<![CDATA[This study aimed to optimize the biological pretreatment of sugar palm (Arenga pinnata) stem biomass using Streptomyces griseorubens through Response Surface Methodology (RSM), based on variations in pH, substrate loading, and incubation time. The lignocellulosic composition of the biomass was analyzed using the NREL method, while process optimization was performed using Design-Expert® version 13 with a Central Composite Design (CCD) comprising 20 experimental runs. Ligninolytic enzyme activities, including lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase, were evaluated. The pretreated biomass was subsequently subjected to saccharification followed by fermentation with Saccharomyces cerevisiae using the Separate Hydrolysis and Fermentation (SHF) approach. ANOVA showed that the model was significant for lignin degradation (p = 0.012 < 0.05). The optimum conditions were obtained at a substrate loading of 9 g, pH 4, and an incubation period of 21 days, resulting in 12.45% lignin degradation. Under these conditions, the cellulose content increased from 34.22% to 41.99%, and the hemicellulose content increased from 8.18% to 22.99%, whereas the lignin content decreased from 34.03% to 30.86%. Laccase, MnP, and LiP activities reached 11.32, 96.69, and 187.26 U/mL, respectively. Subsequent saccharification produced 1.847 g of reducing sugars from 5 g of biomass after 48 h, while fermentation yielded an ethanol concentration of 0.97% (w/w) after 72 h. These findings demonstrate the potential of S. griseorubens-mediated biological pretreatment to enhance the conversion of sugar palm stem biomass for second-generation bioethanol production.]]>
