Genetically engineered bacteria (GEB) are small biological “factories” that can produce molecular compounds on a continuous basis. Advancements in genetic engineering and synthetic biology have enabled the use of GEBs in an increasing number of industrial applications.

Manipulating bacteria to create useful molecular compounds is not a novel realization to synthetic biologists. Scientists are able to manipulate bacteria to generate many different types of chemicals. Predominant chemical factories around the world harness the power of colonies of genetically engineered bacteria.

Simple diagram of a bacterium. Source: domdomegg/CC BY-SA 4.0

A GEB is a bacterium that can efficiently produce molecular compounds or heterologous proteins after being genetically modified. Genetically modifying bacteria began in the 19th century and by the end of the 20th century, modifying bacteria is widely accomplished by genetic engineering to efficiently produce compounds.

After decades of study and development, GEBs are now established in many industrial applications, such as the food industry, chemical synthesis and environmental protection. Escherichia coli, Lactobacillus and Salmonella are popular bacteria used to construct different GEBs or to be used as chassis tools. It is estimated that more than 50 bacteria species are used in scientific research and health care.

Bacteria make simple and inexpensive host organisms and have many expression systems that can be used for recombination and result in easy modification integration. Bacteria contain extra loops of DNA called plasmids in addition to their chromosomes; these plasmids can be swapped with one another in nature. This trait is one way that bacteria can undergo genetic modification, and genetic operation tools can be used to shear, splice and integrate desired genes and introduce them into chassis cells. The recombinant genes are transferred to desired products in this way or create new phenotypes in the bacteria.

Biofuel production basics

Bio-based fuel production is an emerging sector with future potential and business prospects as these methods are often cost-effective and may reuse waste compounds. Biodiesel is commonly derived from resources such as oil-bearing seed plants utilizing fungi, bacteria and blue-green algae. Biorefineries can use biomass to produce biofuels while minimizing environmental impact by reusing waste. Since biodiesel is biogenic, it is believed to not contribute to atmospheric emissions. Biodiesel is also degradable and can be blended with conventional diesel to be used in existing engines.

There are a variety of methods to generate biofuels, often split into four generations though these may be defined differently depending on the establishment.

• First generation: These biofuels are produced from edible energy crops such as oil-based, starch-based and sugar-based crops.
• Second generation: Biofuels are produced from waste products or from non-food raw materials grown specifically for biofuel production.
• Third generation: These biofuels are created using algae and are also known as algae fuel or oilage.
• Fourth generation: Combine genetically modified crops with genetically modified organisms using nonarable land to create biofuels.

Bloom of cyanobacteria in a freshwater pond. Source: Christian Fischer/CC BY-SA 3.0

Commercially available biofuels are predominantly first and second-generation and often use biomass grown explicitly for use in their production. Microalgae, macroalgae and cyanobacteria are commonly used as biomass feedstock in third-generation biofuels. Hand in hand with genetically modified bacteria are genetically modified crops. Modified crops are common fuel sources for bacteria in industrial applications.

Bacteria in biofuel production

Many problems result from the lack of industrially capable strains, and genetic modification of bacteria reduces those issues. Escherichia coli is the bacterium that is behind most cases of food poisoning in the U.S. but is of value in genetic engineering spheres as it can tolerate genetic changes well and is quite hardy. As a result, modifying E. coli has been studied with significant advancements in medicine, chemical and biofuel production.

In biofuel production, E. coli has been modified to consume sugar and secrete biodiesel. In fermentation vats, the engine-grade biodiesel created by the bacteria floats to the top without the need for distilling and purifying unlike when biodiesel is produced from algae.

Biofuel production is constrained by the available energy sources of biomass. Ideal bacterial strains can be manufactured that use available energy sources. For example, producing biofuel from lignocellulosic biomass requires a bacterial strain that can exploit pentose-rich and hexose-containing sugars. Many organisms used in fermentation cannot utilize pentose sugars and many that can do not yield desired end products or may create unwanted by-products.

To limit the impact on food sources, bacteria can be modified to secrete an enzyme that breaks down plant material to create sugar from cellulose that can then be consumed to make biodiesel. As efficiency increases, the required amount of farmland needed to produce biomass is reduced. In the future, waste materials could be more effectively utilized to generate fuel, whereas currently, biofuel created directly from crops grown for use in production is predominantly used.

[See also: Biofuel packs an energy density punch]

Bacteria, designed for productivity

Microbial strain development through genetic engineering has advanced the industrial application of bacteria significantly. Microbes intrinsically found in various habitats naturally produce bioactive compounds that are used as drugs, fuels and important chemicals. The increase in the number of whole-genome sequenced organisms has improved metabolic pathway manipulation, which has increased the production efficiency of chemicals. Additional research and development will open the doorways to further advancements in bacteria design.

About the author

Jody Dascalu is a freelance writer in the technology and engineering niche and works as a business analyst in the manufacturing industry. She studied in Canada and earned a Bachelor of Engineering. As an avid reader, she enjoys researching upcoming technologies and is an expert on a variety of topics.