Chemical Pulping Advantages of Zip‐lignin Hybrid Poplar

Abstract

Hybrid poplar genetically engineered to possess chemically labile ester linkages in its lignin backbone (zip‐lignin hybrid poplar) was examined to determine if the strategic lignin modifications would enhance chemical pulping efficiencies. Kraft pulping of zip‐lignin and wild‐type hybrid poplar was performed in lab‐scale reactors under conditions of varying severity by altering time, temperature and chemical charge. The resulting pulps were analyzed for yield, residual lignin content, and cellulose DP (degree of polymerization), as well as changes in carbohydrates and lignin structure. Statistical models of pulping were created, and the pulp bleaching and physical properties evaluated. Under identical cooking conditions, compared to wild‐type, the zip‐lignin hybrid poplar showed extended delignification, confirming the zip‐lignin effect. Additionally, yield and carbohydrate content of the ensuing pulps were slightly elevated, as was the cellulose DP for zip‐lignin poplar pulp, although differences in residual lignin between zip‐lignin and wild‐type poplar were not detected. Statistical prediction models facilitated comparisons between pulping conditions that resulted in identical delignification, with the zip‐lignin poplar needing milder cooking conditions and resulting in higher pulp yield (up to 1.41 % gain). Bleaching and physical properties were subsequently equivalent between the samples with slight chemical savings realized in the zip‐lignin samples due to the enhanced delignification.

Reductive Cleavage Method for Quantitation of Monolignols and Low‐Abundance Monolignol Conjugates

“…DFRC offers several features: it selectively cleaves β‐ether bonds while retaining ester linkages, thus providing conclusive evidence of monolignol conjugate incorporation into lignins; a final acetylation step simplifies data interpretation by reducing the number of analytes; and two modified versions of the protocol use common reagents to distinguish between freephenolic and etherified units in the polymer, as well as natural γ‐acetates and those introduced by the method itself (Scheme ). In recent years, DFRC has been an indispensable tool in confirming the incorporation of monolignol acetate (Ac), p ‐coumarate ( p CA), benzoate (BA), p ‐hydroxybenzoate ( p BA), vanillate (VA), and ferulate (FA) conjugates into the lignin polymer.…”

Identification of enzymatic genes with the potential to reduce biomass recalcitrance through lignin manipulation in Arabidopsis

“…Recently, Wilkerson et al expressed a gene encoding feruloyl-CoA monolignol transferase, which was isolated from Chinese angelica, in poplar and successfully increased incorporation of acylated monolignols into lignin [13]. After pretreatment with mild alkali or ionic liquid, significant improvements in saccharification rate and chemical pulping yield are evident in plants harboring the gene [14,15]. Simultaneous expression of diketide-CoA synthase and curcumin synthase 2 originating from turmeric (Curcuma longa) also rerouted the monolignol biosynthetic pathway in transgenic Arabidopsis plants for heterologous production of curcumin [16].…”

Strategies for Engineering Reproductive Sterility in Plantation Forests

“…Genetic engineering (GE) is able to provide solutions for many of the challenges forestry faces to sustainably increase forest production. Improved wood quantity and quality, processability, biotic, and abiotic stress tolerance and herbicide tolerance ( Harfouche et al, 2011 ; Porth and El-Kassaby, 2014 ; Etchells et al, 2015 ; Ault et al, 2016 ; Zhou et al, 2017 ) are amongst the traits successfully demonstrated. The recent approval by the Brazilian Regulator for GE Eucalyptus that are able to grow 15–20% faster than the best existing clonal lines ( Nature Biotechnology News, 2015 ) seems likely to lead to first large-scale commercial planting of trees.…”