Abstract

MUTAGENESIS OF LACTOBACILLUS SPECIES FOR THE GENERATION OF A MUTANT WITH HYPER-PRODUCING DEXTRANSUCRASE ACTIVITY

Sarangdhar Mithun* and Vora Dipak

Abstract

Dextran has been an indispensable part of the pharmaceutical industry since the World War II and a lot of research has been channelized for the production of pharmaceutically acceptable dextrans. The enzyme, which brings about the biological synthesis of dextran, is called dextransucrase (EC 2.4.1.5). It is produced by Lactic Acid Bacteria and particularly by strains of Leuconostoc mesenteroides. Extensive information is available for L.mesenteroides, however relatively less is known about the other dextran producers. Although each bacterial strain produces a unique glucan, a common structural feature of all dextrans is a high percentage (up to 95%) of α (1→6) linkages with a smaller proportion of either α (1→2), α (1→3), or α (1→4) linkages. This results in a highly branched dextran molecule. This study reports the strain improvement of Lactobacillus species by classical mutation technique using ultraviolet radiation, nitrosoguanidine and ethyl methanesulfonate, to achieve a mutant strain with higher dextransucrase activity. A large number of mutants were generated, cultured and tested for dextransucrase activity. The selected mutant gave considerably higher (23.44%) dextransucrase activity as compared to the wild-type strain.

Keywords: Lactic Acid Bacteria, Dextransucrase, Dextran, Mutation, UV radiations, NTG, EMS.