Consolidated processing of transgenic corn stover expressing cell wall degrading enzymes using a low severity pretreatment

One key to the success of a biorefinery is to obtain the lowest cost sugars for conversion into other bioproducts. In order to generate low cost sugars for processing, the high cost of biomass pretreatment and enzyme hydrolysis must be reduced. To address these cost barriers of cellulosic processing, Agrivida Inc has developed technologies to engineer a portfolio of cell wall degrading (CWD) enzymes into biomass plants. Significant enzyme accumulation enables us to reduce pretreatment severity, increase saccharification efficiency, and reduce external enzyme loadings, which provides a low-cost sugar platform for large markets. To efficiently process the transgenic plants, a moderate pretreatment system was developed to achieve pretreatment effects on the biomass cell wall without deactivating the hydrolytic enzymes within plant. This pretreatment was conducted at a temperature lower than 90 ⁰C and a pH in the range of 4.0-9.0, involving auto-enzymatic hydrolysis, and moderate chemi-mechanical pretreatment, resulting in no or little toxic products. After pretreatment, the slurry was subjected to direct enzymatic hydrolysis after pH adjustment without inter-stage washing and separation.  The study for the enzymatic hydrolysis of the pretreated transgenic corn stover demonstrate that 80-88% glucan and over 70% xylan hydrolysis can be achieved for a 3-day enzymatic hydrolysis with 20% full loading (0.1-0.2 mL/g biomass) of commercial enzyme cocktails, over 50% higher glucan hydrolysis than the negative control corn stover under similar processing conditions, demonstrating the potential of  reducing both pretreatment and enzyme costs in cellulosic bioprocessing by the production of enzymes in plants.