News and Trends

Qantas made the world's first dedicated biofuel flight between the United States and Australia. Qantas QF96 flew from Los Angeles to Melbourne over the weekend. The 15-hour trans-Pacific flight operated with approximately 24,000 kg of 10% biofuel blend, saving 18,000 kg in carbon emissions.

Fuel for the flight was produced from Brassica carinata, a non-edible industrial mustard seed, by AltAir Paramount LLC using Honeywell UOP's Renewable Jet Fuel process technology. The seeds were developed by Agrisoma Biosciences. Qantas established a partnership with Agrisoma to promote Carinata as a crop for Australian farmers, specifically as a renewable feedstock for making commercial aviation biofuel.

Using carinata-derived biofuel can reduce carbon emissions by eighty percent compared to traditional jet fuel. The ten percent biofuel blend used on the flight will therefore see a seven percent reduction in emissions on this route compared to normal operations.

Research and Development

Yarrowia lipolytica is a common biotechnological platform for the production of lipids, the preferred feedstock for the production of biofuels and chemicals. To reduce the cost of microbial lipid production, inexpensive carbon sources should be used, such as lignocellulosic hydrolysates. Unfortunately, lignocellulosic materials often contain toxic compounds and a large amount of xylose, which cannot be used by the yeast.

The team of Xochitl Niehus from the Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco in Mexico engineered the yeast to use xylose as a carbon source for the production of lipids. The team achieved this by overexpressing native genes of Y. lipolytica.

The lipid content was further increased in the yeast by overexpressing the inserted genes involved in the production of lipid precursors from xylose in Y. lipolytica. The engineered strains were able to produce high yields of lipids on a xylose-rich agave bagasse hydrolysate inspite of the presence of toxic compounds.

This study shows the potential of metabolic engineering in reducing costs by allowing lipid production from inexpensive feedstock.

Stanford scientists have found a new type of cellulose, called pEtN, in Escherichia coli.

This study, led by Lynette Cegelski, was originally aimed to investigate the matrix of slime-like materials that surrounds microbes and protects their communities. In this latticework, the team found a modified form of cellulose. It had been missed by previous research since traditional lab techniques involve chemicals that destroyed the matrix.

This new form of cellulose had properties that could make it an improvement over other sources to produce ethanol for fuels. The modified cellulose doesn't form crystals and is relatively soluble in water, which the researchers think could make it easier and significantly less expensive to convert into glucose for producing ethanol.

Cegelski and her team then explored the structure of the new cellulose as well as the genes and molecules involved in making it. Cegelski is now trying to introduce these genes into plants.The team is also exploring the mechanical properties of pEtN compared to other forms of cellulose and to search for other applications.

The formation of by-products, mainly acetone, in the acetone–butanol–ethanol (ABE) fermentation significantly affects the yield. The team led by Chao Wang of Nanjing Tech University in China genetically-engineered Clostridium acetobutylicum to eliminate acetone production. The team also altered ABE fermentation to isopropanol–butanol–ethanol (IBE).

After introduction of secondary alcohol dehydrogenase into C. acetobutylicum XY16, the engineered XY16 completely eliminated acetone and converted it to isopropanol, indicating great potential for the production of IBE mixtures. Under the optimal pH level of 4.8, the total IBE production was significantly increased from 3.88 to 16.09 g/L, with final yields of 9.97, 4.98 and 1.14 g/L for butanol, isopropanol, and ethanol, respectively.

Furthermore, calcium carbonate could be both a buffer and activator for NAD kinase (NADK). Supplementation of calcium carbonate further improved IBE production to 17.77 g/L with 10.51, 6.02, and 1.24 g/L of butanol, isopropanol, and ethanol, respectively.

Energy Crops and Feedstocks for Biofuels Production

A team at the University of Nebraska–Lincoln is exploring sweet sorghum ethanol as a future income source for western Nebraska.

Sweet sorghum is a cultivar of sorghum developed for the harvest of juice. Due to its high sugar content and stability in drought, researchers deemed it as a potential ethanol feedstock crop on non-irrigated farmland in western Nebraska. In this case, the sugar syrup from sweet sorghum stalks would be fermented to make ethanol.

For sweet sorghum to compete for ethanol production, the team found that it must be more lucrative than corn for farmers to produce and must be more economical than ethanol plants to process. Another consideration which would increase the potential of sweet sorghum for ethanol is an increase in yields.

Currently, a separate research project aims to improve sorghum as a sustainable source for biofuel production.

The development of fast-growing hardwood trees as a source of biomass for biofuel production requires a good understanding of the plant cell wall structure and mechanisms that underlie the recalcitrance of woody biomass. Downregulation of the GAUT12.1 gene in poplar (Populus deltoids) was reported to result in improved biomass saccharification, plant growth, and biomass yield.

To further understand GAUT12.1 function, the team of Ajaya K. Biswal from the University of Georgia overexpressed the black cottonwood (Populus trichocarpa) PtGAUT12.1 gene in poplar. Overexpressing PtGAUT12.1 in poplar resulted in a nearly complete opposite biomass saccharification and plant growth phenotype to that of PdGAUT12.1-knockdown (KD) lines. This included significantly reduced glucose, xylose, and total sugar release, plant height, stem diameter, and overall total aerial biomass yield compared to controls. Total lignin content was unaffected by the gene overexpression.

The combined data from P. deltoids, PtGAUT12.1-overexpressing lines and PdGAUT12.1-knockdown lines establish GAUT12.1 as a recalcitrance- and growth-associated gene in poplar.

Biofuels Processing

Researchers in Canada claim to have found a simpler, cleaner way to produce fuel from waste materials such as sewage.

Currently, biowaste is converted into biofuel with a two-step process. Biomass is converted into biocrude oil with a chemical and thermal process and the second stage is refining, where hydrogen is added under high pressure and heat, serving to remove contaminants such as sulfur, nitrogen and oxygen. This two-step process is expensive and energy intensive. Moreover, carbon waste is left over in the form of char and CO2 emissions.

To solve this, scientists from the University of Calgary have developed a process that simultaneously produces and upgrades bio-oil in one step and without the need for high pressures. The process uses methane instead of hydrogen for the purification process.

The key to this breakthrough is a catalyst the researchers developed at Canadian Light Source, which reacted with methane, causing it to release hydrogen. The researchers then coated the catalyst, called HZSM-5, with different materials to improve its ability to react with methane.

Initial tests with the new catalyst have shown that it is a more efficient method of producing biofuels from waste, which also leads to better quality, more stable biofuel with significantly lower greenhouse gas emissions.

Biogas production from lignocellulosic biomass is considered challenging due to the recalcitrant nature of the biomass. The team of Daniel Girma Mulat from the Norwegian University of Life Sciences applied steam-explosion (SE) pretreatment (210 °C and 10 min) to reduce the recalcitrance of birch. The team also performed bioaugmentation, the addition of other cultured microorganisms. They added Caldicellulosiruptor bescii to the anaerobic digestion (AD) to enhance methane production from steam-exploded birch.

The combined SE and addition of C. bescii enhanced methane yield by up to 140% compared to untreated birch, while SE alone contributed to the major share of methane enhancement by 118%. The best methane improvement was observed in bottles fed with pretreated birch and with lower dosages of C. bescii. The maximum methane production from steam-exploded birch with dosages of C. bescii increased significantly compared to the yield from untreated birch.

The bioaugmentation was effective for increasing the initial methane production rate of pretreated birch, yielding 21–44% more methane than pretreated birch without bioaugmentation.

These results demonstrate the potential of combined SE and bioaugmentation for enhancing methane production from lignocellulosic biomass.