Preliminary studies on the production of high and low viscosity dextran by Leuconostoc spp.

Abstract

Isolates of Leuconostoc mesenteroides NRRL B-512 (F) and Leuconostoc dextranicum FPW-10 grew well and produced good yields of dextran from sucrose in unaerated or liquid surface fermentation and in shake flask culture which contained extract of wheat bran and dibasic potassium phosphate as nutrients. High temperature (20–26°C), unaerated fermentation of 10 and 20% sucrose (w/v) media by L. dextranicum FPW-10 resulted in viscosities of 80 and 430 cP, respectively. The corresponding weights of crude dextran obtained for every 100 g sucrose were 45 and 32·5 g. Enhancement of viscosities to 420 and 1280 cP occurred in corresponding shake flask cultures but without much change in yields. High temperature fermentations were completed in 24 h. The fermentation of 10 and 20% sucrose media under prolonged (72 h) unaerated low temperature (10–13°C) resulted in an increase in broth viscosities to 2300 and 2800 cP and yields to 50 g each, respectively. The reference L. mesenteroides B-512 culture performed similarly under these mentioned conditions. Factors such as concentration of wheat bran extract, inoculum size and fermentation period influenced the viscosity and yield of dextran in fermented broths.