Production of flavor-active compounds and physiological impacts in immobilized Saccharomyces spp. cells during beer fermentation.

Yeast immobilization in beer fermentation has recently regained attention, due to the expansion of the craft beer market and the diversification of styles and flavors. The aim of this study was to evaluate the physiological differences between immobilized and free yeast cells with a focus on flavor-active compounds formation. Three strains of Saccharomyces spp. (SY025, SY067, SY001) were evaluated in both free and immobilized (using a cellulose-based support, referred as ImoYeast) forms during static batch fermentations of 12 °P malt extract. Immobilized cells showed higher glycerol (SY025, 40%; SY067, 53%; SY001, 19%) and biomass (SY025, 67%; SY067, 78%; SY001, 56%) yields than free cells. Conversely, free cells presented higher ethanol yield (SY025, 9%; SY067, 9%; SY001, 13%). Flavor-active compounds production exhibited significant alterations between immobilized and free cells systems, for all strains tested. Finally, a central composite design with varying initial biomass (X0) and substrate (S0) concentrations was conducted using strain SY025, which can be helpful to modulate the formation of one or more flavor-active compounds. In conclusion, yeast immobilization in the evaluated support resulted in flavor alterations that can be exploited to produce different beer styles.

Rice vinasse treatment by immobilized Synechococcus pevalekii and its effect on Dunaliella salina cultivation.

The development of new strategies in microalgal studies represents an outstanding opportunity to mitigate environmental problems coupled with biomass production at a reduced cost. Here we present a combined bioprocess for the treatment of rice vinasse using immobilized cyanobacteria Synechococcus pevalekii in alginate beads followed by the use of the treated vinasse as a culture medium for Dunaliella salina biomass production. Cyanobacterial-alginate beads showed a chlorophyll a production of 0.68 × 10-3 mg bead-1 and a total carotenoid production of 0.64 × 10-3 mg bead-1. The first step showed a decrease in nitrate (91%), total solids (29%), and ions. Addition of treated vinasse into D. salina cultivation resulted in a significant increase in cell replication of about 175% (optimized cultivation). The use of natural seawater drastically reduced the medium cost to US$4.75 per m3 and the addition of treated vinasse has the potential to reduce it even more (up to 69%). This study not only provides an insight on the use of cyanobacteria for rice vinasse treatment but also demonstrates a promising lower-cost medium for marine microalgal biomass production with biotechnological purposes.