Waste Cassava Tuber Fibers as an Immobilization Carrier of Saccharomyces cerevisiae for Ethanol Production

Waste cassava tuber fibers (wCTF), derived from the ethanolic fermentation of cassava tubers, have potential use as anatural adsorption immobilization carrier. Ethanol fermentation was conducted using 15% (w/v) glucose-containing mediumat 40 °C for 48 h by Saccharomyces cerevisiae G6-2-2 (1.3 x 1010cells). Ethanol concentration produced by free, wCTF (1.2 g dry weight) adsorbed, wCTFadsorbed-calcium alginate entrapped,and calcium alginate entrapped cellswere 42.10 ± 0.61, 67.35 ± 0.53, 52.10 ± 0.40, and 46.45 ± 0.18 g/L (0.34, 0.45, 0.35, and 0.31 g ethanol/g reducing sugar), respectively. The wCTF adsorbed cells produced a maximum ethanol yield of 82.15 ± 0.48 g/L (0.43 g ethanol/g total sugar) from molasses (20% w/v initial total sugar) after 48 h, compared to 74 g/L to 76 g/L and 48 h to 100 h for the free suspension cells. The increase in ethanol produced by the wCTF adsorbed cells compared to free cells reflected that the cells were protected from environmental stresses and received amino nitrogen from the wCTF that supported growth and ethanol tolerance.