把微生物改造成高效细胞工厂时，代谢工程通常采用哪些策略？
Which strategies does metabolic engineering typically use to turn microbes into efficient cell factories?
常用框架是推-拉-阻：上调前体供应形成推力，增强目标途径关键酶或引入高活性异源酶形成拉力，敲除或弱化竞争性支路减少流失。与之配套的是辅因子与能量平衡，例如调整 NADPH 与 NADH 的再生途径以匹配目标反应的还原力需求，以及控制乙酰辅酶 A 与 ATP 的供给。由于中间体积累常带来毒性和代谢负担，工程上还使用动态调控开关、群体感应控制的分阶段表达和途径酶的空间共定位。最后需要在发酵条件下迭代优化并借助基因组尺度模型指导靶点选择。
A common framework is push-pull-block: increase precursor supply to push flux, strengthen key pathway enzymes or add highly active heterologous ones to pull it, and delete or weaken competing branches to block losses. This is paired with cofactor and energy balancing, for instance retuning NADPH and NADH regeneration to match the reductive demand of the target reaction and managing acetyl-CoA and ATP supply. Because accumulating intermediates cause toxicity and metabolic burden, engineers add dynamic regulatory switches, quorum-sensing staged expression and spatial co-localization of pathway enzymes. Finally, targets are refined iteratively under real fermentation conditions with guidance from genome-scale models.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Nielsen, Keasling,《Engineering Cellular Metabolism》,Cell,2016 (DOI: 10.1016/j.cell.2016.02.004)
Nielsen, Keasling, 'Engineering Cellular Metabolism', Cell, 2016, DOI: 10.1016/j.cell.2016.02.004
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1016/j.cell.2016.02.004
#代谢工程 #细胞工厂 #辅因子平衡 #动态调控
用工程酵母半合成青蒿素前体，为什么被视为生物制造的里程碑？
Why is semisynthetic production of an artemisinin precursor in engineered yeast seen as a milestone in biomanufacturing?
青蒿素原本依赖从黄花蒿中提取，产量受种植面积和年际波动影响，价格不稳。研究者在酿酒酵母中重构甲羟戊酸途径以增强法尼基焦磷酸供应，引入青蒿的紫穗槐二烯合酶和细胞色素 P450 CYP71AV1 等基因，把发酵产物青蒿酸滴度提高到二十五克每升级别，再经化学光氧化转化为青蒿素。这一工作证明多基因异源途径可以在工业规模上稳定运行，把植物次生代谢产物的供应从农业条件中解耦，也成为后续萜类、生物碱等天然产物生物制造的模板。
Artemisinin was originally extracted from Artemisia annua, so supply and price fluctuated with planting area and season. Researchers rebuilt the mevalonate pathway in Saccharomyces cerevisiae to boost farnesyl pyrophosphate supply, introduced plant genes including amorphadiene synthase and the cytochrome P450 CYP71AV1, and raised fermentation titres of artemisinic acid to the twenty-five grams per litre range before converting it to artemisinin by chemical photooxidation. The work showed that a multigene heterologous pathway can run reliably at industrial scale, decoupling a plant secondary metabolite from agricultural conditions, and it became a template for biomanufacturing of other terpenoids and alkaloids.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Paddon CJ 等. High-level semi-synthetic production of the potent antimalarial artemisinin. Nature (2013) 496:528-532
Paddon CJ et al. High-level semi-synthetic production of the potent antimalarial artemisinin. Nature (2013) 496:528-532
#青蒿素 #半合成 #酿酒酵母 #萜类途径
工业发酵有哪几种操作模式，各自适合什么产品？
What operating modes are used in industrial fermentation, and what products suit each?
