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New generation biofuel from whey: Successive acidogenesis and alcoholic fermentation using immobilized cultures on γ-alumina

Boura, Konstantina, Kandylis, Panagiotis, Bekatorou, Argyro, Kolliopoulos, Dionysios, Vasileiou, Dimitrios, Panas, Panayiotis, Kanellaki, Maria, Koutinas, Athanasios A.
Energy conversion and management 2017 v.135 pp. 256-260
alcoholic fermentation, aluminum oxide, biodiesel, biorefining, cheese whey, esterification, ethanol, kefir, lactic acid, lactose, upflow anaerobic sludge blanket reactor, whey
Cheese whey exploitation in a biorefinery manner is proposed involving anaerobic acidogenesis by a UASB mixed anaerobic culture and alcoholic fermentation by kefir. Both cultures were immobilized on γ-alumina. The produced organic acids (OAs) and ethanol could be esterified to obtain a novel ester-based biofuel similar to biodiesel. During acidogenesis, lactic acid-type fermentation occurred leading to 12gL⁻¹ total OAs and 0.2gL⁻¹ ethanol. The fermented substrate was subsequently supplied to a second bioreactor with immobilized kefir, which increased the OAs content (15gL⁻¹), especially lactic acid, and slightly the ethanol concentration (0.3–0.4gL⁻¹). To further increase ethanol concentration, a second experiment was conducted supplying whey firstly to the immobilized kefir bioreactor and then pumping the effluent into the acidogenesis bioreactor, resulting in 40% increase of OAs and 10-fold higher ethanol content. The residual sugar was ∼50% of the initial whey lactose; consequently, future research could result to further increase of ethanol and OAs.