Insights into cyanobacterial alkane biosynthesis

Abstract

Alkanes are high-energy molecules that are compatible with enduring liquid fuel infrastructures, which make them highly suitable for being next-generation biofuels. Though biological production of alkanes has been reported in various microorganisms, the reports citing photosynthetic cyanobacteria as natural producers have been the most consistent for the long-chain alkanes and alkenes (C15–C19). However, the production of alkane in cyanobacteria is low, leading to its extraction being uneconomical for commercial purposes. In order to make alkane production economically feasible from cyanobacteria, the titre and yield need to be increased by several orders of magnitude. In the recent past, efforts have been made to enhance alkane production, although with a little gain in yield, leaving space for much improvement. Genetic manipulation in cyanobacteria is considered challenging, but recent advancements in genetic engineering tools may assist in manipulating the genome in order to enhance alkane production. Further, advancement in a basic understanding of metabolic pathways and gene functioning will guide future research for harvesting the potential of these tiny photosynthetically efficient factories. In this review, our focus would be to highlight the current knowledge available on cyanobacterial alkane production, and the potential aspects of developing cyanobacterium as an economical source of biofuel. Further insights into different metabolic pathways and hosts explored so far, and possible challenges in scaling up the production of alkanes will also be discussed.

Incorporation, fate, and turnover of free fatty acids in cyanobacteria

“…Coates and collaborators (Coates et al 2014 ) characterized the distribution of hydrocarbon biosynthetic pathways across cyanobacteria. They concluded that most cyanobacteria, including Synechocystis 6803, harbor the two-step acyl-ACP reductase/aldehyde-deformylating oxygenase (Aar/Ado) pathway, producing C15 or C17 alkanes (Schirmer et al 2010 , Parveen and Yazdani 2022 ). Still, Aar enzymes were found to vary in activity, substrate specificity, and solubility with host habitat.…”

The volatilome reveals microcystin concentration, microbial composition, and oxidative stress in a critical Oregon freshwater lake

“…The associations between SFAs and microcystin concentration in our elastic net models indicate that the relative abundances of SFAs shift during oxidative stress. SFAs accumulate between the lipid bilayers of cyanobacterial thylakoid and cytoplasmic membranes 50,88 where they contribute to membrane structure and help ne-tune localization of photosynthetic machinery 50 during temperature and light stress 49,50,89 . Cyanobacteria use an acyl-ACP reductase/aldehyde-deformylating oxygenase (ADO) pathway to produce fatty aldehydes of decreasing chain length (C n , C n-1 , C n-2 …; Fig 7).…”

Recent advances in the improvement of cyanobacterial enzymes for bioalkane production

“…Subsequently, ADO converts the aldehydes into 15- or 17-carbon alkanes (pentadecane or heptadecane, respectively) and formate (Fig. 1 ) [ 13 , 22 , 24 – 26 ]; ADO produces alkenes if the aldehyde substrates are monounsaturated. Notably, alkanes have been produced via heterologous expression of AAR and ADO in Escherichia coli , indicating that these enzymes are essential for alkane biosynthesis [ 13 , 22 ].…”