Alkaline-sulfite pretreatment and use of surfactants during enzymatic hydrolysis to enhance ethanol production from sugarcane bagasse

• Published in: Bioprocess and biosystems engineering Vol. 39; no. 3; pp. 441 - 448
• Main Authors: Mesquita, Jéssica Faria, Ferraz, André, Aguiar, André
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-03-2016; Springer Nature B.V
• Subjects: Bagasse; Biotechnology; Cellulose - chemistry; Chemistry; Chemistry and Materials Science; Environmental Engineering/Biotechnology; enzymatic hydrolysis; Enzymes; Ethanol; ethanol fuels; ethanol production; Fermentation; Food Science; glucose; Hydrolysis; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; industry; lignin; Original Paper; polysaccharides; polysorbates; raw materials; Saccharides; Saccharum - chemistry; Sodium hydroxide; Sodium Hydroxide - chemistry; Sugarcane; sugarcane bagasse; Sulfites - chemistry; Surface-Active Agents - chemistry; Surfactants; Tween 20; Lignin; Ethanol; Semi-simultaneous hydrolysis and fermentation; Cellulose
• ISSN: 1615-7591; 1615-7605
• DOI: 10.1007/s00449-015-1527-z

Sugarcane bagasse is a by-product from the sugar and ethanol industry which contains approximately 70 % of its dry mass composed by polysaccharides. To convert these polysaccharides into fuel ethanol it is necessary a pretreatment step to increase the enzymatic digestibility of the recalcitrant raw material. In this work, sugarcane bagasse was pretreated by an alkaline-sulfite chemithermomechanical process for increasing its enzymatic digestibility. Na₂SO₃ and NaOH ratios were fixed at 2:1, and three increasing chemical loads, varying from 4 to 8 % m/m Na₂SO₃, were used to prepare the pretreated materials. The increase in the alkaline-sulfite load decreased the lignin content in the pretreated material up to 35.5 % at the highest chemical load. The pretreated samples presented enhanced glucose yields during enzymatic hydrolysis as a function of the pretreatment severity. The maximum glucose yield (64 %) was observed for the samples pretreated with the highest chemical load. The use of 2.5 g l⁻¹ Tween 20 in the hydrolysis step further increased the glucose yield to 75 %. Semi-simultaneous hydrolysis and fermentation of the pretreated materials indicated that the ethanol yield was also enhanced as a function of the pretreatment severity. The maximum ethanol yield was 56 ± 2 % for the sample pretreated with the highest chemical load. For the sample pretreated with the lowest chemical load (2 % m/m NaOH and 4 % m/m Na₂SO₃), adding Tween 20 during the hydrolysis process increased the ethanol yield from 25 ± 3 to 39.5 ± 1 %.