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Engineering Competitive Pathways for Tissue-Specific Lignin Reduction


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Berkeley Lab researchers Dominique Loqué and Aymerick Eudes have developed a set of genetic engineering technologies for tissue-specific reduction of lignin, the woody material in plants that can make them unsuitable feedstocks for biofuels.

The Berkeley Lab team determined that lignin in vessel tissue is essential for plant development and growth, but it is far less important in fiber cells. Therefore, they created a series of dominant strategies that use specific promoters to reduce lignin only in specific cell types, such as those that make up secondary cell walls. Their approach employs competitive pathways that deplete metabolites from the monolignol / lignin biosynthesis pathway. The result is lower lignin levels in plants (up to 50% less) without significant reduction in biomass yield, and consequently a major increase in saccharification efficiency and biomass digestibility (>2.5 fold increase after hot-water pretreatment).

Biofuels derived from lignocellulosic biomass are promising alternatives to fossil fuels. However, plants are notoriously resistant to enzymatic digestion processes that reduce them into simple sugars that can then be converted into fuels. This recalcitrance is mainly caused by polysaccharide polymers embedded in lignin. They are difficult to extract and block access to the hydrolytic enzymes needed to digest raw biomass.

Currently, the most common approach to reducing lignin has been to use lignin gene-silencing techniques or mutant screening. These techniques are not cell-specific, so they reduce lignin biosynthesis in all plant tissues, lowering biomass yield and increasing vulnerability to pathogens. The Berkeley Lab strategy optimizes lignin reduction only in tissues that do not need lignin. The method optimizes the breakdown of complex carbohydrates into simple sugars without adversely affecting plant growth and development, or pathogen resistance. It has the added benefit of reducing the amount of lignin waste that accumulates during the biological conversion of lignocellulosic biomass into biofuels.

DEVELOPMENT STAGE:  Proven principle
STATUS:  Patent pending.  Available for licensing or collaborative research.




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