Continuous production of bioethanol from sugarcane bagasse and downstream purification using membrane integrated bioreactor

Bioethanol is the most widely used transportation fuel and is often employed as an alternate to conventional petroleum fuel. The most important challenge in bioethanol production process is to achieve nearly pure ethanol by downstream purification. Production of ethanol from sugarcane bagasse was studied in a membrane integrated hybrid bioreactor for 115 h using yeast strain Saccharomyces cerevisiae. The fermented product was subjected to continuous microfiltration after 20 h of batch fermentation and 100% rejection of microorganism was achieved at this state. A maximum cell density of 2.4 of was reached in the fermenter during fermentation. The maximum cell density reached in the fermenter during fermentation was 2.4 g/l. While studying the membrane performance during microfiltration, a flux decrease from 44.4 l/m2h to 8.4 l/m2h was observed after 65 h of continuous filtration at constant 3 bar transmembrane pressure. The permeate samples obtained from microfiltration were subjected to nanofiltration in order to recycle unconverted glucose from water ethanol mixture. During nanofiltration, the membrane performance revealed 58–86% rejection of glucose, a maximum ethanol concentration of 43.2 g/l in the permeate and the reduction of membrane flux from 41.4 l/m2h to 8.2 l/m2h after 19 h of continuous filtration at 10 bar transmembrane pressure. This membrane based approach for bioethanol production employs a sustainable and clean technology which comes up with low or no waste generation.