分批发酵一次性投料，操作简单、染菌风险低，适合周期短或与生长耦联的产品；补料分批在过程中按需补加碳源等底物，可避免高浓度底物抑制并延长产物合成期，是抗生素、重组蛋白和酵母生产的主流方式。连续发酵持续进料并等速排出料液，能长期维持稳态高产率，适合乙醇、单细胞蛋白等低附加值大宗产品，但长时间运行面临菌株突变退化和染菌风险。选择模式要综合考虑产物与生长的耦联关系、底物抑制和分离成本。
Batch fermentation charges everything at once, is simple and low-risk for contamination, and suits short cycles or products coupled to growth; fed-batch adds carbon source and other substrates as needed, avoiding substrate inhibition and extending the production phase, which makes it the mainstream choice for antibiotics, recombinant proteins and yeast. Continuous culture feeds and withdraws medium at matched rates to hold a productive steady state for long periods, fitting bulk low-margin products such as ethanol and single-cell protein, though prolonged runs risk strain degeneration and contamination. Mode selection weighs how product formation couples to growth, substrate inhibition and downstream separation cost.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Stanbury PF, Whitaker A, Hall SJ. Principles of Fermentation Technology, 3rd edition (Butterworth-Heinemann, 2017) 第2章与第9章
Stanbury PF, Whitaker A, Hall SJ. Principles of Fermentation Technology, 3rd edition (Butterworth-Heinemann, 2017), chapters 2 and 9
#发酵工程 #补料分批 #连续培养 #底物抑制
定向进化是如何在不了解酶结构的情况下改造酶性能的？
How does directed evolution improve an enzyme without understanding its structure?
定向进化模拟自然选择的循环：先用易错 PCR、DNA 重组或饱和突变在目标基因上产生大量变体文库，再建立与目标性能挂钩的筛选或选择方法，把优良变体的基因作为下一轮的模板反复迭代。关键在于筛选通量与目标的一致性，微孔板筛选、荧光激活细胞分选和体内互补选择分别适用于不同规模。该方法不依赖机理认识，已用于提高酶的热稳定性、改变底物特异性乃至创造自然界不存在的碳硅键形成反应，2018 年诺贝尔化学奖即表彰这一策略。
Directed evolution mimics cycles of natural selection: error-prone PCR, DNA recombination or saturation mutagenesis first build large variant libraries of the target gene, then a screen or selection tied to the desired property identifies winners whose genes template the next round. Success hinges on screening throughput and on how faithfully the assay reflects the goal, with microplate screening, fluorescence-activated cell sorting and in vivo complementation suiting different scales. Because no mechanistic insight is required, the approach has raised enzyme thermostability, redirected substrate specificity and even created carbon-silicon bond-forming reactions unknown in nature, work recognized by the 2018 Nobel Prize in Chemistry.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Arnold FH. Directed evolution: bringing new chemistry to life. Angewandte Chemie International Edition (2018) 57:4143-4148
Arnold FH. Directed evolution: bringing new chemistry to life. Angewandte Chemie International Edition (2018) 57:4143-4148
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1002/anie.201708408
#定向进化 #突变文库 #高通量筛选 #酶工程
由二氧化碳人工合成淀粉的路线是怎样构建的，意义何在？
How was an artificial route from carbon dioxide to starch constructed, and why does it matter?
中国科学院天津工业生物技术研究所团队在 2021 年报道了一条化学与酶催化耦联的人工淀粉合成路径：先用无机催化剂把二氧化碳氢化为甲醇，再由甲醇经甲醛、二羟基丙酮磷酸等中间体，通过十余个酶组成的模块转化为葡萄糖单元并聚合成淀粉。该路线只有约十一步核心反应，比植物光合作用固碳合成淀粉的天然途径大为简化，实验室条件下淀粉合成速率约为玉米的八点五倍。它验证了以工业尾气二氧化碳和绿氢为原料、脱离耕地生产粮食大分子的可行性，但能量效率和放大成本仍是主要挑战。
In 2021 a team at the Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, reported a hybrid chemical-enzymatic route to starch: an inorganic catalyst first hydrogenates carbon dioxide to methanol, and modules of about a dozen enzymes then convert methanol through formaldehyde and dihydroxyacetone phosphate into glucose units that are polymerized into starch. With roughly eleven core reactions the route is far simpler than the natural photosynthetic path, and under laboratory conditions its starch synthesis rate was about 8.5 times that of maize. It demonstrates that food macromolecules could in principle be made from industrial carbon dioxide and green hydrogen without farmland, though energy efficiency and scale-up cost remain the main obstacles.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：本题原挂出处与答案内容不符，已撤回；具体书目待补，暂不展示来源。
本题原挂出处与答案内容不符，已撤回；具体书目待补。
Previous citation withdrawn as unsupported for this answer; a specific source is pending.
