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Microbial production of fatty acid-derived fuels and chemicals

Current Opinion in Biotechnology, 2013

Fatty acid metabolism is an attractive route to produce liquid transportation fuels and commodity oleochemicals from renewable feedstocks. Recently, genes and enzymes, which comprise metabolic pathways for producing fatty acid-derived compounds (e.g. esters, alkanes, olefins, ketones, alcohols, polyesters) have been elucidated and used in engineered microbial hosts. The resulting strains often generate products at low percentages of maximum theoretical yields, leaving significant room for metabolic engineering. Economically viable processes will require strains to approach theoretical yields, particularly for replacement of petroleum-derived fuels. This review will describe recent progress toward this goal, highlighting the scientific discoveries of each pathway, ongoing biochemical studies to understand each enzyme, and metabolic engineering strategies that are being used to improve strain performance.

Escherichia coli as a fatty acid and biodiesel factory: current challenges and future directions

Environmental science and pollution research international, 2016

Biodiesel has received widespread attention as a sustainable, environment-friendly, and alternative source of energy. It can be derived from plant, animal, and microbial organisms in the form of vegetable oil, fats, and lipids, respectively. However, biodiesel production from such sources is not economically feasible due to extensive downstream processes, such as trans-esterification and purification. To obtain cost-effective biodiesel, these bottlenecks need to be overcome. Escherichia coli, a model microorganism, has the potential to produce biodiesel directly from ligno-cellulosic sugars, bypassing trans-esterification. In this process, E. coli is engineered to produce biodiesel using metabolic engineering technology. The entire process of biodiesel production is carried out in a single microbial cell, bypassing the expensive downstream processing steps. This review focuses mainly on production of fatty acid and biodiesel in E. coli using metabolic engineering approaches. In the ...

Bacterial production of fatty acid and biodiesel: opportunity and challenges

Elsevier, 2020

Increasing population load and an altered lifestyle attitude are exerting extra pressure on the production market, to satisfy the demands and desire of society. The recently developed production and consumption models largely rely on fossil-based resources, which are affecting the environment and natural resources adversely. The cost-effective production of biological materials is an emerging sector with remarkable future prospects and provides many business opportunities. With time the research endeavors are gradually shifting toward bacterial lipids-derived biofuel production, which is more suitable and compatible for an industrial application. The major challenge in the overall process of the production of lipids-derived fuels from microbes is the involved carbon source as it contributes to more than half of the production cost. Therefore the production of lipids and biodiesel from bacteria using different waste materials as carbon source involving the application of advanced biotechnological tools, and modified transesterification reactions will make the biodiesel production cost effective.

Development of an orthogonal fatty acid biosynthesis system in E. coli for oleochemical production

Here we report recombinant expression and activity of several type I fatty acid synthases that can function in parallel with the native Escherichia coli fatty acid synthase. Corynebacterium glutamicum FAS1A was the most active in E. coli and this fatty acid synthase was leveraged to produce oleochemicals including fatty alcohols and methyl ketones. Coexpression of FAS1A with the ACP/CoA-reductase Maqu2220 from Marinobacter aquaeolei shifted the chain length distribution of fatty alcohols produced. Coexpression of FAS1A with FadM, FadB, and an acyl-CoA-oxidase from Micrococcus luteus resulted in the production of methyl ketones, although at a lower level than cells using the native FAS. This work, to our knowledge, is the first example of in vivo function of a heterologous fatty acid synthase in E. coli. Using FAS1 enzymes for oleochemical production have several potential advantages, and further optimization of this system could lead to strains with more efficient conversion to desired products. Finally, functional expression of these large enzyme complexes in E. coli will enable their study without culturing the native organisms.

From Fields to Fuels: Recent Advances in the Microbial Production of Biofuels

Amid grave concerns over global climate change and with increasingly strained access to fossil fuels, the synthetic biology community has stepped up to the challenge of developing microbial platforms for the production of advanced biofuels. The adoption of gasoline, diesel, and jet fuel alternatives derived from microbial sources has the potential to significantly limit net greenhouse gas emissions. In this effort, great strides have been made in recent years toward the engineering of microorganisms to produce transportation fuels derived from alcohol, fatty acid, and isoprenoid biosynthesis. We provide an overview of the biosynthetic pathways devised in the strain development of biofuel-producing microorganisms. We also highlight many of the commonly used and newly devised engineering strategies that have been employed to identify and overcome pathway bottlenecks and problems of toxicity to maximize production titers.

