, and 6.67 mm at a concentration of 0.100 00 g·mL⁻¹, respectively.

  Conclusion  The natural preservative prepared by the newly developed extraction method showed strong in vitro antimicrobial effect, and the optimized process could be upscaled to fully utilize the bamboo sawdust.