Structural Characterization of Functional Ingredient Levan Synthesized by Bacillus siamensis Isolated from Traditional Fermented Food in Thailand

Abstract

The rising global population continues to threaten the world’s food security. The discovery of new technologies to produce food of nutritional and functional properties is urgently needed. One beneficial food to humans of known nutritional value is the prebiotic levan. To address the problem, the present work is aimed at isolating levansucrase enzyme-producing microorganisms from traditional fermented food in Thailand. Bacterial colony morphology was observed for mucoidal consistency on culture plates. Isolated colonies were characterized morphologically by gram staining methods. Dinitrosalicylic acid (DNS) and thin-layer chromatography (TLC) reported the highest microbial enzyme activity of 8.51 IU/ml at 12 hours via hydrolysis and frutotransferase activities. Structural characterization of levan via Fourier-transform infrared spectroscopy (FTIR) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy showed β-(2,6)-fructofuranose linkages. The highest enzyme activity was exhibited by bacterium B-6 identified as Bacillus siamensis NR 11274.1 based on the 16s rDNA gene sequence analyses. Thus, the isolated bacterium from the traditional food was confirmed to produce levansucrase enzyme of high industrial importance for the synthesis of levan as a functional food.

Partial characterization of levan polymer from Pseudomonas fluorescens with significant cytotoxic and antioxidant activity

“…fluorescens strain ES strain was isolated from soil in Egypt, in a previous study (unpublished) and proved to be capable of producing characteristic feature of mucoidal consistency when grown on sucrose medium since levan polymer usually obtained from sucrose-based substrates by different microorganisms ( Tomulescu et al, 2016 ). This characteristic feature of the colony could be attributed to the production of an extracellular levansucrase enzyme which is capable of converting sucrose in the screening medium to exopolysaccharides in the form of β- d fructoside (levan polymer) ( Thakham et al, 2020 ), Levansucrase enzyme biosynthesis have been reported to occur in many gram-negative and gram-positive bacteria ( Benkeblia, 2013 ). Jathore et al, 2012a , Jathore et al, 2012b reported the production of levan by P .…”

“…fluorescens levan. The obtained results, showed three different large and strong peaks at the Wavenumber of 2930 and 2885 cm −1 and particularly at 3394 cm −1 corresponding to the stretching vibration bands C—H aliphatic asymmetric and symmetric methyl and methylene, respectively which being conjugated with the C O groups because of intermolecular hydrogen bonding ( Thakham et al, 2020 ). Moreover, the observed band at the Wavenumber of 1650 cm −1 might correspond to the characteristic of the C bond, which could be related to uronic acid groups.…”

“…The C—H bond α-type has an absorption peak of about 844 cm −1 , whereas that of the C—H bond β-type is about 891 cm −1 ( Jang et al, 2001 ). The weak peak at around 870 cm −1 might indicate the existence of β-glycosidic bond type pyranose in the polysaccharide ( Kuppusamy et al, 2015 , Jathore et al, 2012b , Yu et al, 2016 , Taylan et al, 2019 , Thakham et al, 2020 ).…”

Characterization of levansucrase produced by novel Bacillus siamensis and optimization of culture condition for levan biosynthesis

“…B. siamensis was previously isolated in our laboratory from fermented soybeans and was found to produce levan at high sucrose concentrations [ 33 ]. B. siamensis is a gram-positive rod bacterium that belongs to the Bacillus genus, which has members found throughout nature.…”

“…Our previous study established that the isolated novel strain of Bacillus siamensis from fermented soybeans possesses biocatalytic properties and found to produce levansucrase. The B. siamensis strain produced a novel extracellular levansucrase for levan biosynthesis induced by using sucrose as the substrate [ 33 ]. With the aim to reduce production costs and to efficiently produce levan, the current study characterized the levansucrase enzyme produced by the novel strain of B. siamensis and optimized culture conditions for levansucrase production and levan biosynthesis.…”