Exploitation of olive oil mill wastewaters and molasses for ethanol production using immobilized cells of Saccharomyces cerevisiae

An alcoholic fermentation process is described, involving molasses, the main by-product of the sugar industry, blended with crude olive oil mill wastewaters (OOMWs) and immobilized Saccharomyces cerevisiae cells on delignified cellulosic material (DCM). For comparison, fermentations with free cells were also carried out. Initially, the optimum blending mixture for molasses dilution was sought after, while at a second step repeated batch fermentations at a temperature range 5-30 degrees C were performed to monitor the operational stability of the system. A 1/1 ratio of OOMWs/tap water blending mixture and cell immobilization resulted in higher fermentation parameters. Ethanol concentration and daily productivity values recorded at temperatures >= 20 degrees C (up to 67.8 g L-1 and 67.6 g L-1 d(-1), respectively) could be adopted by the industrial sector, although the decline in fermentation efficiency observed, probably due to the toxicity effects of OOMWs. Finally, the potential of OOMWs treatment for ethanol production is highlighted and assessed.