Response Surface Optimization of Medium Fermentation for Streptomyces prasinopilosus as An Antifungal against Ganoderma boninenseGanoderma boninense is one of the pathogenic fungi that cause basal stem rot (BPB) on oil palm plants. This research aims to study the effect of carbon sources, nitrogen sources, and minerals on the production of Streptomyces prasinopilosus active compounds. Lactose, yeast extract, and minerals are medium components that show a real influence on the production of S. prasinopilosus active compounds. Optimization of the factors that have significant influence was predicted by the second-order model, statistically through a central composite design (CCD). The highest S. prasinopilosus active compound production, with a medium composition of 44.77 g L-1 lactose, 13.02 g L-1 yeast extract, and 15.95 mL L-1 mineral solution, was predicted by the quadratic model to reach 32269366.338 peak area unit on high-performance liquid chromatography (HPLC). The verification of the mathematical model of the production of the active compounds through experiments in the laboratory was 27,203,907.310 peak area unit. This result was 15.7% lower compared to the result of the quadratic model. Optimization increased S. prasinopilosus active compound 9-fold compared to that before optimization.Keywords: active compound; G. boninense; optimization; RSM; S. prasinopilosus ABSTRAKGanoderma boninense merupakan salah satu jamur patogen yang menyebabkan penyakit busuk pangkal batang atau biasa disebut BPB pada tanaman kelapa sawit. Penelitian bertujuan mempelajari pengaruh sumber karbon, sumber nitrogen, dan mineral terhadap produksi senyawa aktif S. prasinopilosus. Laktosa, yeast extract, dan mineral adalah komponen medium yang menunjukkan pengaruh nyata terhadap produksi senyawa aktif S. prasinopilosus. Optimasi terhadap faktor yang berpengaruh nyata diprediksi dengan model orde dua melalui rancangan statistis central composite design (CCD). Produksi senyawa aktif S. prasinopilosus tertinggi diprediksi oleh model kuadratik mencapai 32269366,338 luasan puncak kromatografi cair kinerja tinggi (KCKT) dengan komposisi medium laktosa 44,77 g L-1, yeast extract 13,02 g L-1, dan larutan mineral 15,95 mL L-1. Verifikasi model matematis produksi senyawa aktif yang dihasilkan melalui percobaan di laboratorium adalah sebesar 27.203.907,310 luasan puncak kromatogram KCKT. Hasil ini lebih rendah 15,7% dibandingkan dengan model kuadratik hasil optimasi. Optimasi meningkatkan senyawa aktif S. prasinopilosus 9 kali lipat dibandingkan sebelum optimasi.