Abstract: The objective of this study was to optimize the extraction of polysaccharide from Lethariella cladonioides (NyL.) Krog through response surface methodology.Based on single factor experiments,extraction temperature,extraction duration,solid-liquid ratio were selected for Box-Behnken central composite design.By means of regression analysis,the results showed that the optimal conditions to extract polysaccharide from L.cladonioides were as follows:extraction temperature of 95 ℃,extraction duration of 2.5 h,solid-liquid ratio of 20 mL/g.Under these conditions,the extraction yield of polysaccharide reached 4.42%.Compared with the theoretical value (4.62%),the relative error was 4.3%.The results showed that the optimized process improved extraction efficiency.It can be used in practical forecasting.

Key words: Lethariella cladonioides (NyL.) Krog, Lichen polysaccharide, response surface methodology