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Research Article

High-Yield Hydrogen Production from Starch and Water by a Synthetic Enzymatic Pathway

  • Y.-H. Percival Zhang mail,

    To whom correspondence should be addressed. E-mail: ypzhang@vt.edu

    Affiliation: Biological Systems Engineering Department, Virginia Tech, Blacksburg, Virginia, United States of America

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  • Barbara R. Evans,

    Affiliation: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America

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  • Jonathan R. Mielenz,

    Affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America

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  • Robert C. Hopkins,

    Affiliation: Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America

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  • Michael W.W. Adams

    Affiliation: Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America

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  • Published: May 23, 2007
  • DOI: 10.1371/journal.pone.0000456

Reader Comments (4)

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Enzyme costs

Posted by prm24 on 30 May 2007 at 14:43 GMT

The authors estimate $10/kg crude recombinant enzyme production costs. I am not in this field and have no experience on industrial levels, but given what minute quantities of various enzymes for lab use seem to cost (hundreds of dollars for sub-gram amounts), I am amazed it could be this low. I was hoping that people with experience using recombinant enzymes on an industrial scale could chime in. What techniques (expression system, growth media, purification scheme) are used to keep production costs so low..... What kind of drop in yield might you expect going from super pure sigma reagents to crude purifications for all enzymes in a 13 step pathway. I'm not saying it can't be done for the price the authors state, I'm just curious about the details.


RE: Enzyme costs

ypzhang replied to prm24 on 03 Jun 2007 at 13:54 GMT

Enzyme cost is an interest topic. In my personal view, the market is the most determinant drive force for its costs. Take cellulase an example, cellulase is produced by Trichoderma species for more than 20 years. After the discovery of Rut-30 (a super cellulase-producing strain), enzyme companies produce a lot of cellulases for some real applications. About 10 years ago, the cellulase production costs were $50-60 dollars per kg because of limited application. After DOE gave > 22 millions to Genencor and Novozymes for reducing enzyme cost for cellulosic ethanol production, current cellulose costs ranges 1-2 dollars/kg. They decrease cost through several factors: change carbon source from lactose to glucose (cheaper), increase fermentation titer (100 g proterin /L), adjust enzyme composition, etc.

About recombinant protein, should we purify it before use? The answer may be not. If we express a thermophilic recombinant protein E. coli, after expression we can increase temperature to denature the E. coli that we do not need. If we need protein purification, we are developing a new ultra-low-cost recombinnat protern purification method (lower than all existing method). Surely, high cell-density fermentation will be very important for protein production. I think that most of them are well-known industrial skills. Markets and money will drive the enzyme cost greatly. Thank of computer, DVD player, digital camera, etc.


RE: RE: Enzyme costs

ypzhang replied to ypzhang on 03 Jun 2007 at 14:01 GMT

In the regular lab level, protein expression level is very low because most time no one need such large amount. In additon, most biological science lab lacks the skill for high-cell density fermentation. I was trained as biochemical engineer. Fermenation is a basic skill. It is why we know some know-hows.