Structural and Rheological Properties of Exopolysaccharides Produced by Some Lactic Acid Bacterial Strains Isolated from Palm Wine

Aims: This study evaluated the physical, chemical and rheological properties of exopolysaccharides (EPSs) produced by Lactic Acid Bacteria (LAB) isolated from palm wine. Materials and Methods: EPSs from palm wine LAB strains were produced on 6% sucrose broth, purified and freeze-dried prior to analyses. Molecular weights (MW), rheological and structural composition (functional groups) of the EPSs were determined using standard methods and Fourier transform infrared spectroscopy (FTIR). Results: The average MW of the EPSs ranged from 2.02×106 to 6.53×106 Da while the flow index (n) values ranged from 0.03-3.13 at 0.2%, 0.06-1.51 at 0.4%, 0.38 - 1.85 at 0.6%, 0.14 - 2.26 at 0.8% and 0.55 - 6.42 at 1% concentrations at elevated temperatures for EPS solutions from the ten LAB species. The FTIR spectrum revealed prominent peaks of various groups of OH (3420 cm-1) and CH3 bending (2090 cm-1) in all the EPSs corresponding to both hydroxyl and amine groups, and aliphatic C-H bonds, respectively. EPS synthesized by Leuconostoc lactis, Lactococcus lactis subsp lactis and Lactiplantibacillus plantarum showed weak absorption peaks (1148 – 1145 cm-1) indicating the C-O-C and C-O bonds, while absorption peaks of Lactobacillus lactis, Lactobacillus acidophilus and Lactiplantibacillus plantarum (1267 – 1253 cm-1) indicated O- acetyl ester and other non-sugar components. Conclusions: The FTIR spectra, rheological properties and molecular weight of EPSs synthesized by the ten LAB strains indicated potentials that could be exploited in different industrial applications, and as stabilizers in food industries

Diversity of Bacterial Community in Fermentation of African Oil Bean Seeds (Pentaciethra macrophylla Benth) by comparison of 16S rRNA Gene Fragments.

Aims: The microbial diversity, fermentation dynamic and the predominant microorganisms involved in the fermentation of African oil bean (Pentaciethra macrophylla Benth) seeds to “Ugba” traditional African food in Eastern Nigeria were investigated by analyzing the microbial community DNA of the food using sequences of their 16S rRNA genes fragment analysis. Study Design: Universal bacterial conserved 16S rRNA gene region was used to study bacterial dynamics as well as the diversity during fermentation stages. Predominant microorganisms were investigated with the view to establishing the best possible starter culture for the production of high flavoured “Ugba”. Place and Duration of Study: Biotechnology Centre of Federal University of Agriculture, Abeokuta, Ogun State, Nigeria, between January 2007 and May 2009. Methodology: Raw seeds were boiled for two hours for easy removal of the seed coats. Peeled seed cotyledons were sliced, cooked for 4hrs until softened. Sliced cotyledons were washed, wrapped in local leafs for fermentation for a period of 96hrs. Sampling for analysis was performed, at every 24 hours interval. Bacterial Community of freshly fermenting “Ugba” was obtained by washing seeds at room temperature in 0.40% NaCl salt solution for 15 minutes. The supernatant was used for streaking on both Nutrient agar and “Ugba” agar plates and for Community DNA extraction. DNA extraction was carried out from community DNA extracts and culture isolates grown in LB (Luria – Bertani) broth at 37°C for 24 hours using Promega DNA extraction kit. Partial 16S rRNA genes of isolates DNA and entire microbial community DNA were amplified using 16S rRNA primers. Amplified fragments were cloned using the PCRTRAP. The transformed clones were sequenced and aligned with reference sequences in the NCBI data base for identification. Results: This analysis indicated that from community DNA, seventeen clones were identified as Bacillus subtilis, Nine as Bacillus pumilus, four as Bacillus licheniformis, two as Bacillaceae bacterium, two as Bacillus sp Van 22, and two as Staphylococcus spp. Also, of the ten sequenced cloned isolates from the cultural technique, eight were identified as Bacillus subtilis, while two sequences were identified as Bacillus pumilus. The percentage abundance revealed that Bacillus subtilis had the highest abundance of 47.2% followed by Bacillus pumilus with 25%. Conclusion: Bacillus subtilis is the predominant species in Ugba fermentation as it had high percentage abundance throughout the fermentation period. This study indicated that molecular analysis of community DNA provides a more accurate picture of diversity and dynamics of microbial communities.