Enhanced photosynthesis and characterisation of carbohydrate production of Synechococcus PCC 7002
Authors
Romero, David Sanchez ; Steffen, Christine Sophie
Term
4. term
Education
Publication year
2019
Submitted on
2019-06-10
Pages
54
Abstract
Cyanobakterier er fotosyntetiserende mikroorganismer, der kan danne kulhydrater ud fra CO2 uden at bruge dyrkbar jord. Det gør dem interessante som råvareleverandører til bioraffinaderier. For at øge kulhydratproduktionen undersøgte vi, om en mere effektiv fotosyntese kunne hjælpe. I Synechococcus sp. PCC 7002 overudtrykte vi et bifunktionelt enzym, BiBPase (fruktose-1,6-bisfosfatase/sedoheptulose-1,7-bisfosfatase), i en modificeret stamme kaldet trcBiBP. Vi sammenlignede vækst og kulhydratsammensætning mellem vildtype og trcBiBP. Væksten blev fulgt ved at måle lysabsorption ved 730 nm (OD730), og cellerne blev undersøgt med mikroskopi og Nile Red-farvning (en fluorescerende farve). Glukose, sukrose, glykogen og cellulose blev kvantificeret ved enzymatisk nedbrydning efterfulgt af glukosemåling med en farvereaktion (GOPOD). TrcBiBP-celler var større og voksede langsommere end vildtypen og havde højere indhold af glykogen og cellulose. Stigningerne i kulhydrater var dog ikke statistisk signifikante, sandsynligvis på grund af variation i vækstbetingelserne i forsøget. Resultaterne var delvist uoverensstemmende med en tidligere undersøgelse (De Porcellinis et al., 2014), der rapporterede hurtigere vækst og lavere glykogen i trcBiBP. Denne forskel kan skyldes forskellige metoder til selektion og vedligeholdelse af trcBiBP-celler. Vi overvejede, om langsommere vækst skyldtes mangel på kvælstof i mediet, men kvælstofmangel påvirkede kun i ringe grad vækst og glykogen i trcBiBP. Derimod øgede kvælstofmangel markant glykogenindholdet i vildtypen, i tråd med litteraturen (Möllers et al., 2014). Samlet set peger resultaterne på, at vildtype Synechococcus PCC 7002 under kvælstofmangel er en mere lovende producent af kulhydrater til bioraffinaderier end den genetisk modificerede trcBiBP-stamme.
Cyanobacteria are photosynthetic microorganisms that can make carbohydrates from CO2 without using arable land, which makes them attractive feedstocks for biorefineries. To boost carbohydrate production, we tested whether enhancing photosynthesis would help. In Synechococcus sp. PCC 7002, we overexpressed a bifunctional enzyme, BiBPase (fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase), creating a modified strain called trcBiBP. We compared growth and carbohydrate composition between the wild type and trcBiBP. Growth was tracked by measuring light absorption at 730 nm (OD730), and cells were examined with microscopy and Nile Red staining (a fluorescent dye). Glucose, sucrose, glycogen, and cellulose were quantified by enzymatic digestion followed by glucose measurement using a colorimetric GOPOD assay. TrcBiBP cells were larger, grew more slowly, and had higher glycogen and cellulose levels than the wild type. However, these increases in carbohydrates were not statistically significant, likely due to variability in growth conditions. The results partly disagreed with a previous study (De Porcellinis et al., 2014) that reported faster growth and lower glycogen in trcBiBP; this discrepancy may reflect different methods for selecting and maintaining trcBiBP cells. We hypothesized that slower growth might be caused by insufficient nitrogen in the medium, but nitrogen deprivation had little effect on trcBiBP growth and glycogen. In contrast, nitrogen deprivation significantly increased glycogen in the wild type, consistent with literature (Möllers et al., 2014). Overall, under our conditions, wild-type Synechococcus PCC 7002 under nitrogen deprivation appears to be a more promising carbohydrate producer for biorefineries than the engineered trcBiBP strain.
[This abstract was generated with the help of AI]
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