(585n) Comparative Analysis of Microwave and Pressurized Hot Water Fractionation for Producing Value-Added Oligosaccharides from Renewable Agricultural Feedstocks

Agricultural feedstocks, such as cotton stalk and sorghum stover, offer an affordable and renewable source of valuable fibers and platform chemicals. However, extracting these bio-products cost-effectively remains challenging. Among various lignocellulosic biomass fractionation methods, microwave technology stands out due to its rapid heating efficiency, reduced energy consumption, and operational simplicity. This study evaluates the mechanism of biomass disintegration by microwave through analyses of particle size, surface area, surface chemistry, and cellulose crystallinity. Microwave conditions, including temperature (150–190°C) and retention time (10–30 min), were optimized using response surface methodology to maximize oligosaccharide yields from liquid effluents. For comparison, the physico-chemical changes in microwave-treated biomass were assessed against those from pressurized hot water extraction. Results show that microwave extraction significantly reduces particle size (cotton – 26%, sorghum – 13%), cavitates secondary cell walls, depolymerizes and condenses lignin, and decreases cellulose crystallinity (8%) compared to pressurized hot water treatment. Optimal hemicellulose extraction efficiencies for cotton stalk and sorghum stover were achieved at 190°C/30 min and 170°C/30 min, respectively, with xylooligosaccharide yields of 51% (cotton) and 67% (sorghum). This study demonstrates that microwave extraction is a highly effective strategy for oligosaccharide extraction due to its accelerated physical and chemical disintegration of lignocellulosic feedstocks.