Category Archives: Advances in Biochemical Engineering/Biotechnology

Application of Ethanol Design Scheme to Other Commodity Products

Petrochemicals and petroleum-based products such as plastics are widely integrated into our lifestyles and make a major, irreplaceable contribution to virtually all product areas. Increasing petroleum costs have provided an opportunity for a number of renewable bio-based chemicals or plastics, in addition to the bio-based fuels, to become economically competitive. How­ever, full commercialization of renewable commodity chemicals to replace the […]

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Flowsheeting

Flowsheeting programs, e. g. Aspen Plus, HYSYS and ChemCad, may be used to perform rigorous material and energy balance calculations, with the use of detailed equipment models, to determine the flow rates, composition and energy flow for all streams in the process. Because of their flexibility, the programs have many advantages when comparing different process configu­rations or scenarios in terms […]

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Sugar Transport

The transport of pentose sugars in S. cerevisiae occurs through hexose trans­porters [80,81], albeit with an affinity one to two orders of magnitude lower than for hexose sugars [47,82]. Therefore, pentose transport was early con­sidered a rate-controlling step for ethanolic pentose fermentation [47]. Nev­ertheless, a metabolic control analysis study demonstrated that transport controlled xylose conversion only in strains with high […]

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Baker’s Yeast (5. cerevisiae) as a CBP Host

Despite the status of S. cerevisiae as a proven industrial microorganism, con­ferring the ability to rapidly convert pretreated cellulose to ethanol is a daunt­ing proposition. Apart from essential traits, such as high ethanol yield and productivity, industrial strains need to concurrently ferment both hexoses and pentoses under robust industrial conditions that require minimum nutri­ent requirements and high ethanol and inhibitor […]

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Kinetic Characteristics of Recombinant Strains

Detailed kinetic studies have been reported in the literature for several re­combinant strains of Z. mobilis from NREL capable of utilizing both glucose and xylose. The initial evaluation by Zhang et al. [10] involved the batch culture growth of the strain CP4 (pZB5) on medium containing 25 g L-1 glu­cose and 25 gL-1 xylose. Batch and continuous culture studies on […]

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Direct Funding Programs in the USA

As seen in the review of major biofuel producers, a common policy instru­ment used to support the industry is direct government program funding, in the form of contracts, loans, grants, or fiscal guarantees. It is difficult to evaluate the effectiveness of direct funding by comparing different countries, where synergistic policies (such as renewable fuel mandates, excise tax ex­emptions, etc.) or […]

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Industrial Pentose-Fermenting Strains

Metabolic engineering strategies for pentose fermentation are developed to fi­nally generate strains that ferment pentose sugars to ethanol under industrial conditions, which may include suboptimal pH and an array of compounds which inhibit cellular metabolism. Industrial strains of S. cerevisiae, including baker’s yeast, generally out-compete most other microorganisms with regard to the properties required in industrial ethanol production [9,10,133-135], including […]

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Hydrogen Production

Biological conversion of biomass to hydrogen either proceeds through photo­fermentation or dark fermentation. In dark fermentation the yield is only 10-20% of the potential hydrogen amount that theoretically can be de­rived from organic matter ([7] and Westermann P, J0rgensen B, Lange L, Ahring BK, Christensen CH (2007) Int J Hydrogen Energy (accepted for pub­lication)). Typical hydrogen yields are from 0.52 […]

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Performance of the Thermostable Enzymes at Lower Temperatures

The performance of the thermostable enzymes at a lower temperature, the 35 °C commonly used in SSF, was compared. The T. reesei deletion strains produced only low amounts of background cellulase activities, mainly due to the presence of native EGIII (Cel12A) and EGV (Cel45A). However, the deletion strains used for the production of thermoenzymes produced some hemicellulases. For practical use, […]

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