Wednesday, January 26, 2011

Farmers now delivering biomass to POET's Project LIBERTY storage site

A news from Renewable energy "Farmers now delivering biomass to POET's Project LIBERTY storage site ", indicating Poet is making progress on cellulosic ethanol. Hopefully it is not just a trial or testing!

Wednesday, January 19, 2011

Heterogeneous azeotropic distillation with n-hexane

Heterogeneous azeotropic distillation is a widely used technique for separating binary azeotropic mixtures into their components. To produce pure ethanol,  heterogeneous azeotropic distillation using hexane instead of benzen as the entrainer has been developed recently because  n-hexane is a common compound found in gasoline and any trace amount of hexane in the anhydrous ethanol will not be a problem for its subsequent use as a fuel. The composition of the ternary azeotrope determined by numerical interpolation was reported as  0.105, 0.236 and 0.658 mole fraction of water, ethanol, and n-hexane, respectively, and the temperature is 329.21 K.

The heterogeneous azeotropic distillation with n-hexane can produce pure ethano with relatively low energy input.

Sunday, January 16, 2011

The opportunities of enzyme expressed grain

Successful expression of enzymes in corn grains will bring the following opportunities for bioethanol production in low cost:

1. Recover suars from DDGs corn fibers by enzymatic hydrolysis using extracted proteins from exzyme expressed corn grains.
2. Mix exzyme expressed grains with pretreated biomass to reduce external hydrolytic enzymes.

Currently, the technology for such a expression is avaible; therefore it is expected such cost effective applications will integrate into bioethanol production.

Thursday, January 13, 2011

Vacuum fermentation and distillation

It is known that high ethanol concentrations (10% v/v) were inhibitory to the industrial yeast strains and would reduce the yeast growth and cell density in the high solids mash. However, high slurry solids saccharification and fermentation are right direction for cost effective production of fuel ethanol. To overecome the challenge, vacuum feremtation and vacuum distillation can be applied to remove ethanol produced during SSF. As a result,the ethanol concentration was maintained as negligible during the entire fermentation process, which can lead to high ethanol productivity.Combining hydrolytic enzyme hydrolysis and SSF under a vacuum allows the integration of all four unit operations (liquefaction, saccharification, fermentation and distillation) into one single step, which eliminates both substrate (glucose) and product (ethanol) inhibition of the yeast and allow very high slurry solids (~40%) ssacharification and fermentation.

The higher slurry solids and removal of water during vacuum distillation will also result in higher percentage of stillage solids at the end of the fermentation, which can be sold directly as wet grains without any need for centrifugation and thin stillage evaporation to remove water, therefore to reduce operational cost to a great extent.

Tuesday, January 4, 2011

In planta expression of biomass cell-degrading enzymes: the solution to cheap sugar for biorefinery

One of the approaches to utilize lignocellulosic biomass as feedstocks for biorefibery is through biological conversion. Currently, an efficient, rapid, and complete enzymatic hydrolysis of biomass using low enzyme loadings is still one of the major technical and economical bottlenecks in this process because of the lack of low cost pretreatment technology as well as high cost of enzymes. Since lignocellulosic biomass is composed of a matrix with multiple intertwined biopolymers (cellulose, hemicelluloses, lignin and extractives), it requires several different classes of enzymes in large quantities to efficiently release fermentable sugars. As a result, it is necessary to produce different classes of enzymes individually in a large scale and then make cocktails for biomass hydrolysis. Because of the high cost and limited capacity for producing these enzymes through fermentation, today, it is still a big challenge to develop an efficient enzyme production system for rapid and less expensive biomass depolymerization.

However, all these enzymes required for biomass enzymatic hydrolysis are produced naturally by a range of microbial species including bacteria and fungi. Many cell wall-degrading enzymes have been isolated and characterized and more are still not uncovered. Availability of genome sequences of Trichoderma reesei and other organisms have increased inventory of enzymes for biomass utilization.

Plants have already been used as a “factory” in industry to produce enzymes and other proteins, carbohydrates, lipids, industrial polymers and pharmaceuticals. Successful technology is available for plant genetic transformation, farming of transgenic crops and harvesting, transporting and processing the plant matter. Therefore, expression of all different classes of cell wall-degrading enzymes  into plants provides great opportunity for developing biomass-specific enzyme cocktails, which will create a low sugar platform for biorefinery.

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