The Algae That Eats Other Plants

A research team at Bielefeld University has made a groundbreaking discovery that one plant, the green alga Chlamydomonas reinhardtii, not only engages in photosynthesis, but also has an alternative source of energy: it can draw it out from other plants.

Plants need water and light to grow using sunlight energy to produce their biomass from earth, atmosphere and water.  Professor Dr. Olaf Kruse’s biological research team learned a breathtaking discovery; one plant has another way of doing this.  The news could have a major impact on the future of bioenergy.

The research team’s paper was published November 20 in the online journal Nature Communications.

Until now, it has been understood that only worms, bacteria, and fungi could digest vegetable cellulose and use it as a source of carbon for their growth and survival. In contrast plants engage in the photosynthesis of carbon dioxide, water, and light.

In a series of experiments, Professor Kruse and his team cultivated the microscopically small green alga species Chlamydomonas reinhardtii in a low carbon dioxide environment and observed that when faced with such a shortage, these single-cell plants can draw energy from neighboring vegetable cellulose instead.

The alga secretes enzymes (called cellulose enzymes) that ‘digest’ the cellulose, breaking it down into smaller sugar components. These are then transported into the cells and transformed into a source of energy: the alga can continue to grow.

Professor Kruse said, “This is the first time that such a behavior has been confirmed in a vegetable organism. That algae can digest cellulose contradicts every previous textbook. To a certain extent, what we are seeing is plants eating plants.”

Currently, the scientists are studying whether this mechanism can also be found in other types of alga. Preliminary findings indicate that this is the case.

This ‘new’ property of algae will be of interest for future bioenergy production. Breaking down vegetable cellulose biologically is one of the most important and unsatisfactory process tasks in the technology. Although vast quantities of waste containing cellulose are available from, for example, field crops, forestry, urban trash and other sources it cannot be transformed economically into biofuels in such forms.

Cellulose enzymes first have to break down the material and process it. Presently the necessary cellulose enzymes are extracted from fungi that, in turn, require organic material in order to grow.  If cellulose enzymes can be obtained from algae in the future there would be no more need for the organic material to feed the fungi. Then even when it is confirmed that algae can use alternative nutrients, water and light will suffice for them to grow in normal conditions.  No or much less CO2.

Suddenly the energy input for biomass processing looks very different – much less external to process power would be needed.  The prime competitor, the various pyrolysis processes could get a serious competition.  Much more of the biomass would go to fuel products.  Far more routes to fuels from biomass.

Its very early, we have just found out the opportunity is out there.  It will be interesting what the algae can teach us and show us about cracking down the cellulose and lignin.