Enhanced Production of Fatty Acid Ethyl Ester with Engineered fabHDG Operon in Escherichia coli

Microorganisms

Biodiesel, or fatty acid ethyl ester (FAEE), is an environmentally safe, next-generation biofuel. Conventionally, FAEE is produced by the conversion of oil/fats, obtained from plants, animals, and microorganisms, by transesterification. Recently, metabolic engineering of bacteria for ready-to-use biodiesel was developed. In Escherichia coli, it is produced by fatty acyl-carrier proteins and ethanol, with the help of thioesterase (TesB) and wax synthase (WS) enzymes. One of the foremost barriers in microbial FAEE production is the feedback inhibition of the fatty acid (FA) operon (fabHDG). Here, we studied the effect of biodiesel biosynthesis in E. coli with an engineered fabHDG operon. With a basic FAEE producing BD1 strain harboring tes and ws genes, biodiesel of 32 mg/L were produced. Optimal FAEE biosynthesis was achieved in the BD2 strain that carries an overexpressed operon (fabH, fabD, and fabG genes) and achieved up to 1291 mg/L of biodiesel, a 40-fold rise compared to the BD...

Biofuel production in Escherichia coli: the role of metabolic engineering and synthetic biology

Applied Microbiology and Biotechnology, 2010

The microbial production of biofuels is a promising avenue for the development of viable processes for the generation of fuels from sustainable resources. In order to become cost and energy effective, these processes must utilize organisms that can be optimized to efficiently produce candidate fuels from a variety of feedstocks. Escherichia coli has become a promising host organism for the microbial production of biofuels in part due to the ease at which this organism can be manipulated. Advancements in metabolic engineering and synthetic biology have led to the ability to efficiently engineer E. coli as a biocatalyst for the production of a wide variety of potential biofuels from several biomass constituents. This review focuses on recent efforts devoted to engineering E. coli for the production of biofuels, with emphasis on the key aspects of both the utilization of a variety of substrates as well as the synthesis of several promising biofuels. Strategies for the efficient utilization of carbohydrates, carbohydrate mixtures, and noncarbohydrate carbon sources will be discussed along with engineering efforts for the exploitation of both fermentative and nonfermentative pathways for the production of candidate biofuels such as alcohols and higher carbon biofuels derived from fatty acid and isoprenoid pathways. Continued advancements in metabolic engineering and synthetic biology will help improve not only the titers, yields, and productivities of biofuels discussed herein, but also increase the potential range of compounds that can be produced.

Engineering of Bacterial Methyl Ketone Synthesis for Biofuels

Applied and Environmental Microbiology, 2012

We have engineered Escherichia coli to overproduce saturated and monounsaturated aliphatic methyl ketones in the C 11 to C 15 (diesel) range; this group of methyl ketones includes 2-undecanone and 2-tridecanone, which are of importance to the flavor and fragrance industry and also have favorable cetane numbers (as we report here). We describe specific improvements that resulted in a 700-fold enhancement in methyl ketone titer relative to that of a fatty acid-overproducing E. coli strain, including the following: (i) overproduction of ␤-ketoacyl coenzyme A (CoA) thioesters achieved by modification of the ␤-oxidation pathway (specifically, overexpression of a heterologous acyl-CoA oxidase and native FadB and chromosomal deletion of fadA) and (ii) overexpression of a native thioesterase (FadM). FadM was previously associated with oleic acid degradation, not methyl ketone synthesis, but outperformed a recently identified methyl ketone synthase (Solanum habrochaites MKS2 [ShMKS2], a thioesterase from wild tomato) in ␤-ketoacyl-CoA-overproducing strains tested. Whole-genome transcriptional (microarray) studies led to the discovery that FadM is a valuable catalyst for enhancing methyl ketone production.

Microbial engineering to produce fatty alcohols and alkanes

Journal of Industrial Microbiology and Biotechnology, 2021

Owing to their high energy density and composition, fatty acid-derived chemicals possess a wide range of applications such as biofuels, biomaterials, and other biochemical, and as a consequence, the global annual demand for products has surpassed 2 million tons. With the exhausting petroleum reservoirs and emerging environmental concerns on using petroleum feedstock, it has become indispensable to shift to a renewable-based industry. With the advancement in the field of synthetic biology and metabolic engineering, the use of microbes as factories for the production of fatty acid-derived chemicals is becoming a promising alternative approach for the production of these derivatives. Numerous metabolic approaches have been developed for conditioning the microbes to improve existing or develop new methodologies capable of efficient oleochemical production. However, there still exist several limitations that need to be addressed for the commercial viability of the microbial cell factory ...