Physicochemical Properties and Antibacterial Activity of Liquid Smoke from Leaves and Log Waste of Eucalyptus Tree in East Kalimantan, Indonesia

Abstract

Eucalyptus serves as a resource in the pulp and paper industry, with its leaves and logs being considered forest harvesting waste and possessing the potential to generate liquid smoke for secondary products. This study investigated the physicochemical properties of Eucalyptus pellita leaves and log liquid smoke sourced from East Kalimantan, along with their potential antibacterial activity. The liquid smoke production uses pyrolysis and distillation methods to upgrade the product's liquid smoke from grade 3 to grades 2 and 1. Analysis of physicochemical properties of this liquid smoke includes pH, specific gravity, and phytochemical content. The agar diffusion method was used to test for antibacterial activity against Propionibacterium acnes and Staphylococcus aureus. The research findings indicate that the liquid smoke derived from leaf and log waste of eucalyptus exhibits physicochemical properties that range from grade 3 to 1, conforming to Japanese standards across all grades concerning pH and color. In the case of eucalyptus leaf waste, the specific gravity is classified as grade 2 from distillation, measuring 1.0010 g mL⁻¹. For eucalyptus log waste, it is categorized as grade 3 from pyrolysis and grade 2 from distillation, with specific gravity values of 1.0112 g mL⁻¹ and 1.0081 g mL⁻¹, respectively. The results of the phytochemical tests on both raw materials contain alkaloid and terpenoid compounds. The inhibition zone and subsequent Duncan Multiple Range test demonstrate that liquid smoke obtained from leaves effectively suppresses the growth of Staphylococcus aureus, with concentrations of 50% (moderate), 75% (strong), and 100% (strong) exhibiting the greatest efficacy. An antibacterial assay of Propionibacterium acnes demonstrated that a concentration of 100% (strong) produced the most efficacious treatment. Eucalyptus log waste exhibited maximum effectiveness in the Staphylococcus aureus bacterial assay at concentrations of 75% and 100%. The Propionibacterium acnes bacterial assay demonstrated optimal efficacy at a concentration of 100%.