Cellular Cycling, Carbon Utilization, and Photosynthetic Oxygen Production during Bicarbonate-Induced Triacylglycerol Accumulation in a Scenedesmus sp.

Abstract

Microalgae are capable of synthesizing high levels of triacylglycerol (TAG) which can be used as precursor compounds for fuels and specialty chemicals. Algal TAG accumulation typically occurs when cellular cycling is delayed or arrested due to nutrient limitation, an environmental challenge (e.g., pH, light, temperature stress), or by chemical addition. This work is a continuation of previous studies detailing sodium bicarbonate-induced TAG accumulation in the alkaline chlorophyte Scenedesmus sp. WC-1. It was found that upon sodium bicarbonate amendment, bicarbonate is the ion responsible for TAG accumulation; a culture amendment of approximately 15 mM bicarbonate was sufficient to arrest the cellular cycle and switch the algal metabolism from high growth to a TAG accumulating state. However, the cultures were limited in dissolved inorganic carbon one day after the amendment, suggesting additional carbon supplementation was necessary. Therefore, additional abiotic and biotic experimentation was performed to evaluate in-and out-gassing of CO 2 . Cultures to which 40-50 mM of sodium bicarbonate were added consumed DIC faster than CO 2 could ingas during the light hours and total photosynthetic OPEN ACCESSEnergies 2013, 6 6061 oxygen production was elevated as compared to cultures that did not receive supplemental inorganic carbon.

Overview of Carbon Capture Technology: Microalgal Biorefinery Concept and State-of-the-Art

“…The fatty acid composition of most of the microalgae is dominated by C14:0, C16:0, C18:1, C18:2, and C18:3 fatty acids, yet the relative composition varies from species to species (Gouveia and Oliveira, 2009). Also, the role of HCO 3 − in inducing TAG accumulation has been widely illustrated recently (Gardner et al, 2012(Gardner et al, , 2013Lam et al, 2012;White et al, 2013). The lipids can be converted into FAMEs (fatty acid methyl esters) via transesterification for biodiesel production.…”

Physiological responses of freshwater oleaginous microalgae Desmodesmus sp. NMX451 under nitrogen deficiency and alkaline pH-induced lipid accumulation

“…Furthermore, the delayed cell cycle observed in bicarbonate supplemented cultures may also prevent the oil from being assimilated for energy for cell division (Matusiak-Mikulin et al 2006). Thus, bicarbonate was directly or indirectly responsible for induced TAG accumulation (Gardner et al 2013b). …”

Physiological and biochemical responses of the green algaPachycladella chodatii(SAG 2087) to sodicity stress

“…Twenty milliliters of exponential cultures were centrifuged, standardized at an optical density at 680 nm of 0.1, and inoculated into 300 ml of BG11 medium in 500 ml Erlenmeyer flasks in triplicate. The effect of different carbon source namely Na 2 CO 3 [(control (20 mg l À1 ), 100% (40 mg l À1 ), 150% (60 mg l À1 ) and 200% (80 mg l À1 )], NaHCO 3 [(control (0 mg l À1 ), (15,45, 75 mg l À1 )], on growth and biochemical composition of P. chodatii were studied. The cultures were grown as previously mentioned conditions.…”

“…The results indicated that, the low concentration (40 and 15 mg l À1 ) of Na 2 CO 3 and NaHCO 3 , respectively, led to increasing the total lipids, but reversible trend was observed when the culture of P. chodatii treated with higher concentrations of Na 2 CO 3 and NaHCO 3 . Gardner et al [45] reported that, inorganic carbon sources mostly could be one of the chief factors that help improve the carotenoids and lipids content in the algal cells by improving photosynthetic efficiency and growth rate. Zheng et al [46] demonstrated that, lipid yield of C. vulgaris reached its peak with the concentration increase of the inorganic carbon source after 10 days cultivation, but dropped again by further increase of the concentration.…”

“…Zheng et al [46] demonstrated that, lipid yield of C. vulgaris reached its peak with the concentration increase of the inorganic carbon source after 10 days cultivation, but dropped again by further increase of the concentration. Inorganic carbon, in the form of bicarbonate (HCO 3 -À ), is an effective lipid accumulation trigger [45]. Furthermore, it was recently shown that the addition of sodium bicarbonate is a viable strategy to increase lipid accumulation in marine Chlorophytes [47] and Dunaliella sp.…”