Plant cell wall degrading enzymes of the parasitic plant Cuscuta as new tools in
biofuels production
Hanne Risan Johnsen, Kirsten Krause
Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics,
University of Tromsø
Project Summary
The concept described here is based on a PhD project whose primary goal is to characterize cell wall
degrading enzyme activities of the parasitic plant genus Cuscuta. Due to their proven high activity,
such enzymes that are produced during the infection of host plants can be used to improve biofuel
production from agricultural waste products and overcome some of the current problems of biomass
recalcitrance.
Background
The production of economically viable biofuels plays an important role in the current and future
management of energy resources. Biofuels can contribute to addressing some of the problems connected to
climate change. With a growing biofuels industry that serves the private as well as the industrial sector, the
global challenge is to develop novel approaches to sustainably utilise available biomasses.
The two main approaches for obtaining biofuels are currently fermentation of food crops and extraction of
burnable oil from oil-rich plants. In the face of extensive famine in some parts of the world, the conversion
of edible plant parts into biofuels is, however, a highly controversial subject. The production of ethanol from
non-edible plant parts would solve this controversy. Unfortunately, the difficulty of processing or degrading
cellulosic biomass to fermentable substances has so far prevented the development of a successful cellulosic
biofuel industry.
Parasitic plants have perfected the strategy to penetrate lignified and unlignified plant tissue in order to
“steal” nutrients from their host plants (Figure 1). They use hydrolytic enzymes to break down the cell walls
of different hosts very effectively and send extensions of their own tissue deep into the host tissue (Fig. 1C).
Although they are very promising candidates for bioprospecting of novel degrading enzyme activities,
parasitic plants have so far not been included in respective screening attempts and therefore represent an
entirely unexploited resource for the cellulosic biofuels industry.
Figure 1: (A) Parasitic plant (here: Cuscuta gronovii) winding
around its host plant. (B) Detailed view of (A) showing the
penetrating organs (arrows). (C) Cross section showing
penetration of host tissue by Cuscuta (arrow). During this
penetration process hydrolytic enzymes are excreted, that
dissolve the host plant cell walls.
Our project aims at isolating the relevant enzymes from Cuscuta species using a variety of molecular and
biochemical approaches and developing novel enzyme cocktails that are suitable for biofuel production.
The prize money would be used to cover costs for the participation in international conferences on biofuel
production and alternative energy sources as well as parasitic plant biology. In addition, it would be used to
visit one foreign lab whose competence and methods spectrum could broaden the projects perspective.
Specifically, a group with expertise on computational protein modelling would be of high interest, as the
identified enzymes could be even further improved using modelling predictions.