Effects of enzymatic removal of plant cell wall acylation (acetylation, p-coumaroylation, and feruloylation) on accessibility of cellulose and xylan in natural (non-pretreated) sugar cane fractions

Author(s)

Varnai, Aniko ^{[1, 2, 3]} ; Costa, Thales H. F. ^[4] ; Faulds, Craig B. ^{[5, 6]} ; Milagres, Adriane M. F. ^[4] ; Siika-aho, Matti ^[1] ; Ferraz, Andre ^[4]

Affiliation

^[1] VTT Tech Res Ctr Finland, Espoo 02044 - Finland

^[2] Norwegian Univ Life Sci, Dept Chem Biotechnol & Food Sci, N-1432 As - Norway

^[3] Univ Helsinki, Dept Food & Environm Sci, FIN-00014 Helsinki - Finland

^[4] Univ Sao Paulo, Dept Biotechnol, Escola Engn Lorena, BR-12602810 Lorena, SP - Brazil

^[5] Aix Marseille Univ, POLYTECH, INRA, UMR Biodivers & Biotechnol Fong BBF 1163, F-13288 Marseille 09 - France

^[6] Aix Marseille Univ, INRA, BBF, UMR A 1163, F-13288 Marseille 09 - France

• Document type: Journal article
• Source: BIOTECHNOLOGY FOR BIOFUELS; v. 7, OCT 15 2014.
• Web of Science Citations: 17

Abstract

Background: Sugar cane internodes can be divided diagonally into four fractions, of which the two innermost ones are the least recalcitrant pith and the moderately accessible pith-rind interface. These fractions differ in enzymatic hydrolyzability due to structural differences. In general, cellulose hydrolysis in plants is hindered by its physical interaction with hemicellulose and lignin. Lignin is believed to be linked covalently to hemicellulose through hydroxycinnamic acids, forming a compact matrix around the polysaccharides. Acetyl xylan esterase and three feruloyl esterases were evaluated for their potential to fragment the lignocellulosic network in sugar cane and to indirectly increase the accessibility of cellulose. Results: The hydrolyzability of the pith and pith-rind interface fractions of a low-lignin-containing sugar cane clone (H58) was compared to that of a reference cultivar (RC). Acetyl xylan esterase enhanced the rate and overall yield of cellulose and xylan hydrolysis in all four substrates. Of the three feruloyl esterases tested, only TsFaeC was capable of releasing p-coumaric acid, while AnFaeA and NcFaeD released ferulic acid from both the pith and interface fractions. Ferulic acid release was higher from the less recalcitrant clone (H58)/fraction (pith), whereas more p-coumaric acid was released from the clone (RC)/fraction (interface) with a higher lignin content. In addition, a compositional analysis of the four fractions revealed that p-coumaroyl content correlated with lignin, while feruloyl content correlated with arabinose content, suggesting different esterification patterns of these two hydroxycinnamic acids. Despite the extensive release of phenolic acids, feruloyl esterases only moderately promoted enzyme access to cellulose or xylan. Conclusions: Acetyl xylan esterase TrAXE was more efficient in enhancing the overall saccharification of sugar cane, compared to the feruloyl esterases AnFaeA, TsFaeC, and NcFaeD. The hydroxycinnamic acid composition of sugar cane fractions and the hydrolysis data together suggest that feruloyl groups are more likely to decorate xylan, while p-coumaroyl groups are rather linked to lignin. The three different feruloyl esterases had distinct product profiles on non-pretreated sugar cane substrate, indicating that sugar cane pith could function as a possible natural substrate for feruloyl esterase activity measurements. Hydrolysis data suggest that TsFaeC was able to release p-coumaroyl groups esterifying lignin. (AU)

• FAPESP's process: 11/50535-2 - Microspectrophotometry applied to the study of lignocellulose recalcitrance
• Grantee: Andre Luis Ferraz
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/56256-5 - Topochemistry, porosity and chemical composition determining successful enzymatic sacarification of sugarcane bagasse
• Grantee: Adriane Maria Ferreira Milagres
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants