Membrane-Located Expression of Thioesterase From Acinetobacter baylyi Enhances Free Fatty Acid Production With Decreased Toxicity in Synechocystis sp. PCC6803

Enhanced beneficial lipids and volatile compounds in Jersey ghee attributed by key microbiota

Ghee, a traditional fermented dairy product and dietary staple for inhabitants of the Tibet Plateau, has unclear lipid profiles and flavor formation mechanisms. This study aims to characterize superior ghee varieties and elucidate factors driving the production of beneficial lipids and flavor compounds. Through a comprehensive analysis of lipidomic profiles, volatile organic compound (VOC) release and microbial dynamics during ghee production from Holstein milk (HM) and Jersey milk (JM), A total of 126 differential lipids were identified, primarily associated with glycerophospholipid and sphingolipid metabolism. Additionally, 69 VOCs were detected, with 23 recognized as critical to flavor development. Key microbial species, including Lactococcus, Lactobacillus, Acetobacter, and Lacticaseibacillus, enriched during fermentation, were found to drive both VOC release and free fatty acid (FFA) production, particularly of eicosapentaenoic acid (EPA) and long-chain fatty acids. Notably, ghee derived from JM exhibited higher levels of functional lipids, beneficial FFAs, and critical VOCs compared to Holstein ghee (HG). The fermentation process, supported by microbial activity and enzyme production, significantly enriched these compounds, underscoring the pivotal role of microbes in enhancing both health benefits and flavor. These findings have potential implications for improving the quality of fermented dairy products in the food industry.

Insufficient Acetyl-CoA Pool Restricts the Phototrophic Production of Organic Acids in Model Cyanobacteria

Cyanobacteria are promising biological chassis to produce biochemicals such as carboxylic acids and their derivatives from CO2. In this manuscript, we reflected on cyanobacterial acetyl-CoA pool and TCA cycle as an important source of precursor molecules for the biosynthesis of carboxylic acids such as 3-hydroxypropionate, 3-hydroxybutyrate, succinate, malate, fumarate and free fatty acids, each of which is an important platform chemical for bioeconomy. We further highlighted specific features of the cyanobacterial TCA cycle, how it differs in structure and function from widely described TCA cycles of heterotrophic model organisms, and methods to make it more suitable for the production of carboxylic acids from CO2. Currently, the yields of these compounds are significantly lower than those in heterotrophic organisms and it was concluded that the primary cause of this can be attributed to the limited flux toward acetyl-CoA. Strategies like overexpressing pyruvate dehydrogenase complex or introducing synthetic bypasses are being explored to overcome these limitations. While significant progress has been made, further research is needed to enhance the metabolic efficiency of cyanobacteria, making them viable for the large-scale, sustainable production of carboxylic acids and their derivatives.

Microalgae biofuels: illuminating the path to a sustainable future amidst challenges and opportunities

The development of microalgal biofuels is of significant importance in advancing the energy transition, alleviating food pressure, preserving the natural environment, and addressing climate change. Numerous countries and regions across the globe have conducted extensive research and strategic planning on microalgal bioenergy, investing significant funds and manpower into this field. However, the microalgae biofuel industry has faced a downturn due to the constraints of high costs. In the past decade, with the development of new strains, technologies, and equipment, the feasibility of large-scale production of microalgae biofuel should be re-evaluated. Here, we have gathered research results from the past decade regarding microalgae biofuel production, providing insights into the opportunities and challenges faced by this industry from the perspectives of microalgae selection, modification, and cultivation. In this review, we suggest that highly adaptable microalgae are the preferred choice for large-scale biofuel production, especially strains that can utilize high concentrations of inorganic carbon sources and possess stress resistance. The use of omics technologies and genetic editing has greatly enhanced lipid accumulation in microalgae. However, the associated risks have constrained the feasibility of large-scale outdoor cultivation. Therefore, the relatively controllable cultivation method of photobioreactors (PBRs) has made it the mainstream approach for microalgae biofuel production. Moreover, adjusting the performance and parameters of PBRs can also enhance lipid accumulation in microalgae. In the future, given the relentless escalation in demand for sustainable energy sources, microalgae biofuels should be deemed a pivotal constituent of national energy planning, particularly in the case of China. The advancement of synthetic biology helps reduce the risks associated with genetically modified (GM) microalgae and enhances the economic viability of their biofuel production.

Overexpression of lipA or glpD_RuBisCO in the Synechocystis sp. PCC 6803 Mutant Lacking the Aas Gene Enhances Free Fatty-Acid Secretion and Intracellular Lipid Accumulation

Although engineered cyanobacteria for the production of lipids and fatty acids (FAs) are intelligently used as sustainable biofuel resources, intracellularly overproduced FAs disturb cellular homeostasis and eventually generate lethal toxicity. In order to improve their production by enhancing FFAs secretion into a medium, we constructed three engineered Synechocystis 6803 strains including KA (a mutant lacking the aas gene), KAOL (KA overexpressing lipA, encoding lipase A in membrane lipid hydrolysis), and KAOGR (KA overexpressing quadruple glpD/rbcLXS, related to the CBB cycle). Certain contents of intracellular lipids and secreted FFAs of all engineered strains were higher than those of the wild type. Remarkably, the KAOL strain attained the highest level of secreted FFAs by about 21.9%w/DCW at day 5 of normal BG₁₁ cultivation, with a higher growth rate and shorter doubling time. TEM images provided crucial evidence on the morphological changes of the KAOL strain, which accumulated abundant droplets on regions of thylakoid membranes throughout the cell when compared with wild type. On the other hand, BG₁₁-N condition significantly induced contents of both intracellular lipids and secreted FFAs of the KAOL strain up to 37.2 and 24.5%w/DCW, respectively, within 5 days. Then, for the first time, we shone a spotlight onto the overexpression of lipA in the aas mutant of Synechocystis as another potential strategy to achieve higher FFAs secretion with sustainable growth.

Photosynthetic Conversion of Carbon Dioxide to Oleochemicals by Cyanobacteria: Recent Advances and Future Perspectives

Sustainable production of biofuels and biochemicals has been broadly accepted as a solution to lower carbon dioxide emissions. Besides being used as lubricants or detergents, oleochemicals are also attractive biofuels as they are compatible with existing transport infrastructures. Cyanobacteria are autotrophic prokaryotes possessing photosynthetic abilities with mature genetic manipulation systems. Through the introduction of exogenous or the modification of intrinsic metabolic pathways, cyanobacteria have been engineered to produce various bio-chemicals and biofuels over the past decade. In this review, we specifically summarize recent progress on photosynthetic production of fatty acids, fatty alcohols, fatty alk(a/e)nes, and fatty acid esters by genetically engineered cyanobacteria. We also summarize recent reports on fatty acid and lipid metabolisms of cyanobacteria and provide perspectives for economic cyanobacterial oleochemical production in the future.