Sustainable Second-Generation Ethanol Production from Switchgrass Biomass via Co-fermentation of Pentoses and Hexoses Using Novel Wild Yeasts

Author(s)

Antunes, Felipe Antonio Fernandes ^[1] ; Rajan, Kalavathy ^[2] ; Djioleu, Angele ^[3] ; Rocha, Thiago Moura ^[1] ; Brumano, Larissa Pereira ^[1] ; de Souza Melo, Yasmin Cristhine ^[1] ; dos Santos, Julio Cesar ^[1] ; Rosa, Carlos A. ^[4] ; Carrier, Danielle Julie ^[2] ; da Silva, Silvio Silverio ^[1]

Affiliation

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

^[2] Univ Tennessee, Dept Biosyst Engn & Soil Sci, 2506 EJ Chapman Dr, Knoxville, TN 37996 - USA

^[3] Univ Arkansas, Dept Biol & Agr Engn, 203 White Engn Hall, Fayetteville, AR 72701 - USA

^[4] Univ Fed Minas Gerais, Inst Biol Sci, Av Pres Antonio Carlos, BR-66273127 Pampulha, MG - Brazil

• Document type: Journal article
• Source: BioEnergy Research; JUL 2021.
• Web of Science Citations: 0

Abstract

The production of second-generation (2G) ethanol remains an interesting proposition for the implementation of sustainable and net carbon-neutral energy systems. To be economically viable, 2G biorefineries must make use of all processing streams, including the less desirable pentose (C5) sugar stream. In this work, a strategy of sequential dilute acid and alkaline pretreatment of the lignocellulosic feedstock, switchgrass, was implemented for improving the fermentable sugar yield. The hemicellulose-enriched hydrolysate obtained after dilute acid pretreatment was fermented by a newly isolated wild Scheffersomyces parashehatae strain-UFMG-HM-60.1b; the corresponding ethanol yield (Y-PS) and volumetric productivity (Q(P)) were 0.19 g/g and 0.16 g/L h, respectively. The remaining switchgrass cellulignin fraction was subjected to optimized alkaline delignification at 152 oC for 30 min. Then, the delignified solid fraction was subjected to contiguous enzymatic saccharification and fermentation releasing a glucose (C6) sugar stream. The control yeast strain, Saccharomyces cerevisiae 174, displayed an ethanol Y-PS of 0.46 g/g and Q(P) of 0.70 g/L h for the C6 sugar stream, whereas the above-mentioned wild strain presented Y-PS and Q(P) of 0.29 g/g and 0.38 g/L h, respectively. Upon combining the conversion of hemicellulose (37%) and cellulose-derived sugars (57%), the wild S. parashehatae strain provided higher yield (94%) than the generic S. cerevisiae (90%). Henceforth, our sequential two-stage pretreatment and fermentation of C5 and C6 sugar streams provides a pathway for maximum utilization of switchgrass carbohydrates for 2G ethanol production. (AU)

• FAPESP's process: 16/10636-8 - From the cell factory to the Biodiesel-Bioethanol integrated biorefinery: a systems approach applied to complex problems in micro and macroscales
• Grantee: Roberto de Campos Giordano
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants
• FAPESP's process: 14/27055-2 - Processes intensification of lignocellulosic biorefineries integrating ethanol and xylitol production steps from sugarcane bagasse in fluidized bed bioreactor
• Grantee: Felipe Antonio Fernandes Antunes
• Support Opportunities: Scholarships in Brazil - Post-Doctoral