Improving the biomass productivity and phycocyanin concentration by mixotrophic cultivation of Arthrospira platensis
Author
Rybner, Tobias Valdemar
Term
4. term
Education
Publication year
2016
Submitted on
2016-06-10
Pages
57
Abstract
Arthrospira platensis er en fotosyntetisk (fototrof) mikroorganisme, der naturligt danner det blå pigment phycocyanin. Den dyrkes ofte i åbne raceway-damme, som er udsatte for kontaminering og har lav produktivitet. Mange af disse udfordringer kan mindskes ved dyrkning i lukkede fotobioreaktorer, men lukkede systemer er stadig dyre, primært på grund af højt energiforbrug. En måde at sænke energiforbruget er at forkorte dyrkningstiden ved at øge væksten og at bruge energieffektive LED-lyskilder. I dette studie blev der undersøgt, om tilsætning af acetat som organisk kulstofkilde (mixotrof dyrkning: brug af lys plus tilført kulstof) kan øge produktiviteten af A. platensis under forskellige lysbetingelser, og hvordan dette påvirker indholdet af phycocyanin. Sammenlignet med fuldt autotrof dyrkning (kun lys og uorganisk kulstof) voksede de mixotrofe kulturer hurtigere: den gennemsnitlige biomasseproduktivitet steg med ca. 20 %. Indholdet af phycocyanin per gram biomasse var dog det samme i autotrofe og mixotrofe kulturer. Lavere lysintensiteter så ud til at øge phycocyanin-indholdet, mens dyrkning med kun rødt lys ikke så ud til at ændre phycocyanin-indholdet. Der blev også observeret en negativ sammenhæng mellem biomassetæthed og phycocyanin-indhold: tættere kulturer indeholdt mindre phycocyanin per gram. Samlet set tyder resultaterne på, at tilsætning af acetat kan øge biomasseproduktiviteten, og at lav lysintensitet kan øge phycocyanin-indholdet. Tilsammen indikerer dette, at anvendelse af acetat ved lavt lys kan forbedre produktionen af phycocyanin og samtidig reducere energiforbruget i lukkede dyrkningssystemer.
Arthrospira platensis is a photosynthetic (phototrophic) microorganism that naturally produces the blue pigment phycocyanin. It is often grown in open raceway ponds, which are vulnerable to contamination and typically have low productivity. Many of these issues can be reduced by growing the organism in closed photobioreactors, but closed systems remain expensive mainly because they use a lot of energy. One way to cut energy use is to shorten cultivation time by boosting growth and to use efficient LED lighting. This study tested whether adding acetate as an organic carbon source (mixotrophic cultivation: using light plus an added carbon source) could increase the productivity of A. platensis under different light conditions, and how these choices affect phycocyanin content. Compared with fully autotrophic cultures (relying only on light and inorganic carbon), mixotrophic cultures grew faster: average biomass productivity increased by about 20%. However, the amount of phycocyanin per gram of biomass was similar in autotrophic and mixotrophic cultures. Lower light intensities tended to increase phycocyanin content, while using only red light did not noticeably change phycocyanin content. A negative relationship was also observed between biomass density and phycocyanin content: denser cultures contained less phycocyanin per gram. Overall, the results suggest that supplying acetate can raise biomass productivity, and that operating at low light intensities can raise phycocyanin content. Together, these findings indicate that using acetate at low light could improve phycocyanin production while reducing energy consumption in closed cultivation systems.
[This abstract was generated with the help of AI]
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