Journal of Pure and Applied MicrobiologyVol. 7 No. 4

Purification and Immobilization of Dextransucrase from Immobilized Lactobacillus acidophilus ST76480.01

Aliaa M. El-Borai*, Rania M.A. Abedin, Mona Abo Shall and Samy A. El-Assar

Botany and Microbiology Department, Faculty of Science, Alexandria University, Egypt.

Received on 10 August 2013 and accepted on 20 September 2013

 

ABSTRACT

Production of dextran by immobilized Lactobacillus acidophilus ST76480.01was intensively investigated. Adsorption was the most suitable immobilization technique for production of dextran and Luffa pulp was the preferred matrix recording (4.74 U/mg protein) of dextransucrase activity and (5.28 mg/ml) of dextran yield. During semi continuous cultivation, adsorbed cells on Luffa pulp retained about 84% of dextransucrase activity and 26% of dextran yield respectively at the 8th run. The fraction obtained at 65% ammonium sulphate saturation was the richest in its protein content contributing about 4.05% of the total recovered protein, and the highest recovery of dextransucrase activity, about 3.34 % of the culture supernatant. By immobilizing of dextransucrase on chitosan, the highest dextransucrase activity (5.06 U/mg protein) was obtained, achieving 4.4 fold increase than that of entrapping one in alginate, and 2.8 fold of the free enzyme. The enzyme showed a high thermal stability and retained about 60% and 33% of its original activity when heated for 30 min and 60 min respectively at 80oC. MnCl2, CaCl2 and KCl enhanced the activity for both free and immobilized enzymes, while ions, as HgCl2, BaCl2, CuSO4 and EDTA, showed different degrees of inhibition of the tested dextransucrase activity.

Keywords : Dextran, Dextransucrase, Purification, Immobilization.