title: Effects of temperature and pH on growth and antioxidant content of the microalga Scenedesmus obliquus.
abstract: Reactive forms of oxygen can damage DNA (among other molecules), thus triggering, e.g., atherogenesis and carcinogenesis. However, such dietary antioxidants as lutein and β-carotene can effectively inactivate them; these compounds were found to high levels in a novel strain (M2-1) of the microalga Scenedesmus obliquus. The independent and combined effects of pH and temperature on its rates of growth and production of antioxidants were experimentally assessed, via a full factorial experimental design; the effects of each parameter independently, and of their interactions were accordingly quantified by ANOVA. Our results indicated that temperature plays a more important role on the maximum specific growth rate than pH; in terms of antioxidant content, pH and, to a lesser extent, temperature also have relevant effects. Consequently, the highest rate of biomass specific growth (0.294 ± 0.013 day(-1)) and biomass productivity (0.837 ± 0.054 mg L(-1) day(-1)) were associated with relatively low pH (6) and relatively high temperature (30°C). Conversely, the antioxidant production rate increased with pH; hence, the highest productivity (0.638 mg L(-1) day(-1)) was attained at pH 8 and 30°C. At the best operating conditions for antioxidant content, the levels of lutein and β-carotene were 203.57 ± 1.41 and 18.20 ± 0.33 mg mL(-1), respectively; the maximum production of either one occurred at the early exponential phase.
authors.affiliation: CBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal.
authors.forename: A Catarina
authors.initials: AC
authors.lastname: Guedes
authors.forename: Helena M
authors.initials: HM
authors.lastname: Amaro
authors.forename: Ricardo D
authors.initials: RD
authors.lastname: Pereira
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Malcata
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D018533:Biomass; D006863:Hydrogen-Ion Concentration; D044444:Scenedesmus / Q000254:growth & development* / Q000378:metabolism*; D013696:Temperature
chemical_list: D000975:Antioxidants