Palm oil decanter cake wastes as alternative nutrient sources for production of enzymes from Streptomyces philanthi RM-1-138 and the efficacy of its culture filtrate as an antimicrobial agent against plant pathogenic fungi and bacteria

Valorization of solid wastes from palm oil mill based medium for the production of enzyme from Streptomyces philanthi RM-1-138 and the efficacy of its culture filtrate as an antimicrobial agent against plant pathogenic fungi and bacteria were investigated. Solid-state fermentation of S. philanthi RM-1-138 grown in oil palm decanter cake (OPDC), palm pressed fiber (PPF), and OPDC + PPF (1:1) for production of enzymes was investigated after 12 days incubation. OPDC was the best substrate as it gave the highest enzyme activity of xylanase, cellulase, and chitinase (at 5.21 ± 0.26, 3.75 ± 0.38, and 0.48 ± 0.01 U mL⁻¹ respectively) at 10 days incubation. In addition, the production of β-1,3-glucanase was not detected in all raw materials. From our previous studies, the culture filtrate of this strain was found to contain bioactive compounds. In this study, the efficacy of the culture filtrate RM-1-138 produced under the optimal conditions (60% moisture content with the initial pH at 7.0) was evaluated against three strains each of plant pathogenic fungi and bacteria. Its efficacy was most pronounced in Ganoderma boninense (74.33%) followed by Curvularia oryzae (64.67%) and Ceratocystis paradoxa TT1 (58.33%), respectively. Its efficacy against Xanthomonas axonopodis pv. glycines, X. oryzae pv. oryzae, and X. campestris pv. campestris were low and not significantly different (P > 0.05) (19.17, 18.50, and 18.33 mm, respectively). With these results, the OPDC had a high potential to be utilized as substrate for the production of enzymes and antimicrobial agent by S. philanthi RM-1-138.