Optimization of Hydrolysis Conditions Using Response Surface Methodology to Maximize Reducing Sugar Yield from Panicum maximum (Guinea grass) Collected in Sri Lanka

Lignocellulosic biomass has gained significant global attention due to its potential as a sustainable alternative to fossil fuels. This study aimed to optimize the acid hydrolysis conditions to maximize reducing sugar yield from Panicum maximum plants collected in the Badulla District, Sri Lanka. While many studies have investigated hydrolysis of various lignocellulosic biomasses, few studies have focused specifically on Panicum maximum in a Sri Lankan Context. The whole plant composition was determined using a modified Van-Soest method. Hydrolysis was performed in a Teflon-lined hydrothermal reactor with 10% (w/v) solidliquid ratio, using H2SO4 as the catalyst. Hydrolysis parameters considered were temperature (120-180 °C), H2SO4 concentration (2-10% v/v), and reaction time (10-60 min). Reducing sugar was quantified with the 3,5-dinitrosalicylic acid (DNSA) method after the hydrolysis process. Response Surface Methodology (RSM) was employed for optimization using Central Composite Design (CCD) with replicated center point, and statistical analysis was performed using the Design-Expert Software. The biomass composition was cellulose (35.85 ± 2.88%), hemicellulose (22.25 ± 0.59%), lignin (6.47 ± 0.85%), ash (6.25 ± 0.33%), and soluble (29.17 ± 3.15%) (w/w). This higher holocellulose content (58.10% w/w) and low lignin were ideal for hydrolysis. ANOVA indicated that temperature (P=0.001) and H2SO4 concentration (P=0.001) significantly influence the hydrolysis process, while reaction time (P=0.612) was not significant as a single factor, but their interaction effect had a significant influence. The optimized acid hydrolysis conditions were 180 °C, 2% v/v H2SO4, and 32 min, with a predicted reducing sugar yield of 21.43% (w/w). Experiment validation yielded 21.68 ± 0.05 % (w/w), confirming the model accuracy. This study showed the potential of Panicum maximum as a promising lignocellulosic biomass for reducing sugar production. Keywords: Lignocellulosic biomass, Panicum maximum, Response Surface Methodology, Acid hydrolysis, Reducing sugar, Central Composite Design The Financial assistance from the Uva Wellassa University of Sri Lanka Research grant scheme (Grant No: UWU/RG/Mphil/2024/13) is acknowledged.