A Singh, A Majumder, A Goyal
glucan, leuconostoc dextranicum, mutagenesis
A Singh, A Majumder, A Goyal. Mutagenesis of Leuconostoc dextranicum NRRL B-1146 for higher glucan production. The Internet Journal of Microbiology. 2008 Volume 7 Number 1.
The constitutive mutants of
Glucansucrases are extracellular proteins involved in the synthesis of α-glucans. Lactic acid bacteria produce a wide variety of exopolysaccharides [1,2].
The efficiency of established bioprocesses can be increased either by introducing more productive strains or by optimizing the cultivation medium itself . Development of new functional polysaccharides or glucans is important for food industry . Classical mutagenesis techniques can be used to generate mutants for improvement of enzyme and or glucan production. It can lead to production of new types of glucans. The selection for the desired strain and hunting for mutants however is cumbersome. Efficient mutagenesis and good planning pays off in time and labor. Mutants of
Materials and Methods
Mutagenesis of by Ultra Violet (UV) irradiation
Results and Discussion
Under the optimised mutagenesis conditions of dilution factor of 10 5 and 10 6 with 1 min duration of UV light exposure, 13 Petri dishes for each dilution factor were used in order to get sufficient number of mutants. After the UV light exposure, the clusters of colonies that grew around the edges of the Petri dishes were not picked and only those that grew at the centre of Petri dishes were taken (Table 1). From the Petri dishes of dilutions 10 5 and 10 6 , 137 colonies were visually screened based on their morphology and size and further grown on modified MRS agar Petri dishes. From 137 grown colonies, 97 mutants were again visually screened and glucan content of all was estimated using the microtitre format. From the analysis of the glucan produced by 97 mutants, 11 hyper-producer mutant strains were selected.
The Figure 1 shows the glucan content of each of these 11 hyper-producer mutant strains. The wild-type
The research work in part was supported by a project grant from Department of Biotechnology, Ministry of Science and Technology, New Delhi, India to AG.