Feedstocks for ethanol manufacture Across beverage and fuel applications, which raw materials are used as substrates for industrial ethanol production?
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AStarch-rich materials (e.g., corn, wheat, cassava) after saccharification
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BCane juice, molasses, or sugar beet juice (readily fermentable sugars)
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CLignocellulosic residues from wood or processed wood (after pretreatment/hydrolysis)
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DAll of the above
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EOnly pure glucose solutions produced synthetically
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Substrate choice determines the process route and cost structure in ethanol production. Fermentable sugars may be available directly (sucrose sources) or generated by pretreating and hydrolyzing polymeric carbohydrates.
Given Data / Assumptions:
- Industrial processes use sugars derived from starch, sucrose, or cellulose/hemicellulose.
- Different pretreatments are required depending on feedstock.
Concept / Approach:Starch must be liquefied and saccharified (alpha-amylase, glucoamylase). Sucrose streams like cane juice or molasses can be fermented after clarification. Lignocellulosics (wood, ag residues) need pretreatment and enzymatic hydrolysis to yield hexoses and pentoses for fermentation.
Step-by-Step Solution:
Map each option to a known industrial route (starch-to-ethanol, cane-to-ethanol, cellulosic ethanol).Confirm that each can yield fermentable sugars suitable for ethanologens.Conclude that all listed feedstocks are valid for ethanol production.Verification / Alternative check:Commercial plants operate on corn (starch), sugarcane (sucrose), and pilot/commercial facilities on cellulosics, validating all routes.
Why Other Options Are Wrong:
- “Only pure glucose”: unnecessarily restrictive and not representative of industry.
Common Pitfalls:Ignoring pretreatment needs for lignocellulosics; assuming identical yields and inhibitors across substrates.
Final Answer:All of the above