Abstract: Extration of Pectin by protopectinase could be used to reduce the shortcomings in current industry processing of pectin production as well as to stabilize the pectin with high quality. Crude propectinase was obtained by fermentation of Aspergillus sp XZ-131. The cirtus peel, containing protopectin was reacted with crude protopectinase in different conditions, such as varying pH, ratio of peel to water, reaction time and temperature, in order to find out the optimum conditions for extraction of pectin. The results were showed as follows: cirtus peel suspended in pH3.0 fermentation broth (1:2W/V) and the reaction proceeded for 5 hours at 25℃. 35.7% of pectin was extracted in these condition.

Key words: protopectinase, pectin producing, reaction optimum