ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Making Fuel from Cellulose – A Promising Future

Updated on July 3, 2013

Cellulosic Ethanol – A Magical Biofuel

Due to the rapid rate of depletion of our natural reserves of oil and natural gas, various government agencies and private industries are struggling hard to invent technologies which can convert cellulosic material into motor fuels, in a cost effective manner. Cellulose has been made the target as; it is the most abundant organic compound present on our planet Earth. It forms the structural component of all the green plants. It is rich in glucose, which can be easily converted to sugars and fermented to produce “cellulosic ethanol” – the magical Biofuel. And above all, if we are able to produce this biofuel at a reasonable cost and meet the demands of the entire world, it can act a renewable source of energy, as it is synthesized from never ending raw materials like, non-edible parts of plants, grasses, wood, miscanthus, sugarcane bagasse, sorted municipal waste, etc.

Technology behind Cellulosic Conversion

Even though the conversion of cellulose into sugars and fermentation into ethanol (biofuel) looks to be simple on board, we have to cross many hurdles before we are able to device a user-friendly technology which can convert cellulose into cellulosic ethanol. Currently, cellulose conversion technologies have been broadly classified into two categories, which are, thermal and biochemical (enzyme based processes) technologies. Under enzyme based biochemical processes, the bonds between the sugars are broken with the help of microbe-made enzymes. The enzymes capable of breaking these bonds are known as glycoside hydrolases, or GHs. The enzymes of various bacteria like Saccharophagus degradans, Clostridium thermocellu and Caldanaerobius polysaccharolyticus, are being studied for their efficiency in conversion of cellulose to ethanol.

What makes cellulosic conversion difficult?

Currently, even though the raw material required for the conversion is very abundant, the use of this cellulose conversion technology is very limited, as it is highly expensive. The main reason behind this is that, apart from cellulose the cell walls also contain abundant quantities of hemicellulose. The microorganisms are generally able to convert cellulose into sugars, but fail to make efficient use of hemicellulose. The bonds which join the sugar units of cellulose are different from those which join the sugar units of hemicellulose. In cellulose, the glucose units are linked together with the help of β-1,4-glycosidic linkages, whereas in some feedstock, hemicellulose mainly consists of β-1,4-linked xylose backbones with arabinose side chains. In some cases, the hemicellulose of feedstock also consists of larger variety of sugars, including galactose and mannose. These sugars exist in different forms of mannans. The presence of such complex strong bonds makes it difficult for the microbes to produce ethanol in comparable quantities.

Amongst the different varieties of mannans found in nature, some are made up of a linear chain of mannose residues linked with the help of β-1,4-linkages. These mannans include glucomannan, galactomannan, and glucogalactomannan. The galactose residues are further linked to the mannan backbone with the help of α-1,6-linkages in galactomannans or glucogalactomannnans. Hence, hydrolysis of mannans to its component sugars is a very crucial step and requires endo-1,4-β-mannanases enzymes. These enzymes can hydrolyze the backbone linkages and produce short-chain manno-oligosaccharides. These are further degraded with the help of 1,4-β-mannosidases to generate monosaccharides. Hence, only the microbes containing the enzymes capable of breaking the backbone of mannans can prove to be economically useful.

Can Caldanaerobius polysaccharolyticus, the “garbage bug” produce biofuel economically?

The discovery of Caldanaerobius polysaccharolyticus by Rod Mackie in 1993 has come up as a solution to the above mentioned problem. It is a thermophilic bacterium and was isolated from the garbage dump of a canning plant. When the genome of this bacterium was sequenced and analyzed, it was found that its genome possessed a gene cluster containing both hydrolytic enzymes and enzymes key to the pentose-phosphate pathway. Man5A enzyme encoded by its genome showed mannanase/endoglucanase activities. The recently discovered man5B gene products in Caldanaerobius polysaccharolyticus, have also shown the hydrolytic activity on mannan-containing polysaccharides. As these genes involved in the conversion are clustered together in a single place within the genome, it makes the job of genetic engineers easier.

Another advantage associated with this bacterium is that the enzymes of this bacterium can tolerate high temperatures (as high as 70 degrees Celsius) as Caldanaerobius polysaccharolyticus is a thermophilic bacterium. According to the current practice, the biofuel fermentation is carried at 37°C and this temperature favors the growth of multiple microbes which can contaminate the fermentation vats easily. However, as Caldanaerobius polysaccharolyticus can be used at very high temperatures, the risk of contamination is negated.

Future of Cellulosic Ethanol

Cellulosic ethanol has the potential to act as a fuel which can power our vehicles and perform multiple activities. Hence, research promoting the design of convenient technology involving Caldanaerobius polysaccharolyticus bacterium has a promising future. It will not only clear huge amounts of plant waste thrown in the landfills but also generate a highly useful product for day-to-day use.

My Sources of Information

1. Brief: Converting cellulose into ethanol and other biofuels, retrieved from

http://www.ethanolacrossamerica.net/pdfs/CelluosicEthanolssueBrief_April2010.pdf

2. Han, Y., Agarwal, V, et al. (2012). Biochemical and Structural Insights into Xylan Utilization by the Thermophilic Bacterium Caldanaerobius polysaccharolyticus, The Journal of Biological Chemistry, 287, 34946-34960.

3. Han, Y., Dodd, B., et al. (2010). Comparative Analyses of Two Thermophilic Enzymes Exhibiting both β-1,4 Mannosidic and β-1,4 Glucosidic Cleavage Activities from Caldanaerobius polysaccharolyticus, J. Bacteriol. 192,16 4111-4121.

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)