Lyophilization (Drying Method) Cause Serious Damages to the Cell Viability of Lactic Acid Bacteria

Preservation of industrial’s lactic acid bacteria (probiotics) by freeze-drying. Lactic acid bacteria have important nutritional needs and do not have resistance against the environmental conditions surrounding their production (drying, storage, etc.) and their use in vivo (physico-chemical properties of the digestive tract). In this condition, industrials and microbiologists develop regularly research projects of new lactic bacteria able to support the whole of the processes of production, storage and formulation without losing their functional properties. Among various methods of drying (atomization, fluidization and freeze-drying), freeze-drying makes it possible to obtain a thorough dehydration compatible with very long storage times. This method involves changes in product temperature and cause damage to microorganisms because it requires freezing that is not without consequences for cells. On the other side, it causes cellular (peroxydation of the fatty-acids) and genetic (proteins’s modifications) deteriorations. Using cryoprotectants and antioxidants during freeze-drying storage increases appreciably the rate of viability of these cells.

Electrostatic and Water Content Effects on Yarrowia lipolytica Lipase Immobilization by Adsorption.

Aims: In the present investigation, an attempt has been made to explain lipase immobilization by adsorption on three minerals matrixes, i.e. Celite 545, Silica gel (60G) and Avicel (PH 101). Study Design: immobilization by absorption on minerals matrixes, water content by volumetric karl Fischer titration and surface potentials using a particle charge detector Mutek PCD 03 were used. Place and Duration of Study: Walloon Centre of Industrial Biology (CWBI) Unit of Bio- Industries, University of Liege, Gembloux Agro-Bio Tech, Passage des Deportes 2, B- 5030 Gembloux, Belgium between Jun 2012 and jun 2013. Methodology: A methodical order was developed whereby the influences of water content, surface potentials and pH, on immobilization by adsorption were explored. Adsorbed YLL was used to understand an interesterification reaction between rapeseed oil and milk fat in comparison with a commercial silica-granulated Thermomyces lanuginosus lipase (Lipozyme TL IM). Results: Maximum immobilization yield was obtained with Celite (70%) and the lowest with silica gel (29%). Total water content of free and immobilized lipase was determined by volumetric Karl Fischer titration. The water content of Silica gel was higher than the one of other supports. Water content of silica gel could prevent the enzyme fixation. These results could be explained by the adsorption being governed mainly by electrostatic interactions between the enzyme and matrix. This hypothesis was further reinforced by measurements of electrical potential. They showed a lowest negative potential of Silica gel after enzyme adsorption in comparison to Celite. Conclusion: From these results celite was designated as an efficient matrix to immobilize Yarrowia lipolytica lipase (YLL) by adsorption. This performed system was used to realize an interesterification reaction between rapeseed oil and milk fat in comparison with a commercial silica-granulated Thermomyces lanuginosus lipase (Lipozyme TL IM).