#人工淀粉合成 #二氧化碳转化 #化学-酶耦联 #无细胞体系
第一代与第二代燃料乙醇在原料和技术上有什么差别？
How do first- and second-generation fuel ethanol differ in feedstock and technology?
第一代乙醇用甘蔗糖汁或玉米淀粉为原料，淀粉只需液化和糖化即可被酵母发酵，工艺成熟成本低，但与粮食生产争地争粮。第二代以秸秆、林业剩余物等木质纤维素为原料，需要先经蒸汽爆破或稀酸等预处理破坏木质素-半纤维素屏障，再用纤维素酶水解得到葡萄糖和木糖。其难点在于预处理能耗、酶成本以及酵母对木糖利用和抑制物耐受性不足，因此单位成本仍高于第一代。
First-generation ethanol uses sugarcane juice or maize starch, and starch only needs liquefaction and saccharification before yeast fermentation, giving a mature low-cost process that nonetheless competes with food production for land and grain. Second-generation ethanol uses lignocellulose such as straw and forestry residues, which must first be pretreated by steam explosion or dilute acid to break the lignin-hemicellulose barrier and then hydrolysed by cellulases to glucose and xylose. Its bottlenecks are pretreatment energy, enzyme cost and the limited ability of yeast to ferment xylose and tolerate inhibitors, so unit cost still exceeds the first generation.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Somerville C, Youngs H, Taylor C, Davis SC, Long SP. Feedstocks for lignocellulosic biofuels. Science (2010) 329:790-792
Somerville C, Youngs H, Taylor C, Davis SC, Long SP. Feedstocks for lignocellulosic biofuels. Science (2010) 329:790-792
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1126/science.1189268
#燃料乙醇 #木质纤维素 #预处理 #纤维素酶
木质纤维素为什么难以被酶降解，必须先预处理？
Why is lignocellulose so resistant to enzymatic degradation that pretreatment is required?
植物细胞壁的抗降解性是长期演化出的防御结构：纤维素链以大量氢键堆叠成高结晶度的微纤丝，酶难以接触内部糖苷键；半纤维素和木质素在外层交联包裹，木质素还会非特异吸附纤维素酶造成失活。此外底物比表面积小、孔径限制酶扩散，都降低水解速率。预处理通过蒸汽爆破、稀酸或碱处理去除或重排木质素与半纤维素、增加可及表面并降低结晶度，但过高强度会产生糠醛、乙酸等抑制发酵的降解产物，因此需要在可及性与抑制物生成之间权衡。
Cell-wall recalcitrance is an evolved defence: cellulose chains pack through extensive hydrogen bonding into highly crystalline microfibrils whose internal glycosidic bonds enzymes can hardly reach, while hemicellulose and lignin cross-link around them and lignin further adsorbs cellulases non-specifically and inactivates them. Low accessible surface area and pores that restrict enzyme diffusion further slow hydrolysis. Pretreatment with steam explosion, dilute acid or alkali removes or rearranges lignin and hemicellulose, increases accessible surface and lowers crystallinity, but harsh conditions generate furfural and acetic acid that inhibit fermentation, so accessibility must be traded off against inhibitor formation.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Himmel ME 等,《Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production》,Science 315: 804-807,2007 (DOI: 10.1126/science.1137016)
Himmel ME et al., 'Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production', Science 315: 804-807, 2007, DOI: 10.1126/science.1137016
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1126/science.1137016
#生物质抗降解性 #纤维素结晶度 #木质素 #抑制物