Bioenergy and high value products from microalgae

Contact: Giuseppe Torzillo (Unit of Firenze)
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Microalgae have attracted commercial interest for their potential capacity to synthesize valuable products since 1950 (Burley 1952). In Fig. 1 are shown the basic concept of algal biotechnology, pointing out the basic inputs and potential outputs and products that can be obtained from the algal biomass. In view of the variety of valuable compounds produced by microalgae species and their wide physiological and functional diversity, it can be expected that microalgae cultures could play an important role in the future as ‘cell-factories’.

Task 1. Microalgae as a source of bio-energy

Producing bio energy (biohydrogen and biodiesel) from algae is nowadays widely believed as one possible alternative for the development of CO2-neutral fuels for several reasons 1) microalgae have a higher photon conversion efficiency which is translated in a higher biomass yield per unit of surface; they can: a) synthesize and accumulate large quantity of neutral lipids (TAGs); b) release hydrogen under specific growth conditions; c) utilize growth nutrients such as nitrogen and phosphorous from a variety of wastewater sources, providing additional benefit of wastewater bioremediation.

One friendly way of producing energy is photobiological H2 production using the microalga Chlamydomonas reinhardtii. A number of D1 protein mutants has been screened in our laboratory for their H2 evolution capacity. Some of them have proved to be up to 5 times more productive as compared to the cc124 strain, the strain commonly utilized for hydrogen experiments worldwide [1]. A phenotypic characterization has identified some important common features, such as: (i) a reduced antenna size (i.e., a reduced amount of chlorophyll per cell), (ii) high respiration photosynthesis ratio, (iii) high carbohydrate accumulation, and (iv) higher D1 protein content per cell [2]. We have also investigated the possibility of using wastewaters rich in organic acids and sugars, as a substrate on which to grow Chlamydomonas, in order to obtain suitable biomass to produce hydrogen [3]. These cultures were found to be richer in carbohydrates and exhibited a greater production of hydrogen (150 ml H2 l-1 culture), compared to the control cells (100 ml H2 l-1 culture).

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Research

  1. Selection of Chlamydomonas reinhardtii strains with high hydrogen output rate
  2. Selection of microalgal strains with high lipid content
  3. Optimization of the cultures conditions in laboratory photobioreactors.
  4. Testing hydrogen production in photobioreactors outdoors
  5. Developing a cost-effective photobioreactor design for hydrogen and biodiesel production

Task 2. Microalgae as a source of high value substances

Microalgae can act as green cell-factories for the manufacture of high added-value, specially products with straightforward applicability and increasing market demand- and via processes that are environment-friendly and essentially safe. Nevertheless, several bottlenecks preclude their feasible industrial exploitation at present; most wild microalgae remain unscreened for bioactive compounds.

Research

  1. Selection and cultivation of strains high producers of pigments with antioxidant properties (astaxanthin, lutein, zeaxanthin)
  2. Selection of species with high polyunsaturated fatty acid content (EPA, DHA)
  3. Selection of species able to produce bioactive substances (anti-inflammatory , antiviral, antimicrobial compounds)
  4. Microalgae as Health food
  5. Microalgae as aquaculture feed

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Facilities

  • Microalgal strains for the production of bio-hydrogen and bio-diesel
  • Laboratory equipment for microalgae cultivation
  • Equipment for laboratory scale hydrogen production by photosynthetic microorganisms
  • Equipment for outdoor hydrogen production by photosynthetic microorganisms
  • Closed photobioreactors for Bio-diesel production by microalgae
  • Closed Photobioreactors for cultivation of photosynthetic microorganisms
  • Open Ponds for outdoor microalgae cultivation​

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Some ongoing research projects

  • Research on the production of renewable Energy through microalgae. In particular, the researches are addressed toward the selection and optimization of hydrogen with D1 protein mutants of Chlamydomonas reinhardtii
  • Selection of species of microalgae suitable to be used in aquaculture
  • Selection of microalgal species with high lipid content for the production of biofuel
  • Studies on the acclimation process during exposure of cells to high light intensity outdoors
  • Optimization of biomass output in closed photobioreactors and open ponds
  • Recovery of nutrient from wastewater for microalgae cultivation.