Starch utilization process

2 ETHANOL PRODUCTION FROM STARCHY BIOMASS 8.2.1 Starch Utilization Process 

2 Yeast Cell-Surface Engineering System for Biomass Utiiization 

Yeast cell-surface engineering has been established to display enzymes, functional proteins, antibodies, and combinatorial protein libraries (Kondo and Ueda, 2004). The cell surface is a functional interface between the inside and outside of the cell allowing some surface proteins to extend across the plasma membrane, while others are bound by non-covalent or covalent interactions to the cell surface components. For anchoring surface-specific proteins, yeast cells have molecular systems to confine 

3 Ethanol Production from Starchy Biomass Using Amyiase-Expressing Yeast 

Surface expression of amylolytic enzymes was initiated by the pioneering work of Murai et al. (1997) who reported a strategy for development of recombinant Sa. 

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Chamberlain, E. K. 1996. Characterization of heated and thermally processed cross-linked waxy maize starch utilizing particle size analysis, microscopy and rheology. M. S. Thesis, Cornell University, Ithaca, NY. 

Processes and products of m. differ systematically from - starch hydrolysis products that are obtained by splitting the glucosidic linkages with acids and/ or enzymes. Those products comprise the largest group in starch utilization. 

Starch production, processing and sale in 1998 surpassed 7.7 x 10 mt with an entire turn over of 9.0 X 10 DM. Utilization is diveded by 55% for food and 45% for nonfood purposes. The average... 

Hydroxylall l Starch Ethers. Starch hydroxyethyl ethers with a degree of substitution (DS) of 0.05—0.10 ate produced in various ways, but usually their preparation begins at the end of the wet-milling process, utilizing a high soHds-starch suspension. The ether modification of ungelatinized starch is filterable and can be produced economically in a pure form. 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

A slurry of the starch is cooked in the presence of a heat-stable bacterial endo-a-amylase. The enzyme hydrolyzes the a-l,4-glycosidic bonds in pregelatinized starch, the viscosity of the gel rapidly decreases, and maltodextrins are produced. The process may be terrninated at this point. The solution is purified and dried, and the maltodextrins are utilized as blandtasting functional ingredients in dry soup mixes, infant foods, sauces and gravy mixes, etc. 

A cost efficient way to utilize wheat in ethanol production has been developed by researchers from Greece and the U.K. This process splits the grain into separate components, separating out the nonfermentable solids, and then uses a group of enzymes to ferment the proteins and starches using a single liquefaction and saccharification step. 

Steeping and wet-milling processes are also utilized to separate soluble compounds from com. One process involves removal of soluble starch and protein from com by steeping com in a warm sulfurous acid solution for about one to two days. The undissolved com solids are then coarsely wet-milled and processed to collect the oil-containing germ for com oil production. Also, for more enzyme-resistant cellulose biomass, sulfuric acid or hydrochloric acid can be used to digest the cellulose polysaccharide into fermentable molecules. 

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