Altering the structure of lignin by engineering monolignol substitutes

In addition to engineering lignin structure by genes of the host plant itself (modification of H/G/S/benzodioxanes/aldehydes/ferulates), it might as well be possible to engineer easily degradable lignin polymers by using genes from other taxa in a synthetic biology approach, as discussed in Vanholme et al. (2012) and exemplified by Wilkerson et al. (2013). In this approach, the host plant is transformed with (a) heterologous gene(s) that encode(s) (a) biosynthetic enzyme(s) that is(are) able to make a monolignol substitute. When transported to the cell wall and incorporated into the lignin polymer, this molecule generates a bond that is more susceptible to the biomass pretreatment that is used to degrade the lignin polymer.