title: Optimization of photobioreactor growth conditions for a cyanobacterium expressing mosquitocidal Bacillus thuringiensis Cry proteins.
abstract: An Anabaena strain (PCC 7120#11) that was genetically engineered to express Bacillus thuringiensis subsp. israelensis cry genes has shown good larvicidal activity against Anopheles arabiensis, a major vector of malaria in Africa. Response surface methodology was used to evaluate the relationship between key growth factors and the volumetric productivity of PCC 7120#11 in an indoor, flat-plate photobioreactor. The interaction of input CO₂ concentration and airflow rate had a statistically significant effect on the volumetric productivity of PCC 7120#11, as did the interaction of airflow rate and photosynthetic photon flux density. Model-based numerical optimization indicated that the optimal factor level combination for maximizing PCC 7120#11 volumetric productivity was a photosynthetic photon flux density of 154 μmol m⁻² s⁻¹ and air enriched with 3.18% (v/v) CO₂ supplied at a flow rate of 1.02 vessel volumes per minute. At the levels evaluated in the study, none of the growth factors had a significant effect on the median lethal concentration of PCC 7120#11 against An. arabiensis larvae. This finding is important because loss of mosquitocidal activity under growth conditions that maximize volumetric productivity would impact on the feasibility of using PCC 7120#11 in malaria vector control programs. The study showed the usefulness of response surface methodology for determination of the optimal growth conditions for a cyanobacterium that is genetically engineered to have larvicidal activity against malaria vectors.
authors.affiliation: School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Irene
authors.initials: I
authors.lastname: Ketseoglou
authors.forename: Gustav
authors.initials: G
authors.lastname: Bouwer
mesh_terms: D000818:Animals; D000852:Anopheles; D001413:Bacillus thuringiensis / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism*; D002245:Carbon Dioxide / Q000494:pharmacology; D000458:Cyanobacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004731:Endotoxins / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000378:metabolism*; D007814:Larva; D010572:Pest Control, Biological; D058433:Photobioreactors
chemical_list: D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D002245:Carbon Dioxide
keywords: ANOVA; Anabaena PCC 7120#11; Bacillus thuringiensis subsp. israelensis; Bacillus thuringiensis subspecies israelensis; Bti; LC(50); Mosquitocidal; PAR; PPFD; Photobioreactor; RSM; Response surface methodology; analysis of variance; median lethal concentration; photosynthetic photon flux density; photosynthetically active radiation; response surface methodology; revolutions per minute; rpm; vessel volumes per minute; vvm