Bioethanol production from cassava fermentation in pervaporation membrane bioreactor fed with high concentration sugar

Bioethanol production from cassava in a pervaporation membrane bioreactor consisted of fermentation coupled with polydimethylsiloxane (PDMS) membrane separation has been carried out. A cassava hydrolysate with a high sugar concentration of 448-492 gL-1 was prepared by repeating the liquefaction process and then fed to the bioreactor to overcome the fermentation broth volume expansion problem. The coupled system lasted as long as 248 h. The cell concentration, sugar consumption rate, ethanol productivity, and total ethanol production were 22 gL-1, 3.91 gL-1h-1, 1.47 gL-1h-1, and 365.1 gL-1, respectively. The average membrane flux and separation factors of the membrane were 645 gm -2h-1 and 5.3, respectively. A permeate vapor with as high as 21.5 wt% ethanol concentration downstream of the membrane was obtained. Fractional condensation was used downstream of the membrane to differentially refine and recover the ethanol from the permeate vapor. The ethanol concentration can be increased by 57.3 % with the fractional condensation method, with separation factor increased to 9.8-14.9. As much as 96.6 % of the permeated ethanol on the downstream of the membrane can be recovered as the product with high ethanol concentration.