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.

中文翻译：

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双歧双歧杆菌作为生物柴油剂：通过微波辅助直接原位酯交换反应鉴定脂肪酸甲酯。

人们越来越关注与化石燃料使用相关的环境和经济问题，这引起了人们对蓝细菌作为第三代生物燃料制剂的极大兴趣。在这项研究中，模型光合作用蓝细菌弗雷米氏菌双歧杆菌的生物柴油潜力通过直接酯交换反应由脂肪酸甲酯（FAME）鉴定。通过重量分析确定的野生型（Fd33）和卤代抗性（HSF33-1和HSF33-2）菌株中的总脂质产生的HSF33-1细胞干重（CDW）为19％，HSF33-2为20％CDW，与Fd33（18％CDW）。气相色谱-质谱法在酯交换的脂质中检测到较高的饱和FAME与不饱和FAME比例（2.48–2.61），其中棕榈酸甲酯含量最高（C16：0）。虽然理论上的生物柴油特性显示出十六烷值高和氧化稳定性高，但浊点和倾点值高表明燃料混合可能是一种可行的方法。HSF33-1（40.2％）和HSF33-2（69.9％）的总酯交换脂质中的FAME丰度相对于Fd33（25。使用全面的二维气相色谱仪与飞行时间质谱联用，确定了4％），这表明强大的盐胁迫响应对应于较高水平的可萃取FAME。烷烃是常规燃料的关键成分，F. diplosiphon在所有菌株中酯交换的脂质都证实了在生物柴油生产过程中不会抑制这些烃的天然合成。尽管对光合色素和藻胆蛋白的分析没有发现显着差异，但野生型和卤代耐盐菌株中的FAME丰度差异很大，这表明光合途径并不是决定脂肪酸产生的唯一因素。我们表征了F. diplosiphon用于生物燃料生产的潜力，在卤代耐盐菌株中的FAME产量高于野生型，光合作用色素沉着没有损失。