Silica-alginate-encapsulated bacteria to enhance malolactic fermentation performance in a stressful environment

Abstract

Background and Aims Beginning and completion of malolactic fermentation (MLF) are complicated because of the harsh environment of wine. Encapsulation of lactic acid bacteria could be an attractive strategy to improve their activity and stability. This work evaluates the fermentative capacity of Oenococcus oeni encapsulated into silica–alginate (Si–Al) and alginate capsules under adverse winemaking conditions (high alcohol concentration, low pH and low temperature). Mechanical and chemical stability of capsules was also monitored. Methods and Results Silica–alginate capsules showed higher malolactic activity and better mechanical and chemical stability than untreated alginate capsules. Their capacity for bacteria retention was similar to that of alginate capsules. Ethanol, pH and fermentation temperature had great influence on fermentative behaviour of free and encapsulated bacteria. Under extreme winemaking conditions, such as high ethanol concentration (13–16%), low pH (3.0–3.3) and low fermentation temperature (13–15°C), the highest consumption of malic acid was achieved using Si–Al capsules. Free and encapsulated bacteria showed similar fermentative profiles in the presence of variable concentration of malic acid and nitrogen in wine. Conclusions Encapsulated O. oeni in Si–Al gels enhanced MLF in wines with a high concentration of ethanol and low pH and at low fermentation temperature. Moreover, inclusion of an inorganic network of silicates significantly improved the mechanical robustness and chemical stability of alginate capsules. Significance of the Study The application of Si–Al-encapsulated bacteria is an interesting strategy to improve MLF in warm climates where wines have higher ethanol concentration and in cool climates with higher acidity and low fermentation temperature.