Singh P., Medronho B.2, Miguel M.G.1,3,4, Lindman B. 1,3,4,5
1 Department of Chemistry, University of Coimbra, Portugal

2 Faculty of Sciences and Technology, University of Algarve, Portugal

3 Division of Physical Chemistry, Lund University, Sweden

4 Materials Science and Engineering, Nanyang Technological University, Singapore

5 FSCN, Mid Sweden University, Sweden

Cellulose is abundantly found in nature with unique properties such as biocompatibility and biodegradability. As an amphiphilic polysaccharide it can be used to form hydrogels which may undergo swelling or de-swelling depending on media conditions. Among vast range of possible systems to be encapsulated and delivered, probiotics emerge as a very interesting class receiving a lot of attention nowadays. This study is based on development and characterization of cellulose based hydrogels and encapsulation of probiotic bacteria.

Three different cellulose derivatives with positive modified HEC (SoftCAT Polymer SK-M, da Amerchol, lote: TC2550GRA1), negative sodium CMC (Mw 70,000 Sigma Aldrich) and no charge HPMC (2,600-5,600 mPa.s, 2 % in H2O) were selected in combination of different polysaccharides. Chitosan (20-300 cP, 1 wt. % in 1% acetic acid) was studied cross linking with genipin.
Systems were characterized by rheology using a HAAKE MARS III rheometer (Thermo Fisher Scientific, Germany) controlling the temperature (at 25 and 37 ºC). Swelling Analysis using fresh sample, freeze dried and oven dried in a neutral aqueous solution and continuous readings were taken every five minutes.
Cryo-scanning electron microscopy (Cryo-SEM) was carried out using a JEOL JSM-6301F (Tokyo, Japan), Oxford Instruments INCA Energy 350 (Abingdon, UK.)
Thermogravimetric analyses (TGA) of pure samples and composite gel membranes, prepared with different amounts were carried out on thermo-microbalance thermogravimetric analyzer TG 209 F3 Tarsus®.
Lactobacillus rhamnosus GG (LMG 18243) was revived by inoculating in MRS media at 37`C for 2 days in a CO2 incubator. The most promising hydrogels were dried in oven for 10 hours at 60`C. 1 mg of dried gel was soaked in bacterial cultured media for 30 minutes, after that serial dilution was performed on MRS Agar media using spread plate method. The plates were further incubated in anaerobic conditions for 48 hours for viability count. Analysis through Fluorescence microscope (Olympus BX51M microscope) was performed.

Several phase diagrams were developed for physical gels but essentially it was found that most of the systems formed stiff hydrogels at high concentration of polymers. After freeze drying, the systems showed the maximum swelling. Moreover, it was found that different cellulose derivatives showed almost the same degradation temperature in the TGA analysis. For the chemical gels the addition of genipin demonstrated high efficiency in cross-linking the chitosan based systems. Viability: The hydrogels showed a promising results using diffusion method as the viability of bacteria counted was in the limit mentioned by the regulations to be effective in the gut.

Development of encapsulation matrix is not an easy task. Most of the probiotics products in the market are based on dairy; this encapsulation strategy will open new choice of food products to opt for.

Keywords: Cellulose, Rhamnosus GG, Hydrogels, Probiotic, Characterization, Delivery

Singh P., et al. (2016). Characterization of cellulose based hydrogels as probiotics delivery vehicles. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 70.). IPC2016

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