Ethanol production from high solid loading of rice straw by simultaneous saccharification and fermentation in a non-conventional reactor

Inês C. Roberto, Rafael C.A. Castro, João Paulo A. Silva, Solange I. Mussatto*

*Corresponding author for this work

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Abstract

Simultaneous saccharification and fermentation (SSF) at high solid loading is a potential approach to improve the economic feasibility of cellulosic ethanol. In this study, SSF using high loading of rice straw was assessed using a vertical ball mill reactor. First, the conditions of temperature and number of glass spheres were optimized at 8% (w/v) initial solids (41.5 °C, 18 spheres). Then, assays were carried out at higher solid loadings (16% and 24% w/v). At 8% or 16% solids, the fermentation efficiency was similar (ηF~75%), but the ethanol volumetric productivity (QP) reduced from 1.50 to 1.14 g/L.h. By increasing the solids to 24%, the process was strongly affected (ηF = 40% and QP = 0.7 g/L.h). To overcome this drawback, three different feeding profiles of 24% pre-treated rice straw were investigated. Gradual feeding of the substrate (initial load of 16% with additions of 4% at 10 and 24 h) and an inoculum level of 3 g/L resulted in a high ethanol titer (52.3 g/L) with QP of 1.1 g/L.h and ηF of 67%. These findings demonstrated that using a suitable fed-batch feeding strategy helps to overcome the limitations of SSF in batch mode caused by the use of high solid content.
Original languageEnglish
Article number2090
JournalEnergies
Volume13
Issue number8
Number of pages17
ISSN1996-1073
DOIs
Publication statusPublished - 2020

Keywords

  • Ethanol
  • Simultaneous saccharification and fermentation
  • Rice straw
  • Vertical ball mill reactor
  • Kluyveromyces marxianus

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