Food waste composting is strongly influenced by microbial activity, particularly during the initial degradation and stabilization stages. The addition of bioactivators can introduce or stimulate microorganisms capable of accelerating organic matter decomposition. However, the response may vary depending on the type and dosage of bioactivator applied. This study investigated the effect of different bioactivator dosages on microbial density and composting performance of food waste mixed with chopped dry leaves. The experiment was conducted using three bioactivator types, namely stale-rice bioactivator (A1-A3), papaya bioactivator (B1-B3), and a combination of stale rice and papaya bioactivators (C1-C3), each applied at low, medium, and high dosages. Microbial density was determined using the Total Plate Count (TPC) method with serial dilution, while composting performance was evaluated based on temperature, pH, colour, odor, and the progression of decomposition. The results showed that the response of microbial density to increasing dosage was bioactivator-dependent. The papaya treatment exhibited the clearest dose-dependent increase, with microbial densities of 3.1 x 105, 8.7 x 105, and 4.2 x 106 CFU/mL in B1, B2, and B3, respectively. In contrast, stale rice and combined bioactivators showed non-linear responses, indicating that higher dosage did not necessarily produce a higher culturable microbial density. The E1/E1 control treatment showed slower composting progression without bioactivator addition, with the temperature gradually decreasing and pH stabilizing near neutral as decomposition progressed. Nevertheless, the high dose treatments generally showed stronger temperature responses, while pH gradually shifted from acidic to near-neutral conditions as decomposition progressed. Changes in colour and odor further supported the transition from active decomposition toward stabilization. These findings indicate that microbial density alone cannot fully explain composting performance, as microbial, oxygen conditions, and microbial interactions. Therefore, bioactivator dosage should be evaluated based on the integrated response of microbial density and physicochemical indicators to determine its effectiveness in accelerating food waste composting.
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