Trophic conversion of microalgae

Objective

• Two-stage cultivation – transfers from heterotrophic to phototrophic growth mode. The aim is to increase quality/value of biomass (content of bioactive compounds).
• To study physiological changes in microalgae cultures that accompany trophic conversion from heterotrophic to phototrophic growth regime in various cultivation units (photobioreactors).
• Laboratory as well as outdoor trials in various cultivation using selected production strains (Chlorella, Haematococcus and others).
• Use of an array of methods should give us a better understanding of the interplay among physiological activities, growth and productivity during trophic conversion process.
• To find which key growth conditions and variables are crucial for trophic conversion in order to control/manipulate this process.

Main topic

Microalgae are grown in mass cultures to produce biomass that contain a number of high-value products. Phototrophic growth is often slow due to light and other limitations. Some microalgae can also grow heterotrophically (using organic carbon sources) that is a fast process, but the content of some bioactive compounds (e.g. pigments) in biomass is low.Some species are able to undergo trophic conversions from heterotrophic to phototrophic growth mode as to produce high density cell cultures in the 1st stage and then, in the 2nd stage is transferred to a phototrophic regime (photoinduction) to enhance target products such as intracellular proteins, pigments and lipids. Physiological changes behind trophic conversions have to be elucidated in order to manipulate this biotechnological process. Using a trophic conversion strategy high biomass productivity and quality can be achieved, indicating that this strategy provides a promising way to boost economic benefit and considerably reduce production costs.

This two-stage process is a promising strategy as to provide a more efficient way for large scale production of microalgae biomass containing valuable compounds.

Coordinators:               

Leading co-ordinator: Félix Lopez Figueroa (University of Málaga, Spain)
Local co-ordinator: Jiří Masojídek (Centre Algatech, Třeboň, Czech Republic)
Local team leader: Karolína Ranglová (Centre Algatech, Třeboň, Czech Republic)

Participants:   

Number of participants: 10-15

Location: 

Field experiments: None
Lab experiments: Centre Algatech, Institute of Microbiology in Třeboň
Data management: Centre Algatech, Institute of Microbiology in Třeboň

Experimental plan: 

Microalgae cultures will be grown firstly in flasks or fermenters in heterotrophic mode (dark, organic substrate). Then, the cells are harvested, washed and transferred to inorganic medium. We intend to combine physiological methods (variable fluorescence - ETR, oxygen evolution) with biochemical analysis of cell composition (pigments, lipids, proteins and carbohydrates) and quantitative genomics and proteomics to understand the processes of trophic conversion.

In a series of laboratory and diurnal field trials, heterotrophically-grown microalgae cultures will be exposed to light and cultured phototrophically. Key physiological variables and biomass quality (e.g. pigments, lipid, proteins and carbohydratecontent) will be monitored to study the influence of growth conditions on the process of trophic conversions. We will set-up several experimental ‘nests’ focusing on various techniques (physiological and biochemical analyses, oxygen measurement, fluorescence, advanced biomass analyses, etc.). Diel sampling will be done every 2-4 hours during trials. Various outdoor and laboratory cultivation units (photobioreactors) will be compared.

Equipment available: 

• Standard systems for laboratory cultivation, outdoor cultivation units (24 and 90 m² thin-layer cascade), photobioreactors (100-L flat panel PBR placed in a greenhouse – artificial + natural light; 10-L, 100-L and 1,000-L PBRswith LED illumination
• Standard equipment for biochemical extractions and purifications
• Cell counter
• Various bench-top and portable fluorometers for measurements of fluorescence quenching and induction kinetics (AquaPen AP-100, PAM 101-103, PAM-2500, Junior-PAM, Diving-PAM, Multicolor-PAM).
• Bio-optic analysis by using spectrophotometry and spectroradiometry (Multidiodespectroradiometers as Sphere Optic and Ocean optics) and in-situ irradiance measurements by using PAR sensors
• Oxylabs to measure photosynthetic oxygen production and respiration
• Spectrofluorometers for measuring emission and excitation spectra (also for 77K)
• HPLC for pigment analysis
• FTIR spectrometer for semiquantitative analysis of biomass composition
• High precision GC and LC MS for proteomic and metabolomicanalyses (including fatty acids and small organic molecules).

Alternatively we can employ other techniques according to participant suggestions, skills and their equipment delivered.

Equipment in demand:

• Optode oxygen measurement system(one available from Malaga University) or Clark oxygen measurement system (one available from Malaga University)
• More Junior-PAMs to measure Chl fluorescence in-situ (some available from Malaga University?)