Immobilized Saccharomyces cerevisiae and Leuconostoc oenus for alcoholic and malolactic fermentation in continuous wine making

The use of sugarcane stalks to immobilize microorganisms by adsorption in continuous fermentation was investigated. The canes were peeled and cut horizontally and transversally into pieces 2 x 1 x 1 cm3. Scanning electron microscopy (SEM) was employed to verify the external and internal structure of the sugarcane stalk support prior to cell immobilization. The supports were used in a three-stage bioreactor system for continuous wine making and SEM was performed to verify immobilization of cells after 30 and 45 days of continuous fermentation. After one-week storage at 4°C another SEM analysis of the support was performed. The external and internal structure of the support showed a large number of immobilized cells and it appears that the presence of lignocellulosic material, which contains cellulose, hemicellulose, lignin, and protein, promoted biofilm formation, and that immobilization of the cells by adsorption is a time-dependent process.; A three-stage horizontal immobilized bioreactor system operating with Saccharomyces cerevisiae in the first stage and a mixed culture of S. cerevisiae and Leuconostoc oenus in the second and third stages was employed for continuous alcoholic and malolactic fermentation of a white grape juice from the cultivar Vidal Blanc. Flow-rate, dilution rate, and residence time were kept constant throughout the experiment and wine with an average of 10.08% ethanol by volume was produced during 45 days of continuous fermentation. Malolactic fermentation was monitored by measurements of pH increase, malic acid degradation and lactic acid formation. An average of 85% decrease in the total acidity was observed. A malic acid average of 0.08g/100 mL and lactic acid average of 0.31g/100 mL were determined during the period of continuous fermentation. A simple and rapid method for sample preparation for grape juice and wine analysis using high performance liquid chromatography (HPLC) with ultraviolet and refractive index detection was employed. The immobilized bioreactor system appeared to have potential for continuous winemaking.