Fremyella diplosiphon as a Biodiesel Agent: Identification of Fatty Acid Methyl Esters via Microwave-Assisted Direct In Situ Transesterification

Abstract

Increasing concerns on environmental and economic issues linked to fossil fuel use has driven great interest in cyanobacteria as third generation biofuel agents. In this study, the biodiesel potential of a model photosynthetic cyanobacterium, Fremyella diplosiphon, was identified by fatty acid methyl esters (FAME) via direct transesterification. Total lipids in wild type (Fd33) and halotolerant (HSF33-1 and HSF33-2) strains determined by gravimetric analysis yielded 19% cellular dry weight (CDW) for HSF33-1 and 20% CDW for HSF33-2, which were comparable to Fd33 (18% CDW). Gas chromatography-mass spectrometry detected a high ratio of saturated to unsaturated FAMEs (2.48-2.61) in transesterified lipids, with methyl palmitate being the most abundant (C16:0). While theoretical biodiesel properties revealed high cetane number and oxidative stability, high cloud and pour point values indicated that fuel blending could be a viable approach. Significantly high FAME abundance in total transesterified lipids of HSF33-1 (40.2%) and HSF33-2 (69.9%) relative to Fd33 (25.4%) was identified using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry, indicating that robust salt stress response corresponds to higher levels of extractable FAME. Alkanes, a key component in conventional fuels, were present in F. diplosiphon transesterified lipids across all strains confirming that natural synthesis of these hydrocarbons is not inhibited during biodiesel production. While analysis of photosynthetic pigments and phycobiliproteins did not reveal significant differences, FAME abundance varied significantly in wild type and halotolerant strains indicating that photosynthetic pathways are not the sole factors that determine fatty acid production. We characterize the potential of F. diplosiphon for biofuel production with FAME yields in halotolerant strains higher than the wild type with no loss in photosynthetic pigmentation.

Nutrient removal and microalgal biomass production from different anaerobic digestion effluents with Chlorella species

“…Microalgal biomass has been considered a potential feedstock for producing biodiesel, as microalgae accumulate large amounts of assimilated carbon in the form of lipids in the cell. Microalgae have several advantages as a biodiesel feedstock over conventionally used terrestrial plants, including higher lipid content, faster growth, higher biomass yield, and little competition for arable land 11–13 . However, substantial amounts of water and nutrients (often added as chemical salts) are required for the cultivation of microalgae, raising concern over its economic feasibility 14 .…”

Nitrogen Deprivation in Fremyella diplosiphon Augments Lipid Production without Affecting Growth

“…To investigate the effect of nitrate deprivation on the F. diplosiphon fatty acid profile, cultures were grown under conditions mentioned above and extracted lipids were subjected to one-step direct transesterification in a multimode commercial scientific reaction microwave (CEM Corp, Matthews, NC, USA) as described by Tabatabai et al [36].…”

“…The fatty acid composition of F. diplosiphon transesterified product was determined using Shimadzu GC17A/QP5050A gas chromatography-mass spectrometry (GC-MS) according to the method described by Rosenberg et al [39] and Tabatabai et al [36]. Peaks were identified by comparing mass spectra to the lipid Web Archive of FAME mass spectra.…”

“…By contrast, a previous study in Botrycoccus sp., Scenedesmus obliquus, and Chlorella pyrenoidosa revealed that the organism exhibited a significant reduction in growth when subjected to nitrogen starvation [7,28,48,49]. The fatty acid composition of F. diplosiphon transesterified product was determined using Shimadzu GC17A/QP5050A gas chromatography-mass spectrometry (GC-MS) according to the method described by Rosenberg et al [39] and Tabatabai et al [36]. Peaks were identified by comparing mass spectra to the lipid Web Archive of FAME mass spectra.…”

“…Biofuels are renewable green fuels, which have driven interest in methods to maximize production and attracted researchers to meet the growing demand for fuel [2]. Their production offers an opportunity to develop an alternative for fossil fuels that prove its efficacy as a biodiesel agent [36]. In this study, we investigated the growth response and lipid yield of F. diplosiphon when subjected to varying levels of sodium nitrate (NaNO 3 ) in the culture medium.…”