Light and oxygen stress in Spirulina platensis (cyanobacteria) grown outdoors in tubular reactors

Abstract

As the effects of light and oxygen stress in algae on mass culture has not been intensively studied, we investigated them in Spirulina platensis under outdoor conditions in controlled tubular reactors where the respective roles of each stress can be distinguished. It was observed that exposure of this cyanobacterium at two oxygen concentrations (ca 20 and 53 mg 1−1) caused very little change in the ratio between variable and maximum fluorescence (Fv/Fm) during the day even when the culture was grown at higher oxygen concentration (about 7% lower in the evening than in the morning). Vice‐versa, when the photochemical efficiency of PSII (photon yield, Φc) was measured, a reduction of about 20% was observed. Neither the Fv/Fm ratio nor the Φc of the culture grown at the lower oxygen concentration changed significantly during the day. The daily productivity of the culture exposed to the higher oxygen concentration was reduced by about 20%. Laboratory cultures bubbled with air or pure oxygen under continuous light showed a similar response; i.e., a smaller decrease in Fv/Fm (17%) than in the Φc (56%) after 4 h. After 32 h of culture in pure oxygen, a total lysis of the cells occurred. Our results support the hypothesis that photoinhibition and photooxidation, two traditionally linked terms, although often closely associated under similar environmental conditions, may comprise two types of stress with different sites of inhibition.

Effect of oxygen concentration on the growth of Nannochloropsis sp. at low light intensity

“…The decrease in quantum yield of S. platensis (Vonshak et al 1996) and C. sorokiniana (Ugwu et al 2007) proved to be accompanied by a gradual decrease in the ratio between variable and maximum fluorescence. This indicates that higher oxygen concentrations cause destruction of the chlorophyll via photo-oxidative inhibition.…”

Evolution, detrimental effects, and removal of oxygen in microalga cultures: A review

“…As shown in Table , a DO of 55‐60 mg L –1 was reported for S. platenesis culture in a bench TPBR of 50 L made of 10 parallel Pyrex tubes with a length of 2 m and a diameter of 0.0485 m. Cultivation was carried out outdoor in water baths controlled at 35 o C. A biomass concentration of 1.4 g L –1 at a productivity of 0.417 g L –1 d –1 was achieved. The high DO levels observed within these short tubes of 2 m highlight the need of designing efficient deoxygenation mechanisms for TPBR since oxygen accumulation would increase with the increase of tube length if other conditions are the same.…”

“…Furthermore, it was observed that many algal species cannot withstand the exposure of 2‐3 hours to oxygen levels much above air saturation . Observation on the effect of extended exposure to oxygen on the growth of Spirulina indicated that irreversible damage took place after 30–32 h of exposure to the concentration of 36 mg L –1 oxygen . Moreover, a high degree of cell lysis and death of Chlorella sorokiniana was observed when DO exceeded 200% of air saturation (13 mg O 2 L –1 at 38°C) .…”

Development of a novel electrochemical system for oxygen control (ESOC) to examine dissolved oxygen inhibition on algal activity

“…To compensate for these effects, algae and higher plants can decrease the photosynthetic rate to reduce damage to the photosynthetic proteins (Osmond, ). These phenomena have been observed both in open (Moheimani and Borowitzka, ) and closed algal production systems (Molina et al, ; Pulz, ; Vonshak et al, ), where the inhibitory effects were commonly noted at dissolved oxygen levels approaching 36 mg L −1 .…”