Highly efficient, long life, reusable and robust photosynthetic hybrid core-shell beads for the sustainable production of high value compounds.

An efficient one-step process to synthesize highly porous (Ca-alginate-SiO2-polycation) shell: (Na-alginate-SiO2) core hybrid beads for cell encapsulation, yielding a reusable long-life photosynthetically active material for a sustainable manufacture of high-value metabolites is presented. Bead formation is based on crosslinking of an alginate biopolymer and mineralisation of silicic acid in combination with a coacervation process between a polycation and the silica sol, forming a semi-permeable external membrane. The excellent mechanical strength and durability of the monodispersed beads and the control of their porosity and textural properties is achieved by tailoring the silica and alginate loading, polycation concentration and incubation time during coacervation. This process has led to the formation of a remarkably robust hybrid material that confers exceptional protection to live cells against sheer stresses and contamination in a diverse range of applications. Dunaliella tertiolecta encapsulated within this hybrid core-shell system display high photosynthetic activity over a long duration (>1 year). This sustainable biotechnology could find use in high value chemical harvests and biofuel cells to photosynthetic solar cells (energy transformation, electricity production, water splitting technologies). Furthermore the material can be engineered into various forms from spheres to variable thickness films, broadening its potential applications.

Use of viability staining in combination with flow cytometry for rapid viability assessment of Lactobacillus rhamnosus GG in complex protein matrices.

The aim of this study was to demonstrate that flow cytometry (FACS) could potentially be employed for rapid viability assessment of probiotic bacteria immobilized or encapsulated in complex matrices. Lactobacillus rhamnosus GG was immobilized within six different protein environments using whey protein isolate (WPI) and yoghurt matrices and encapsulated within protein micro-beads, all of which ranged in structural complexity. Following a series of environmental-stress trials, survival of the strain was examined using FACS compared to traditional plate count techniques. Cell extraction and digestive pre-treatments were designed to release cells and reduce the protein background, respectively, which represent compositional obstacles for efficient FACS analysis. Physico-chemical properties of protein-probiotic components revealed the mechanism necessary for efficient cell delivery during FACS analysis. This assay required 40 min sample preparation and distinct functional populations were discriminated based on fluorescent properties of thiazole orange (TO) and propidium iodide (PI). This assay yielded 45-50 samples/h, a detection range of 10(2)-10(10)cfu/ml of homogenate and generated correlation coefficients (r) of 0.95, 0.92 and 0.93 in relation to standard plate counts during heat, acid and storage trials, respectively. In conclusion, this methodology provides impetus for dynamic progression of FACS for rapid viability assessment of live bacteria immobilized/encapsulated within complex protein systems.

Phycoremediation: key issues for cost-effective nutrient removal processes.

Phycoremediation applied to the removal of nutrients from animal wastewater and other high organic content wastewater is a field with a great potential and demand considering that surface and underground water bodies in several regions of the world are suffering of eutrophication. However, the development of more efficient nutrient removal algal systems requires further research in key areas. Algae growth rate controls directly and indirectly the nitrogen and phosphorus removal efficiency. Thus, maximum algae productivity is required for effective nutrient removal and must be considered as a key area of research. Likewise, low harvesting costs are also required for a cost-effective nutrient removal system. The use of filamentous microalgae with a high autoflocculation capacity and the use of immobilized cells have been investigated in this respect. Another key area of research is the use of algae strains with special attributes such as tolerance to extreme temperature, chemical composition with predominance of high added value products, a quick sedimentation behavior, or a capacity for growing mixotrophically. Finally, to combine most of the achievements from key areas and to design integrated recycling systems (IRS) should be an ultimate and rewarding goal.

Storage of immobilized yeast cells for use in wine-making at ambient temperature.

A comparative study of the storage and reuse of immobilized yeast cells on apple pieces, kissiris, and gamma-alumina was carried out. The immobilized biocatalysts were allowed to remain in the fermented alcoholic liquid after the end of each fermentation batch for extended periods at 30 degrees C before reactivation in batch fermentation for wine-making. The results showed that the biocatalysts were able to reactivate and ferment after successively increased periods of storage compared to free cell systems both on glucose medium and on grape must. In glucose medium, apple-, kissiris-, and gamma-alumina-supported biocatalysts reactivated after 120, 80, and 83 days, respectively. Possible storage periods for grape must were lower but remained high. Immobilized yeast biocatalyst on apple pieces produced wines with an improved volatiles composition compared to kissiris- and gamma-alumina-supported biocatalysts. There were no significant negative effects on the fermentation activity and volatile byproduct composition.