Bilal Ahmad Mir
The growing demand for energy and concerns about Greenhouse gas emissions have stimulated a worldwide interest in the exploitation of lignocellulosic plant biomass, the most abundant renewable and low-cost organic raw material for production of biofuels and biomaterials. In planta expression of lignocellulose digesting enzymes is a promising approach to reduce the production costs associated with biomass pretreatments and enzymatic hydrolysis. However, this approach faces a number of challenges, including auto-hydrolysis of developing cell walls, plant growth and yield penalties, low expression levels and the limited stability of expressed enzymes at the high temperatures generally used for biomass processing to release fermentable sugars. In planta consolidated bioprocessing using hyperthermophilic (HT) lignocellulose-degrading enzymes is a promising strategy for conversion of lignocellulose into fermentable sugars because these enzymes will continue to function during the ‘heat-up’ phase of a steam explosion process used for lignocellulose pretreatment. The high level functional expression of recombinant HT enzymes in bioenergy feedstocks could reduce, or even obviate, the need for exogenous enzyme additions prior to fermentation, substantially reducing the cost of the complete processing operation.