Production, Characterization and Enhancement of Biopolymer Levan from Lactobacillus fermentum SHN1

Abstract

Levan is a highly water-soluble biopolymer that has extensive applications in the pharmaceutical, personal care, food, and industrial fields. Lactobacillus fermentum SHN1 was isolated from milk and dairy products as an exopolysaccharide (levan) producer and identified according to morphological, biochemical tests and using the 16S rRNA gene sequencing. The sequence alignment in the gene bank indicated that the isolate has a high percentage of similarity (100%) to the recovered sequence of Lactobacillus fermentum isolate. The produced biopolymer was characterized as levan by FTIR, 1H-NMR, and 13C-NMR spectroscopy. The effect of various nutritional and physical factors including pH, carbon source, sucrose concentration, nitrogen source, inoculum size, and incubation period, on the synthesis of levan by L. fermentum SHN1 was studied. The findings indicated that the optimal carbon source for the production of levan was 100 g/L sucrose, yielded of 25.95 g/L. Additionally, a combination of peptone + yeast extract at a ratio of 2:0.5 was identified as the most effective nitrogen source for levan production, giving in a yield of 24.21 g/L. L. fermentum SHN1 produces the greatest quantity of levan, 23.89 g/L, under a pH of 6.5 and an inoculum size of 1%, resulting in a yield of 25 g/L. The most favorable period for incubation was 48 hours, resulting in a production yield of 24.87 g/L.