Xylooligomers are strong inhibitors of cellulose hydrolysis by enzymes

It has been known that xylooligomers are  the inhibitors to enzymatic hydrolysis. An customized enzyme cocktails have to be developed and applied on specific biomass substrates. Here are two recently published papers reported their research results on this issue.

•  "Supplementation with xylanase and b-xylosidase to reduce xylo-oligomer and xylan inhibition of enzymatic hydrolysis of cellulose and pretreated corn stover".
•  "Hemicellulases and auxiliary enzymes for improved conversion of lignocellulosic biomass to monosaccharides".

The dominating factor for biomass cellulose accessibility to external enzymes:

To improve biomass cellulose accessibility to external enzymes, pretreatment is often required, which seems to plat the following roles depending on the processing conditions:

• lignin or hemicellulose removal
• destroy cellulose crystal structure,
• open channels/cell wall pores
• increase cellulose surface exposure.

Since enzymatic hydrolysis follows the tunneling mechanism: eroding glucose from the inside of cell wall to the outside. Therefore, the pores or channels in cell wall are the dominant factor for the efficiency of enzymatic hydrolysis, i.e. control the rate of diffusion/transport of enzymes and sugar dissolution.

Size reduction by mechanical milling before themo/chemical pretreatment is the worst scenario although the surface area are improved.

Direct one-step conversion of ligninocellulosic biomass to hydrogen-enriched biofuel

The common ways for thermal conversion are fast pyrolysis and hydrothermal liquefaction.

·         The bio-oils obtained by fast pyrolysis are highly oxygenated complex mixtures, which are viscous, corrosive, and relatively unstable. The high contents of water and oxygenated compounds lead to the low HHV and the significant change of the combustion characteristics. They are not miscible with petroleum-based liquids. There is no efficient route for the upgrading needed to produce a motor fuel.

·         The bio-oils obtained by hydrothermal liquefaction are a complex mixture of ketones, aldehydes, phenols, alkenes, fatty acids, esters, aromatics, and nitrogen-containing heterocyclic compounds with high oxygen content and low heating value.

Direct One-Step Conversion of Lignin to Hydrogen-Enriched Biofuel involves in using solvent as the reaction medium and hydrogen donor with/without other catalysts, which can result in gasoline-like hydrocarbon product with high heating value and low char.

Promising New Accomplishments by Biofuel Vehicles

Written by Alan Parker, an active blogger out of New York City whose writing covers green technology, the environment, and the great outdoors.  You can follow him on Twitter @AGreenParker.

It isn't news to anybody that our oil supplies are disappearing rapidly, forcing car companies to develop new technologies that harness the power of alternative energy sources. Although most companies have been working on electric cars, several have also been dabbling in biofuels like ethanol, as a main fuel source for combustion engines. In order to demonstrate the effectiveness of biofuels and increase support for them, some independent research teams have succeeded in some exceptional feats with biofuel vehicles of their own. These accomplishments are showing that greener forms of energy can be used in a practical and effective way to eliminate our reliance on oil and make the environment a healthier place.

Cross-Continental Journeys
At the end of 2010, the first ever ground-based trans-Antarctic expedition was completed using only biofuels. The vehicle, called the Bio-inspired Ice Vehicle or BIV, was funded by biofuel advocate Winston Wong and is the world's first vehicle to complete a trans-Antarctic expedition using this type of power. The BIV was engineered to not only display the potential of alternative energy, but also to stand up to some of the harshest conditions on the planet while carrying researchers across an entire continent.

Setting Land Speed Records
A man named John Petsche set out to modify a Kawasaki motorcycle, aiming to create a vehicle that ran on an alternative fuel source, wasn't complicated or costly, and was designed for fuel efficiency. His result? A homemade motorcycle powered by biofuel. The bike set a land speed record for the 350cc alternative fuel motorcycles at the Loring Timing Association in Maine. The most astounding thing is that John Petsche's motorcycle was built using parts already in existence. Therefore, it should be a simple task for manufacturers to replicate and possibly improve upon the design for mass manufacture.

Distance Records in the Sky
It isn't only land vehicles that are making use of biofuels. Airlines are now beginning to look for alternative means of powering their planes. In fact, Finnair recently set a record for the longest commercial flight powered by biofuel, over 900 miles. Despite this incredible achievement, the airline openly admits that, since biofuel-powered air travel is still in its infancy, it isn't financially practical to convert biofuel just yet. However, they are continuing to experiment with it in hopes of reducing their impact on the environment.

When speaking of the grounds for creating the BIV to cross Antarctica, Winston Wong said that it was necessary to "do something that people can take notice [of] and say this is the future, the future of human endeavor” in an effort to reduce harm to the planet. The teams involved in the efforts above evidently placed stock in that same way of thinking, selecting rigorous ways to test different forms of alternative power. If we combine each of these cleaner energy forms and forward ideas, it is possible that we could soon see the beneficial impact that biofuels will have on our nation.

What is next of biofeuls and biochemicals?

Recently I have been in AIChE annual meeting at Minneapolis, MN. There I sensed a different atmosphere compared to what I felt last year: Less attendance and pessimistic in biofuels.

Indeed, in the past twenty years, DOE and other government agents spent tons of money to support technology development in biofuel production from biomass. People are expecting a sun-rising industry like IT in the past to boost the economy. Therefore, green technology once became a hot green waves hitting every aspects of people’s life, especially for biofuels. Unfortunately, the current dominant technologies claimed in patents and highlighted for biofuel production from biomass have actually been existing there for hundreds of years; none of them seems to solve the cheap sugar problem. Therefore, some anti-biofuel people even anticipate that there would be no biofuels in the next 20 years.

It is true that at least cellulosic bioethanol will be dead if these technologies continue to control the government funding for 10 years. It really needs game-changing technology. Among all of the highlighted technologies, Agrivida technology recently stands out from nowhere and looks like a real solution for cheap sugar production from if it works as it claims. Therefore, hope is still shining somewhere as long as creativity is alive.

In addition, more interests and attention are shifting toward hydrocarbon fuel production from lignocellulosic biomass.  And more value-added biochemicals are being produced from biomass although not heavily funded by government funding.  Although a lot of uncertainty still exists for biofuels and biochemicals, one thing that never changes is that they are from renewable resources. Biodegradable materials and chemicals may become leading green products in the near future.

Corn fiber as a raw material for hemicellulose and ethanol production

Com fiber, a byproduct of the wet milling process, has shown to be a substrate of particular interest due to its abundance, ready availability and low value. Corn fiber is primarily composed of the outer seed covering or pericarp of the kernel, along with adherent starch with typicallyl 20% xylose and 10% arabinose in the form of arabinoxylan, 18-24% cellulose and 20% starch although its apparent composition varies considerably according to its source and the method of analysis. As estimate, ethanol yields from com could be increased by approximately 10% if the constituent sugars of corn fiber could be efficiently utilized. Since the xylan in seed fiber is highly branched with arabinose and may cross-links with phenolic acids, GH 10 xylanase and ferulic acid esterases are suggested to supplement for enzymatic hydrolysis.