Screening for factors affecting dextransucrase production from Leuconostoc mesenteroides isolated from water kefir grains using statistical approach

Abstract

A leuconostoc strain was isolated from water kefir grains obtained from a household in Belgrade, Serbia. Strain was identified as Leuconostoc mesenteroides after biochemical and 16S rRNA sequencing studies. The isolated strain was found to produce dextransucrase. Culture medium and growth conditions for enzyme production were screened and optimized using the statistical design technique of Plackett-Burman [1]. Plackett-Burman design with variables viz. sucrose, yeast extract, beef extract, K2HPO4, Tween 80, incubation time, temperature and inoculum, was performed to screen main factors affecting enzyme production. Based on factorial design seventeen experiments were performed. Each factor was examined at two levels: -1 for low level and +1 for high level, and five center points were run to evaluate the linear and curvature effects of the variables. The enzyme activity was measured by estimating the liberated reducing sugars using 3,5-dinitrosalicylic acid method [2]. Among tested factors positive effect gave K2HPO4, Tween 80 and sucrose. Dextransucrase activity varied from 0.52 to 4.81 U/ml. Maximum activity was acquired from medium contained 50 g/l sucrose, 10 g/l yeast extract, 15 g/l beef extract , 60 g/l K2HPO4, 2g/l Tween 80, inoculated with 2% overnight culture and cultivated at 23oC for 16h. The resultats from statistical design technique of Plackett-Burman show that tested strain has high potential for dextransucrase production. Further optimization with positive factors should be done by the other statistical design technique, response surface methodology.