Engineering Cell Wall-Degrading Enzymes into Growing Plants to Improve Lignocellulosic Ethanol Production

The plant cell wall (PCW) represents the most abundant renewable biomass resource for lignocellulosic ethanol production. Economical and efficient degradation of PCW to fermentable sugars is an essential sub-process during lignocellulosic ethanol production. At present, the recalcitrance of PCW to various pretreatments and enzymatic hydrolysis makes the PCW degradation unacceptably expensive. Engineering cell wall-degrading enzymes into growing plants provides a promising solution to lower the PCW degradation cost and increase its degradation efficiency for lignocellulosic ethanol production. Avoiding damage by the expressed biomass-degrading enzymes to growing plants is the key to successful use of this method. Two modern biological technologies can be used to solve this problem. One is to engineer a thermoregulated intein-modified cell wall-degrading enzyme into growing plants. The other is to use the gene-timed expression technique. This editorial will give a brief discussion of opportunities and challenges of engineering cell wall-degrading enzymes into growing plants for improvement of lignocellulosic ethanol production.