Analysis of a Modern Hybrid and an Ancient Sugarcane Implicates a Complex Interplay of Factors in Affecting Recalcitrance to Cellulosic Ethanol Production

Abstract

Abundant evidence exists to support a role for lignin as an important element in biomass recalcitrance. However, several independent studies have also shown that factors apart from lignin are also relevant and overall, the relative importance of different recalcitrance traits remains in dispute. In this study we used two genetically distant sugarcane genotypes, and performed a correlational study with the variation in anatomical parameters, cell wall composition, and recalcitrance factors between these genotypes. In addition we also tracked alterations in these characteristics in internodes at different stages of development. Significant differences in the development of the culm between the genotypes were associated with clear differential distributions of lignin content and composition that were not correlated with saccharification and fermentation yield. Given the strong influence of the environment on lignin content and composition, we hypothesized that sampling within a single plant could allow us to more easily interpret recalcitrance and changes in lignin biosynthesis than analysing variations between different genotypes with extensive changes in plant morphology and culm anatomy. The syringyl/guaiacyl (S/G) ratio was higher in the oldest internode of the modern genotype, but S/G ratio was not correlated with enzymatic hydrolysis yield nor fermentation efficiency. Curiously we observed a strong positive correlation between ferulate ester level and cellulose conversion efficiency. Together, these data support the hypothesis that biomass enzymatic hydrolysis recalcitrance is governed by a quantitative heritage rather than a single trait.

Relationship between sugarcane culm and leaf biomass composition and saccharification efficiency

“…Furthermore, glucan conversion after pre-saccharification and SSF were significantly positively correlated ( r = 0.69). These results are consistent with the literature [62, 66, 81, 82] and indicate that ethanol yields are greatly dependent on the efficiency of saccharification. Therefore, improving saccharification efficiency by modifying the key characteristics identified in the path analysis should result in increased ethanol production from sugarcane biomass.…”

Fate of p-hydroxycinnamates and structural characteristics of residual hemicelluloses and lignin during alkaline-sulfite chemithermomechanical pretreatment of sugarcane bagasse

“…Characteristic signals from Cβ/Hβ correlations at δC/δH 113.5/6.27 were consistent with the esterified form of p CA in all bagasse samples, including the pretreated materials. The rest of the correlation signals observed in the spectra were also characteristic of p CA acylating the γ-OH in the lignin sidechain, as previously observed [ 18 , 38 ]. From these data, it is possible to conclude that a part of the ester bonds between p CA and γ-OH in the lignin sidechain were resistant to the highest alkaline-sulfite load used in the pretreatment.…”

Co-expression network analysis reveals transcription factors associated to cell wall biosynthesis in sugarcane

“…However, in intermediate internodes cell proliferation is much lower than compared to immature internodes, and cell expansion and elongation are the main processes taking place in this tissue. In fact, a recent work shows that in intermediate internodes of RB867515, parenchyma cells have higher diameter than cells in the same tissue of S. spontaneum (Guzzo de Carli Poelking et al 2015 ), suggesting a higher degree of cell expansion in the hybrid, which are also in agreement of differential expression of expansins, XTHs, and aquaporins. Still, this down regulation of histones in low Brixº plants needs to be further investigated to confirm any hypothesis.…”

“…Therefore, understanding and achieving control of lignification and lignin structure/composition is expected to be of great interest (Sticklen 2008 ). Despite all the information produced in plant models, specially Arabidopsis and poplar (Boerjan et al 2003 ; Bonawitz and Chapple 2010 ; Zhong and Ye 2009 ), only a few systematic studies have been carried out to address lignin metabolism in sugarcane (Bottcher et al 2013 ; Guzzo de Carli Poelking et al 2015 ; Vicentini et al 2015 ). In our results, despite the observed differences in growth and lignin contents (Table 1 ; Fig.…”