Hemicellulosic ethanol production by immobilized cells of Scheffersomyces stipitis: Effect of cell concentration and stirring

Abstract

Bioconversion of hemicellulosic hydrolysate into ethanol plays a pivotal role in the overall success of biorefineries. For the efficient fermentative conversion of hemicellulosic hydrolysates into ethanol, the use of immobilized cells system could provide the enhanced ethanol productivities with significant time savings. Here, we investigated the effect of 2 important factors (e.g., cell concentration and stirring) on ethanol production from sugarcane bagasse hydrolysate using the yeast Scheffersomyces stipitis immobilized in calcium alginate matrix. A 2² full factorial design of experiment was performed considering the process variables- immobilized cell concentration (3.0, 6.5 and 10.0 g/L) and stirring (100, 200 and 300 rpm). Statistical analysis showed that stirring has the major influence on ethanol production. Maximum ethanol production (8.90 g/l) with ethanol yield (Yp/s) of 0.33 g/g and ethanol productivity (Qp) of 0.185 g/l/h was obtained under the optimized process conditions (10.0 g/L of cells and 100 rpm).

Keywords:

• bioethanol
• cell immobilization
• dilute acid hydrolysis
• Scheffersomyces stipitis
• sugarcane bagasse hydrolysate

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Funding

Authors thank to Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP–BIOEN Project grants: 2008/57926–4 and 2010/13828–9), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the financial support.