Sucheta Dalal :Plant waste to sugar the Novozymes way
Sucheta Dalal

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Plant waste to sugar, the Novozymes way  

October 23, 2009


Novozymes, the largest manufacturer of industrial enzymes, has finally discovered what we have been looking for. More than twenty companies have been working on this technology but till date they have failed because they could not break through how enzyme can treat lignin. Novozymes has prepared an enzyme cocktail that can break down the fibrous material into glucose that can be converted into oil and plastics.
Billions of tonnes of cellulose (stems of trees, branches, weeds and biodegradable waste) that used to be converted into coal and crude under heavy pressure and temperature under Earth’s surface, is now readily available as a potential source of glucose. Under Earth’s surface, it gets converted into hydrocarbons. But now the new technology can convert it into sugars through enzymatic reactions.
All plant structures are composed of many-linked chains of sugar, cellulose and hemicellulose which are surrounded by lignin. Lignin is a glue-like carbon molecule that holds these sugar polymers together. Lignocellulosic material is the largest component of plant matter by weight. Both cellulose and hemi-cellulose are long chain polymers made up of individual sugar molecules.
The cellulose chain splits into glucose (a six carbon sugar known as ‘C6’) and hemi-cellulose breaks down into xylose (a five carbon sugar, known as ‘C5’). They can be easily converted to sugar through hydrolysis where they get hydrogen and oxygen. The molecular formula for glucose or fructose is C6H12O6 and table sugar or sucrose is C12H22O11. Though cellulose is found in greater proportions than hemi-cellulose, the relative amounts of each within a plant depends upon the kind of plant and its age.
Cellulose is associated with lignin and pentosans and resists biodegradation. That is the reason that why dead trees take several years to decay even in tropical rainforests. A typical waste lignocellulosic material contains less than half cellulose, most of the remainder consisting of roughly equal quantities of lignin and pentosans.
A combination of enzymes is needed to degrade this mixture. These enzymes are comparatively unstable of low activity against native lignocellulose and subject to both substrate and product inhibition. Consequently, although many cellulolytic enzymes exist and it is possible to convert pure cellulose to glucose using only enzymes, the cost of this conversion is excessive.
And now Novozymes is the first company that has demonstrated economical conversion of plant waste to sugar through enzymes. It is likely to make commercial quantities of the new enzymes and will be ready for volume production by next year. – Dhruv Rathi [email protected]

-- Sucheta Dalal