Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae

Author(s):Show less -

Chandel, Anuj K. ^[1] ; Antunes, Felipe A. F. ^[1] ; Anjos, Virgilio ^[2] ; Bell, Maria J. V. ^[2] ; Rodrigues, Leonarde N. ^[2] ; Polikarpov, Igor ^[3] ; de Azevedo, Eduardo R. ^[3] ; Bernardinelli, Oigres D. ^[3] ; Rosa, Carlos A. ^[4] ; Pagnocca, Fernando C. ^[5] ; da Silva, Silvio S. ^[1]

Affiliation

^[1] Univ Sao Paulo, Sch Engn Lorena, Dept Biotechnol, BR-12602810 Lorena, SP - Brazil

^[2] Univ Fed Juiz de Fora, Dept Phys, Mat Spect Lab, BR-36036330 Juiz De Fora, MG - Brazil

^[3] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

^[4] Univ Fed Minas Gerais, Inst Ciencias Biol, Dept Microbiol, Belo Horizonte, MG - Brazil

^[5] CIES UNESP, Inst Biosci, Dept Biochem & Microbiol, Rio Claro, SP - Brazil

• Document type: Journal article
• Source: BIOTECHNOLOGY FOR BIOFUELS; v. 7, APR 16 2014.
• Web of Science Citations: 53

Abstract

Background: Heavy usage of gasoline, burgeoning fuel prices, and environmental issues have paved the way for the exploration of cellulosic ethanol. Cellulosic ethanol production technologies are emerging and require continued technological advancements. One of the most challenging issues is the pretreatment of lignocellulosic biomass for the desired sugars yields after enzymatic hydrolysis. We hypothesized that consecutive dilute sulfuric acid-dilute sodium hydroxide pretreatment would overcome the native recalcitrance of sugarcane bagasse (SB) by enhancing cellulase accessibility of the embedded cellulosic microfibrils. Results: SB hemicellulosic hydrolysate after concentration by vacuum evaporation and detoxification showed 30.89 g/l xylose along with other products (0.32 g/l glucose, 2.31 g/l arabinose, and 1.26 g/l acetic acid). The recovered cellulignin was subsequently delignified by sodium hydroxide mediated pretreatment. The acid-base pretreated material released 48.50 g/l total reducing sugars (0.91 g sugars/g cellulose amount in SB) after enzymatic hydrolysis. Ultra-structural mapping of acid-base pretreated and enzyme hydrolyzed SB by microscopic analysis (scanning electron microcopy (SEM), transmitted light microscopy (TLM), and spectroscopic analysis (X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Fourier transform near-infrared (FT-NIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy) elucidated the molecular changes in hemicellulose, cellulose, and lignin components of bagasse. The detoxified hemicellulosic hydrolysate was fermented by Scheffersomyces shehatae (syn. Candida shehatae UFMG HM 52.2) and resulted in 9.11 g/l ethanol production (yield 0.38 g/g) after 48 hours of fermentation. Enzymatic hydrolysate when fermented by Saccharomyces cerevisiae 174 revealed 8.13 g/l ethanol (yield 0.22 g/g) after 72 hours of fermentation. Conclusions: Multi-scale structural studies of SB after sequential acid-base pretreatment and enzymatic hydrolysis showed marked changes in hemicellulose and lignin removal at molecular level. The cellulosic material showed high saccharification efficiency after enzymatic hydrolysis. Hemicellulosic and cellulosic hydrolysates revealed moderate ethanol production by S. shehatae and S. cerevisiae under batch fermentation conditions. (AU)

• FAPESP's process: 08/57926-4 - Research and development aiming at the integrated exploitation of sugarcane bagasse for the biotechnological production of lignocellulosic ethanol
• Grantee: Silvio Silvério da Silva
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants